Suppression Of Rebound Research Articles

Optimal attitude control for landing on asteroid with a flexible lander

The recently developed flexible lander offers a potential option for future asteroid landing missions due to its advantages in suppression of rebound and overturning. The strong nonlinear dynamics and control constraints of the flexible lander hinder the online implementation of optimal attitude feedback control. To generate the optimal attitude control rapidly, a constrained inhomogeneous approximating sequence of Riccati equations (CI-ASRE) method is proposed. The saturation function is firstly constructed to incorporate control magnitude constraints into dynamics so that the constraints can be analytically handled. Subsequently, to avoid singularity, a partial factorization strategy is proposed to convert the constrained dynamics into two parts, a pseudolinear term and an inhomogeneous term. This factorization enables the nonlinear problem to be expressed as the limit of a sequence of inhomogeneous linear quadratic problems while avoiding local linearization. At last, the analytical CI-ASRE is newly derived to iteratively solve these problems to rapidly obtain optimal feedback control. The computational simplicity and effectiveness of the CI-ASRE method overcome difficulties of optimal attitude control problems of the flexible lander associated with control constraints, strong nonlinearity, and online feedback control generation. The effectiveness of the proposed method for the flexible lander is verified using a landing scenario on asteroid 433 Eros.

Abstract 1654: Anti-tumor activity of orally-available cyclic peptide LUNA18 through direct RAS inhibition in RAS-altered tumors

Abstract RAS is the one of the most frequently altered genes in human cancer and contributes to the growth of tumors. Recently, KRAS G12C inhibitors were approved as the first molecular targeting agents for RAS, but there are still huge unmet medical needs in RAS-mutated cancers because drugs targeting non-KRAS G12C tumors have not yet been approved and efficacy by even approved KRAS G12C inhibitors is not satisfactory. LUNA18 is the cyclic peptide that binds to RAS mutants and wildtype, including KRAS, NRAS and HRAS, thereby inhibiting protein-protein interaction (PPI) between the inactive form of RAS and GEFs (guanine nucleotide exchange factors). LUNA18 decreased the active form of KRAS and phosphorylated ERK and AKT, and cell proliferation in RAS-mutated cancer cells with nM order of cellular IC50s irrespective of tumor types and amino acid substitutions except for Q61 mutants. On the other hand, LUNA18 did not inhibit proliferation of cells with active mutations downstream of RAS (BRAF and MEK), suggesting LUNA18 selectively inhibited growth of RAS-dependent cells. Consistent with in vitro cellular activity, oral administration of LUNA18 showed durable RAS signal inhibition up to 24-48 hours and tumor regression in RAS-mutated xenograft models. In addition to KRAS-mutated cells, LUNA18 also showed in vitro and in vivo robust efficacy in KRAS-amplified cells. These data indicated LUNA18 is the versatile compound that selectively suppressed cellular signaling from RAS G12/G13 mutants as well as RAS wildtype amplification through inhibition of PPI between the inactive form of RAS and GEFs, and it can be applicable to a wide range of RAS-altered tumors. Rebound of the MAPK pathway is reported to be the one of the cause for attenuating efficacy of KRAS G12C inhibitors. We also observed the rebound of ERK activation 24-72 hours after the treatment with a KRAS G12C inhibitor in cells with the KRAS G12C mutation though suppression of KRAS activity was maintained. On the other hand, LUNA18 persistently suppressed ERK activity as well as KRAS activity up to 72 hours. The combination of the KRAS G12C inhibitor with siRNA for RAS wildtype showed durable inhibition of ERK activity, suggesting that RAS wildtype plays a key role for the rebound of ERK activity and inhibitory activity to RAS wildtype by LUNA18 contribute to the persistent inhibition of RAS signaling by LUNA18. We orally administered LUNA18 and a KRAS G12C inhibitor to a xenograft model, which showed temporal response and then acquired resistance to a KRAS G12C inhibitor, and found that LUNA18 significantly suppressed emergence of resistance to a KRAS G12C inhibitor. These results supported that the combination of the KRAS G12C inhibitor with LUNA18 could be a promising option to patients with KRAS G12C mutation by suppressing resistance to a KRAS G12C inhibitor through the suppression of rebound of the MAPK pathway. Citation Format: Hitoshi Sase, Saki Michisaka, Yukako Tachibana, Masami Hasegawa, Toshihiko Fujii, Kana Takei, Tomoko Kanei, Naoaki Murao, Shino Kuramoto, Norihito Shibahara, Atsushi Ohta, Mikimasa Tanada, Takuya Shiraishi, Hitoshi Iikura, Takehisa Kitazawa, Hiroshi Tanaka. Anti-tumor activity of orally-available cyclic peptide LUNA18 through direct RAS inhibition in RAS-altered tumors [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1654.

Parallel governing criteria for non-Newtonian droplet rebound suppression on superhydrophobic surfaces

Non-Newtonian droplets are known to suppress rebound on superhydrophobic (SH) surfaces. Our previous work (Dhar et al., Phys Rev Fluids, 2019, vol 4 [1]) showed that the polymer concentration and impact velocity must exceed a certain threshold to initiate the onset of rebound suppression. Analogous to drag reduction or elastic instabilities, we proposed that rebound suppression occurs only when the Weissenberg number exceeds unity (i.e., Wi >1) at the onset of retraction. In this study, we explore four different types of SH surfaces to examine the universality of the previous observation (the importance of Wi >1 for rebound suppression). We observed that rebound suppression does not occur on all types of SH surfaces. The surfaces where rebound suppression was observed are categorized as ‘Type-I’, while the remaining as ‘Type-II’. The non-uniformity in the rebound suppression phenomena is explained by the role of Cassie to Wenzel transformation (CWT) or impalement. We showed that for ‘Type-I’ surfaces, when the ratio of dynamic pressure (PD) to minimum capillary pressure (PC) exceeds unity (i.e., PD/PC > 1), the rebound is suppressed. The ‘Type-II’ surfaces have characteristic spacing in the order of nanometers, which is three orders of magnitude lower than the microtextured ‘Type-I’ surfaces. Thereby, the minimum capillary pressure is significantly higher for ‘Type-II’ surfaces. The dynamic pressure could not surpass the minimum capillary pressure for the impact velocities and polymer concentrations studied for the ‘Type-II’ surfaces. As PD/PC remained < 1, for ‘Type-II’ surfaces, rebound suppression was not observed. It must be noted that for the same values of PD/PC > 1 values, water droplets didn’t show rebound suppression on ‘Type-I’ surfaces. The non-Newtonian droplets are known to slow down the retraction dynamics due to normal stress, extensional viscosity and higher adsorption at the substrate. We have demonstrated the role of extensional viscosity in this study, particularly how strain stiffening of radial filaments emanating from the droplet aids in dissipating energy, which further aids in arresting drop rebound. Therefore, the existence of two parallel mechanisms: the role of fluid elasticity (manifested through Wi > 1), and the role of CWT or impalement (manifested through PD/PC> 1), are necessary conditions for non-Newtonian drop rebound suppression on superhydrophobic surfaces.

Suppression of hollow droplet rebound on super-repellent surfaces

Droplet rebound is ubiquitous on super-repellent surfaces. Conversion between kinetic and surface energies suggests that rebound suppression is unachievable due to negligible energy dissipation. Here, we present an effective approach to suppressing rebounds by incorporating bubbles into droplets, even in super-repellent states. This suppression arises from the counteractive capillary effects within bubble-encapsulated hollow droplets. The capillary flows induced by the deformed inner-bubble surface counterbalance those driven by the outer-droplet surface, resulting in a reduction of the effective take-off momentum. We propose a double-spring system with reduced effective elasticity for hollow droplets, wherein the competing springs offer distinct behavior from the classical single-spring model employed for single-phase droplets. Through experimental, analytical, and numerical validations, we establish a comprehensive and unified understanding of droplet rebound, by which the behavior of single-phase droplets represents the exceptional case of zero bubble volume and can be encompassed within this overarching framework.

Load rebound suppression strategy and demand response potential of thermal storage HVAC systems: An experimental and simulation study

The problem of power imbalance caused by the large power consumption of heating, ventilation and air-conditioning (HVAC) units in the summertime can be alleviated by building demand response (DR) strategies. However, after DR, load rebound will occur due to the sudden increase in demand. Meanwhile, there is a general lack of information on effective DR strategies. To study the DR potential and load rebound suppression strategies of HVAC systems, nine operation strategies were devised and applied experimentally. The physical experiments were conducted on a central air-conditioning system to investigate control strategies such as regional temperature reset, active energy storage, cold source unit activation and deactivation, as well as pre-cooling. Additionally, a simulation model was developed utilizing TRNSYS. DR evaluation indices, such as duration, power reduction capability, system operation cost, etc. were applied. The experimental results show that after a water storage tank is added as a buffer tank, the start and stop times of the air source heat pump were reduced from 46 to 6. Utilizing the thermal inertia of building and HVAC system, while ensuring personnel's thermal comfort, the DR participation time can be extended to 40–50 min. This will result in an 8.9 %–12.6 % reduction in power consumption. The simulation results show that with active energy storage added, HVAC system's DR participation time can be increased to about 120 min, the maximum power consumption can be reduced by 23.4 %, and the maximum operating cost can be reduced by 21.7 %. The study shows that a slow recovery strategy and the extension of DR control time can limit load rebound effectively. From the result of load rebound suppression effect, if the load rebound suppression strategy is not adopted, the power after DR will be 3.7 % higher than that pre-DR; the load rebound suppression strategy is adopted, which is 3.6 % lower than that pre-DR. By implementing the proposed DR strategies, the issue of frequent activation and deactivation of refrigeration units can be effectively mitigated. This will greatly alleviate the power supply and demand contradiction, while also effectively suppressing the load rebound effect to prevent a secondary peak in power consumption.

Droplet impact on hydrophobic and superhydrophobic surfaces with the electrowetting technique

A droplet impacting hydrophobic/superhydrophobic surfaces undergoes spreading, recoiling, and rebounding. All these phenomena are affected by the energy exchange between the impacting droplet and the surface. In the present work, an electrowetting technique is implemented to change the droplet interaction with the surface. The droplet impact on hydrophobic and superhydrophobic surfaces combined with alternating current electrowetting on dielectric (AC EWOD) has been numerically investigated. Droplet impact characteristics have been studied for various voltage amplitudes, frequencies, and surface hydrophobicities. These factors strongly affect the droplet dynamics of the impacting droplet. An increase in voltage amplitude enhances the maximum spreading of the impacting droplet. In contrast, it reduces the recoiling rate of the droplet, resulting in partial or complete suppression of the droplet rebound. At a particular voltage amplitude, frequency and hydrophobicity of the surface affect the droplet rebound suppression. Complete rebound suppression has been observed at higher voltage amplitudes and the medium range of frequencies (25–50 Hz). The contact time of the droplet decreases with the increase in surface hydrophobicity at all frequencies, whereas it increases with the voltage amplitude. Contact line velocity and velocity inside the droplet manifest the inertia of the droplet. The droplet is unable to rebound if velocities are very low.

Triggering of electro-elastic anti-superhydrophobicity during non-Newtonian droplet collision

The present article discusses the electrohydro-dynamics of impacting non-Newtonian dielectric droplets on superhydrophobic (SH) surfaces. The role of important parameters like electric Eotvos number ( Eo e ), Weber number ( We ), dielectric particle concentration ( TiO 2 ) and polymer concentration ( PEG-400 ) were elucidated in this experimental study. Due to the interplay of non-Newtonian effects and electric field, we had observed the suppression of drop rebound on SH surfaces at much lower Eo e compared to its Newtonian counterpart. It has been observed that with an increase in both polymer concentration or dielectric particle concentration, the suppression of drop rebounds was observed at lower Eo e. In order to encapsulate the combined effects of electric field and non-Newtonian dynamics on drop rebound suppression, we have introduced the ‘electro-elastic effect’. Contrary to the common observations of drop rebound on SH surfaces, this electro-elastic effect induces inhibition of drop rebound, thereby resulting in anti-superhydrophobicity. Subsequently, we also established a scaling relationship to show that the rebound suppression is observed as a manifestation of the onset of electro-elastic instability, when a proposed electric Weissenberg number ( Wi e ) exceeds unity. Finally, we demarcated the rebound and rebound suppression regimes of droplet dynamics through a detailed phase map.

Spectacular Behavior of a Viscoelastic Droplet Impinging on a Superhydrophobic Mesh.

Spray formation using the droplet impact on superhydrophobic mesh surfaces is particularly important because of its application in different industries. The present study revealed that adding a trivial amount of the poly(ethylene oxide) (PEO) polymer to a water droplet can considerably change the impact phenomena on the superhydrophobic mesh surfaces and suppress the spray formation. Droplet rebound is observed only in a narrow range of impact velocities of PEO aqueous droplets when the tiny filaments still connect the surface and droplet. Rebound suppression and deposition of the PEO aqueous droplet is attributed to the higher interaction between the polymer chains and the superhydrophobic mesh surface. After a critical impact velocity and We number which is independent of the PEO concentration, the liquid penetrates the mesh pores. The penetrated liquid formed the ligaments that grow until they reach the maximum length and surprisingly retract back to the mesh surface and the mother droplet. The ligaments destabilized at low PEO concentrations (c = 0.5 and 1 g/L) and a mesh opening size of H = 357 μm to the crest swell droplets when the droplet size is reduced by increasing the impact velocity. The ligament fragmentation and droplet detachment are observed only at high impact velocities when c = 0.5 and 1 g/L and H = 357 μm. The result shows that the PEO additive does not significantly affect the maximum spreading diameter. An empirical model to calculate the maximum spreading factor is developed.

Genetic Algorithm Based Temperature-Queuing Method for Aggregated IAC Load Control

In recent years, demand response (DR) has played an increasingly important role in maintaining the safety, stability and economic operation of power grid. Due to the continuous running state and extremely fast speed of response, the aggregated inverter air conditioning (IAC) load is considered as the latest and most ideal object for DR. However, it is easy to cause load rebound when the aggregated IAC load participates in DR. Existing methods for controlling air conditioners to participate in DR cannot meet the following three requirements at the same time: basic DR target, load rebound suppression, and users’ comfort. Therefore, this paper has proposed a genetic algorithm based temperature-queuing control method for aggregated IAC load control, which could suppress load rebound under the premise of ensuring the DR target and take users’ comfort into account. Firstly, the model of the aggregated IAC load is established by the Monte Carlo method. Then the start and end time of DR are selected as the main solution variables. A genetic algorithm is used as the solving tool. The simulation results show that the proposed strategy shows better performance in suppressing load rebound. In the specific application scenario of adjusting the frequency fluctuation of the microgrid, the results of the case show that this strategy can effectively control the frequency fluctuation of the microgrid. The effectiveness of the strategy is verified.

Magneto-Elastic Effect in Non-Newtonian Ferrofluid Droplets Impacting Superhydrophobic Surfaces.

In this article, we propose, with the aid of detailed experiments and scaling analysis, the existence of magneto-elastic effects in the impact hydrodynamics of non-Newtonian ferrofluid droplets on superhydrophobic surfaces in the presence of a magnetic field. The effects of magnetic Bond number (Bom), Weber number (We), polymer concentration, and magnetic nanoparticle (Fe3O4) concentration in the ferrofluids were investigated. In comparison to Newtonian ferrofluid droplets, addition of polymers caused rebound suppression of the droplets relatively at lower Bom for a fixed magnetic nanoparticle concentration and We. We further observed that for a fixed polymer concentration and We, increasing magnetic nanoparticle concentration also triggers earlier rebound suppression with increasing Bom. In the absence of the magnetic nanoparticles, the non-Newtonian droplets do not show rebound suppression for the range of Bom investigated. Likewise, the Newtonian ferrofluids show rebound suppression at large Bom. This intriguing interplay of elastic effects of polymer chains and the magnetic nanoparticles, dubbed as the magneto-elastic effect, is noted to lead to the rebound suppression. We establish a scaling relationship to show that the rebound suppression is observed as a manifestation of the onset of magneto-elastic instability only when the proposed magnetic Weissenberg number (Wim) exceeds unity. We also put forward a phase map to identify the various regimes of impact ferrohydrodynamics of such droplets and the occurrence of the magneto-elastic effect.

Elasto-hydrodynamics of non-Newtonian droplet collision with convex substrates

In this article, we report the post-collision elasto-hydrodynamics of non-Newtonian elastic or Boger fluid droplets [polyacrylamide (PAAM) solution in water] on convex or cylindrical targets of various diameters. Both hydrophilic and superhydrophobic (SH) surfaces were studied to deduce the role of wettability. Different governing parameters, such as cylinder diameter, Weber number, and fluid elasticity (different polymer concentrations), were systematically varied to understand various hydrodynamic outcomes. In contrast to the Newtonian water droplets on hydrophilic surfaces, PAAM droplets resisted capillary breakup and exhibited formation of long lasting, slender, fluid filaments. In certain cases, these filaments showed the existence of satellite beads during stretching, which are generated through blistering or pearling instability (known as beads-on-a string). In the case of SH surfaces, PAAM droplets rebound at larger cylindrical diameters and higher Weber number compared to water. Thin transient filaments attached to the cylinder surface eventually suppress droplet rebound. Such rebound suppression is essentially a non-Newtonian feature, as water droplets on a cylindrical SH surface always exhibited rebound and fragmentation. Finally, we illustrate phase maps where the different regimes of post-impact elasto-hydrodynamics are correlated as functions of a proposed elastic Weber number (which incorporates the effects of both the Weber and the Weissenberg numbers) and the non-dimensional diameter D*. We show that distinct scaling regimes appear in the elasto-hydrodynamic behavior of the post-impact droplets of elastic fluids.

Origin of Rebound Suppression for Dilute Polymer Solution Droplets on Superhydrophobic Substrate.

Controlling droplet deposition with a minute amount of polymer additives is of profound practical importance in a wild range of applications. Previous work ascribed the relevant mechanisms to extensional viscosity, normal stress, wetting properties, etc., but the mechanism remains controversial. In this paper, we employ molecular dynamics simulations systematically for the first time to investigate the origin of rebound suppression for dilute polymer solution droplets on a flat superhydrophobic substrate. The results demonstrate that polymer-substrate interactions and impact velocities dominate the antirebound phenomenon. For low impact velocities, the dynamic characteristics of droplets are insensitive to polymer additives. However, large impact velocities will enhance the stretch behavior of polymer chains and make the chains closer to the substrate, increasing the probability of polymer molecules contacting the bottom substrate. With the cooperation of strong polymer-substrate interactions, polymer molecules can be absorbed easily by the bottom substrate, resisting the retraction process and leading to the onset of the antirebound behavior.

Rebound Suppression of a Droplet Impacting on a Supersolvophobic Surface by a Small Amount of Polymer Additives.

A small amount of polymer dissolved in a droplet suppresses droplet rebound when it impinges on a supersolvophobic surface. This work investigates impacting dynamics of a droplet of dilute polymer solution depending on the molecular weight and the concentration of the polymer by using multibody dissipative particle dynamics simulations. Either the long polymer or the high polymer concentration suppresses rebound of a droplet although its shear viscosity and the liquid-vapor surface tension are not different from those of a pure solvent droplet. We found a new mechanism of the anti-rebound in which the resistance is applied against the hopping motion, while behavior of the non-rebounding droplet at the earlier spreading and retraction stages is the same as for the rebounding droplets. Two polymer contributions to reducing the rebound tendency are quantitatively analyzed: the alteration of the substrate wettability by the polymer adsorption and the polymer elongation force.

Promoting rebound of impinging viscoelastic droplets on heated superhydrophobic surfaces

The rebound of impinging droplets is a defining characteristic of superhydrophobic surfaces; yet, such an intriguing interfacial phenomenon can be effectively suppressed by adding a tiny amount of flexible polymers to induce non-Newtonian viscoelastic properties. In this work, however, we demonstrate the promoting effects of surface heating on the rebound of impinging viscoelastic droplets on superhydrophobic surfaces. The underlying mechanism for the promotion is that the local heat transfer at the liquid–solid interface causes the fast evaporation of the liquid and thus the breakup of the formed viscoelastic filaments, which hinder droplet recoiling. Therefore, the lower threshold velocity for rebound increases while the upper threshold velocity for rebound suppression decreases with increasing surface temperature, resulting in a wider regime for droplet rebound in the impact phase diagram. The surface heating effect on liquid–solid interactions also leads to a nontrivial dependence of the contact time on the impact velocity and a linear decrease of the restitution coefficient with the Weber number for diverse bouncing viscoelastic droplets, which can be rationalized by coupling the interfacial force and energy analyses. We envision that these findings would be useful in technological processes requiring control the retention of viscoelastic liquids on solid surfaces.

Conceptual Study on Robust Rebound Suppression Mechanism for Small-Body Landing

Landing on celestial bodies typically includes a free fall to the body surface and requires energy dissipation. Landing sites can exhibit many uncertainties, especially in surface parameters. Therefore, robustness is required irrespective of variations in landing conditions. Conventional mechanisms, such as shock absorbers or airbags, have repeatedly achieved safe landings; however, they are not reusable in the ground-verification phase and cause complexity. This study proposes a robust, lightweight, and simple rebound suppression mechanism with reusability in the ground verification phase by simultaneously considering the characteristics of mechanical energy and momentum exchange aspects. The design characteristics are clarified mainly through numerical discussions, and the effectiveness of the proposed mechanism is demonstrated in comparison to existing momentum exchange mechanisms. The results show a promising rebound suppression capability compared with those of the previously suggested mechanisms and an improvement in robustness against uncertainties. A case study is also shown to verify the proposed mechanism’s effectiveness. Numerical simulation results for a fictional landing mission created from real microgravity landers show that the proposed mechanism achieves the energy dissipation requirement, combined with the plastic deformation mechanism of the shock-absorbing material.

Onset of rebound suppression in non-Newtonian droplets post-impact on superhydrophobic surfaces

Droplet deposition after impact on superhydrophobic surfaces has been an important area of study in recent years for its potential application in reduction of pesticides usage. Minute numbers of long-chain polymers added to water have been known to arrest the droplet rebound effect on superhydrophobic surfaces. Previous studies have attributed different reasons like extensional viscosity, dominance of elastic stresses, or slowing down of the contact line in the retraction phase due to stretching of polymer chains. The present study attempts to unravel the existence of critical criteria of polymer concentration and impact velocity on the inhibition of droplet rebound. The impact velocity will indirectly influence the shear rate during the retraction phase, and the polymer concentration dictates the relaxation timescale of the elastic fluids. Finally, we show that the governing Weissenberg number (at onset of retraction), which quantifies both the elastic effects of polymer chains and the hydrodynamics, is the critical parameter in determining the regime of onset of rebound suppression, and that there is a critical value which determines the onset of bounce arrest. The previous three causes, which are manifestations of elastic effects in non-Newtonian fluids, can be related to the proposed Weissenberg number criterion.1 MoreReceived 4 April 2019DOI:https://doi.org/10.1103/PhysRevFluids.4.103303©2019 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasDrop & bubble phenomenaNon-Newtonian fluidsPropertiesViscoelasticityFluid Dynamics

Evidence for Modulation of Oxygen Rebound Rate in Control of Outcome by Iron(II)- and 2-Oxoglutarate-Dependent Oxygenases.

Iron(II)- and 2-oxoglutarate-dependent (Fe/2OG) oxygenases generate iron(IV)-oxo (ferryl) intermediates that can abstract hydrogen from aliphatic carbons (R-H). Hydroxylation proceeds by coupling of the resultant substrate radical (R•) and oxygen of the Fe(III)-OH complex ("oxygen rebound"). Nonhydroxylation outcomes result from different fates of the Fe(III)-OH/R• state; for example, halogenation results from R• coupling to a halogen ligand cis to the hydroxide. We previously suggested that halogenases control substrate-cofactor disposition to disfavor oxygen rebound and permit halogen coupling to prevail. Here, we explored the general implication that, when a ferryl intermediate can ambiguously target two substrate carbons for different outcomes, rebound to the site capable of the alternative outcome should be slower than to the adjacent, solely hydroxylated site. We evaluated this prediction for (i) the halogenase SyrB2, which exclusively hydroxylates C5 of norvaline appended to its carrier protein but can either chlorinate or hydroxylate C4 and (ii) two bifunctional enzymes that normally hydroxylate one carbon before coupling that oxygen to a second carbon (producing an oxacycle) but can, upon encountering deuterium at the first site, hydroxylate the second site instead. In all three cases, substrate hydroxylation incorporates a greater fraction of solvent-derived oxygen at the site that can also undergo the alternative outcome than at the other site, most likely reflecting an increased exchange of the initially O2-derived oxygen ligand in the longer-lived Fe(III)-OH/R• states. Suppression of rebound may thus be generally important for nonhydroxylation outcomes by these enzymes.

Evaluating energy supply service reliability for commercial air conditioning loads from the distribution network aspect

The limited amount of dispatching flexibility has encouraged the development and implementation of demand response in the distribution system. Commercial air conditioning loads are promising demand response resources and tend to have greater potential for centralized regulation. From the perspective of distribution networks, evaluating the reliability of energy supply services for air conditioning loads should be of much concern because reliable services would directly affect the customers’ tendency to demand response. However, traditional load reliability evaluation does not fully explore the fact that the energy supply processes of air conditioning loads can be flexible. Modeling the energy demands as flexible loads, a reliability assessment algorithm for commercial air conditioning loads is proposed for distribution systems in this paper. The “loss of load” event is innovatively defined considering customer preferences. Novel systematic indices are established that are specialized for describing the reliability of energy supply services. Afterward, a two-stage control strategy is proposed considering the comfort requirements of customers, which would affect reliability performance. The first stage optimizes the operating state of the air conditioning system internal equipment collaboratively, while the second stage sacrifices some comfort for sufficient utilization of the thermal self-storage capacity and load rebound suppression. Finally, the proposed method is validated in a standard test system with voltage violation risks. The results demonstrate the impacts of different control strategies on the reliability performance of commercial air conditioning loads. Analysis drawn from the sensitivity of load reliability indices can assist distribution system operators in coordinating energy supply reliability and dispatching requirements.

A Self-Adaptive Stiffness Approach to Improving the Robustness of Electrostatic Switches Against Parameter Variations

The “soft-landing” effect during the closure of RF-MEMS switches is crucial for improving their reliability. However, the rebound suppression effectiveness has rather poor robustness against the dimension deviations and waveform distortions resulting from micro-fabrication tolerance, wear and tear, and circuit aging in the device’s life-cycle. In contrast to the traditional constant stiffness system, this letter proposes a novel self-adaptive stiffness approach, whereby the system’s stiffness increases markedly with increasing displacement so that its elastic potential energy against the electrostatic energy is mainly concentrated in the region near the closing position for a better rebound suppression. Our experiments show that, for an ensemble of fabricated devices subjected to the unified dual-pulse actuation waveform, the reliable working gap range of the new approach ( $1.4~\mu \text{m}$ ) in which the switches can be closed completely, is 4.6 times larger than that of the constant stiffness scheme ( $0.3~\mu \text{m}$ ). In addition, for the actuation voltage and pulse time with variations of up to ±10%, this new approach shows significantly reduced closure time and bounce.

運動量交換を主体とした水平移動体の衝突リバウンド抑制制御

運動量交換を主体とした水平移動体の衝突リバウンド抑制制御