Reactive Synthesis Research Articles

Structural Synthesis of PLC Program for Real-Time Specification Patterns

Among all the reactive synthesis methods, the results of the structural synthesis have the best interpretability and traceability. However, existing structural synthesis method cannot deal with real-time specifications and specifications with circular dependencies. A structural synthesis method for Programmable Logic Controller programs is proposed. First, a real-time specification pattern language, RTSPS4Syn, is proposed. Under the condition that there is no circular dependency between the specification items, the implementations of a specification item are assembled structurally from the implementation of its scope and property expression; and the programs for the specification items are concatenated according to the order of priority and dependency to obtain the synthesized program. This paper presents a method to eliminate the circular dependence of specifications, such that the synthesis approach can be applied to specifications with circular dependency. Furthermore, this paper presents an approach for setting the preset values of timers when considering tolerance on the duration of the delay. The synthesis method does not need to check the conflict and determine the nondeterministic part of the specifications. These problems are solved in existing research by constraint solving in PSPACE.

Reactive Extrusion Synthesis of Biobased Isocyanate-Free Hydrophobically Modified Ethoxylated Urethanes with Pendant Hydrophobic Groups.

Development of hydrophobically modified ethoxylated urethane (HEUR) rheology modifiers enabled the widespread application of waterborne paints and coatings, replacing their environmentally burdening solvent-based predecessors. However, the diisocyanates, required for the conventional synthesis of HEURs, pose severe eco-sustainability threats. In this paper, we demonstrate an innovative approach to avoiding toxic components in the preparation of rheology modifiers by obtaining a new class of water-soluble isocyanate-free hydrophobically modified ethoxylated poly(hydroxy-urethane)s (IFHEURs). The first step in the synthetic pathway was the preparation of CO2-based five-membered poly(ethylene glycol) bis(cyclic carbonate) and its subsequent aminolysis using 4,7,10-trioxa-1,13-tridecanediamine, yielding poly(hydroxy-urethane) (PHU) prepolymers terminated with cyclic carbonate groups. The PHU prepolymers were further extended in a reactive extrusion (REX) synthesis using biobased hydrophobic diamine PRIAMINE 1075. The REX technique made it possible to overcome the typical limitations of the aminolysis reaction and to reach the desired conversion within a moderate reaction time. IFHEURs have been structurally elucidated using FT-IR and NMR spectroscopy techniques, MALDI-ToF mass spectrometry, and SEC analysis and applied as rheology modifiers. The study of their associative behavior in aqueous solutions confirmed that the architectural flexibility of the obtained IFHEURs, containing terminal and pendant hydrophobic groups, opens a perspective for tuneable thickening performance.

Porous MoAlB ceramic via reactive synthesis: Reaction mechanism, pore structure, mechanical property and high temperature oxidation behavior

Porous MoAlB ceramics were synthesized by an activation reaction sintering technique using Mo, Al and B powders as starting materials. The phase transformation, pore forming mechanism and the development of microstructure of porous MoAlB were discussed. MoAlB in pure phase was obtained at 1000 °C. The effects of Kirkendall effect and phase transformation are related to the changes of pore size, open porosity and expansion of porous MoAlB during the sintering process. The mechanical properties test shows that porous MoAlB ceramic has excellent processability and tensile strength. The oxidation test exhibits that porous MoAlB ceramic exhibits good oxidation resistance at high temperatures.

Improving oxidation resistance of porous FeAl-based intermetallics with high boron/yttrium alloying

The coalloying with high contents of chromium (Cr), boron (B) and yttrium (Y) for porous B2-structured FeAl intermetallics fabricated through reactive synthesis was conducted. The oxidation behaviors of porous FeAl-based materials were investigated by evaluating the pore-structure evolution, oxidation kinetics and oxide-scale configuration. The results show that with the coalloying of high contents of Cr, B and Y, the oxidation mass gains of porous FeAl materials at 600−800 °C are significantly reduced. The combination of B enriched on the surface of oxide scales and Y located at the scale−metal interface promotes the formation of thin protective nodular α-Al2O3 oxide scales. It is indicated that introducing relatively high contents of reactive elements such as B and Y can benefit the selective growth of α-Al2O3 scales at relatively low temperatures without pre-treatment.

High‐temperature reactive synthesis of the Zr–Ta multiboride with a supercomposite structure

AbstractThis study reports the formation of a ceramic composite consisting only of boride phases with an artificially created hierarchical superstructure. Such a composite was formed during the reaction‐driven consolidation process using a mixture of ZrB2, tantalum, and amorphous boron powders. The homogeneity of the reaction among these powders at 1900°C allowed the forming of a highly reproducible and repetitive superstructure where Ta3B4 forms a chain‐like mesh that entraps the ZrB2, ZrB, TaB, and (Zr,Ta)B2 phases. The multiboride ceramic composite exhibited extremely high hardness: 28.6 ± 3.2 or 22.6 ± 0.6 GPa. These were estimated using 98‐ and 196‐N loads, respectively. At 2000°C, the multiboride composite showed a strength of nearly 400 MPa and fractured in an elastic manner at the loading rate of 2.5 mm/min. This level of strength is usually observed for the bulk zirconium diboride at room temperature. The main factors leading to the improvement of the mechanical properties were considered to be the formation of the (Zr,Ta)B2 solid solution as well the composite structure.

Effect of Sn Content on the Pore Structures of Porous Ni-Sn Alloys Produced by Reactive Synthesis Sintering Method

Effect of Sn Content on the Pore Structures of Porous Ni-Sn Alloys Produced by Reactive Synthesis Sintering Method

Specification decomposition for reactive synthesis

Reactive synthesis is the task of automatically deriving a correct implementation from a specification. It is a promising technique for the development of verified programs and hardware. Despite recent advances in terms of algorithms and tools, however, reactive synthesis is still not practical when the specified systems reach a certain bound in size and complexity. In this paper, we present a sound and complete modular synthesis algorithm that automatically decomposes the specification into smaller subspecifications. For them, independent synthesis tasks are performed, significantly reducing the complexity of the individual tasks. Our decomposition algorithm guarantees that the subspecifications are independent in the sense that completely separate synthesis tasks can be performed for them. Moreover, the composition of the resulting implementations is guaranteed to satisfy the original specification. Our algorithm is a preprocessing technique that can be applied to a wide range of synthesis tools. We evaluate our approach with state-of-the-art synthesis tools on established benchmarks: the runtime decreases significantly when synthesizing implementations modularly.

The Before, During, and After of Multi-robot Deadlock

Collision avoidance for multi-robot systems is a well-studied problem. Recently, control barrier functions (CBFs) have been proposed for synthesizing controllers that guarantee collision avoidance and goal stabilization for multiple robots. However, it has been noted that reactive control synthesis methods (such as CBFs) are prone to deadlock, an equilibrium of system dynamics that causes the robots to stall before reaching their goals. In this paper, we analyze the closed-loop dynamics of robots using CBFs, to characterize controller parameters, initial conditions, and goal locations that invariably lead the system to deadlock. Using tools from duality theory, we derive geometric properties of robot configurations of an N robot system once it is in deadlock and we justify them using the mechanics interpretation of KKT conditions. Our key deductions are that (1) system deadlock is characterized by a force equilibrium on robots and (2) deadlock occurs to ensure safety when safety is at the brink of being violated. These deductions allow us to interpret deadlock as a subset of the state space, and we show that this set is non-empty and located on the boundary of the safe set. By exploiting these properties, we analyze the number of admissible robot configurations in deadlock and develop a provably correct decentralized algorithm for deadlock resolution to safely deliver the robots to their goals. This algorithm is validated in simulations as well as experimentally on Khepera-IV robots For an interactive version of this paper, please visit https://arxiv.org/abs/2206.01781.

Reactive synthesis of software robots in RPA from user interface logs

Robotic Process Automation (RPA) is an emerging technology in the field of Business Process Management (BPM) that enables the automation of intensive repetitive tasks (or simply routines). RPA solutions access the user interface (UI) layer of software (SW) applications and provide a virtual workforce of SW robots that are able to mimic human keyboard and mouse interactions with a UI as if a real person was doing them. To take full advantage of this technology, organizations leverage the support of skilled human experts that preliminarily observe how routines are executed on the UI of the involved SW applications, and then implement the executable RPA scripts required to automate the routines enactment by SW robots on a target computer system. However, the current practice is time-consuming and error-prone, as it strongly relies on the ability of the human experts to correctly interpret the routines (and their variants) to automate. In this paper, to tackle this issue, we use a design science research method to develop an approach, called SmartRPA, which is able to interpret the UI logs keeping track of many routine executions, and to automatically synthesize SW robots that emulate the most suitable routine variant for any specific intermediate user input that is required during the routine execution. The approach is implemented as an open-source tool and evaluated with four non-functional requirements employing both syntectic and real-world data.

Synthesis from Satisficing and Temporal Goals

Reactive synthesis from high-level specifications that combine hard constraints expressed in Linear Temporal Logic (LTL) with soft constraints expressed by discounted sum (DS) rewards has applications in planning and reinforcement learning. An existing approach combines techniques from LTL synthesis with optimization for the DS rewards but has failed to yield a sound algorithm. An alternative approach combining LTL synthesis with satisficing DS rewards (rewards that achieve a threshold) is sound and complete for integer discount factors, but, in practice, a fractional discount factor is desired. This work extends the existing satisficing approach, presenting the first sound algorithm for synthesis from LTL and DS rewards with fractional discount factors. The utility of our algorithm is demonstrated on robotic planning domains.

Microstructure and properties of Y2O3/Cu composites fabricated by a novel liquid phase in situ reactive synthesis process

Cu–Y2O3 composites were prepared by a secondary mechanical ball milling process and liquid phase in situ reaction and then sintered by the spark plasma sintering (SPS) consolidation technique. The microstructure and mechanical properties were studied using an X-ray powder diffractometer, scanning electron microscope, tensile tester, and Vickers hardness tester. The results showed that the added yttrium was converted into Y2O3, and the obtained Y2O3 nano-particles were uniformly distributed in the copper matrix, their mean size was 5.0 nm, and the cubic Y2O3 phase was coherent with the copper matrix, which indicated (422)Y2O3// (1‾11) Cu and [011‾] Y2O3// [11‾2] Cu orientation relationship. With the addition of Y, the mechanical properties of the composite materials were improved, and the hardness of 10 vol% Y2O3 was increased by 192.0%. Its tensile strength increased by 168.2% compared to pure copper.

Antibody-Mediated LILRB2-Receptor Antagonism Induces Human Myeloid-Derived Suppressor Cells to Kill Mycobacterium tuberculosis.

Tuberculosis is a leading cause of death in mankind due to infectious agents, and Mycobacterium tuberculosis (Mtb) infects and survives in macrophages (MФs). Although MФs are a major niche, myeloid-derived suppressor cells (MDSCs) are an alternative site for pathogen persistence. Both MФs and MDSCs express varying levels of leukocyte immunoglobulin-like receptor B (LILRB), which regulate the myeloid cell suppressive function. Herein, we demonstrate that antagonism of LILRB2 by a monoclonal antibody (mab) induced a switch of human MDSCs towards an M1-macrophage phenotype, increasing the killing of intracellular Mtb. Mab-mediated antagonism of LILRB2 alone and its combination with a pharmacological blockade of SHP1/2 phosphatase increased proinflammatory cytokine responses and phosphorylation of ERK1/2, p38 MAPK, and NF-kB in Mtb-infected MDSCs. LILRB2 antagonism also upregulated anti-mycobacterial iNOS gene expression and an increase in both nitric oxide and reactive oxygen species synthesis. Because genes associated with the anti-mycobacterial function of M1-MФs were enhanced in MDSCs following mab treatment, we propose that LILRB2 antagonism reprograms MDSCs from an immunosuppressive state towards a pro-inflammatory phenotype that kills Mtb. LILRB2 is therefore a novel therapeutic target for eradicating Mtb in MDSCs.

N6‐methyladenosine‐RNA methylation promotes expression of solute carrier family 7 member 11, an uptake transporter of cystine for lipid reactive oxygen species scavenger glutathione synthesis, leading to hepatoblastoma ferroptosis resistance

<i>N</i>⁶‐methyladenosine‐RNA methylation promotes expression of solute carrier family 7 member 11, an uptake transporter of cystine for lipid reactive oxygen species scavenger glutathione synthesis, leading to hepatoblastoma ferroptosis resistance

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

Specifiable robustness in reactive synthesis

When synthesizing a system from a given specification, there is room for automatically adding various requirements, hence improving the resulting system. One such requirement covered extensively in past literature is that of robustness. In particular, the system can fail to read the inputs correctly from the environment, and the environment can fail to satisfy our assumptions about its behavior. Nevertheless, we want the system to still satisfy the specification even under these failures, in some limited way. It has to be limited because it is typically too strong of a requirement to realize the property regardless of the inputs and the environment’s assumptions. In this work, we propose a simple and flexible framework for synthesizing robust systems, where the user defines the required robustness via a temporal robustness specification. For example, the user may specify that the environment is eventually reliable, or input misreadings cannot occur more than k consecutive steps and synthesize a system under this assumption. Furthermore, our framework enables us to specify a temporal recovery specification, which describes how the designer expects the system to recover after a failure of the environment assumptions. We show examples of robust systems that we synthesized with this method using our synthesis tool Party.

Compositional synthesis of modular systems

In contrast to the breakthroughs in reactive synthesis of monolithic systems, distributed synthesis is not yet practical. Compositional approaches can be a key technique for scalable algorithms. Here, the challenge is to decompose a specification of the global system into local requirements on the individual processes. In this paper, we present and extend a sound and complete compositional synthesis algorithm that constructs for each process, in addition to the strategy, a certificate that captures the necessary interface between the processes. The certificates define an assume-guarantee contract that allows for formulating individual process requirements. By bounding the size of the certificates, we then bias the synthesis procedure towards solutions that are desirable in the sense that they have a small interface. We have implemented our approach and evaluated it on scalable benchmarks: It is much faster than standard methods for distributed synthesis as long as reasonably small certificates exist. Otherwise, the overhead of synthesizing additional certificates is small.

Live synthesis

Synthesis automatically constructs an implementation that satisfies a given logical specification. In this paper, we study the live synthesis problem, where the synthesized implementation replaces an already running system. In addition to satisfying its own specification, the synthesized implementation must guarantee a sound transition from the previous implementation. This version of the synthesis problem is highly relevant in “always-on” applications, where updates happen while the system is running. To specify the correct handover between the old and new implementation, we introduce an extension of linear-time temporal logic (LTL) called LiveLTL. A LiveLTL specification defines separate requirements on the two implementations and ensures that the new implementation satisfies, in addition to its own requirements, any obligations left unfinished by the old implementation. For specifications in LiveLTL, we show that the live synthesis problem can be solved within the same complexity bound as standard reactive synthesis, i.e., in 2EXPTIME. Our experiments show the necessity of live synthesis for LiveLTL specifications created from benchmarks of SYNTCOMP and robot control.

Effect of magnesium in breaking the correlation between reaction speed and intensity in the fabrication of TiAl3 intermetallics

When TiAl3 intermetallics were fabricated by the reactive synthesis of titanium and aluminum powder, the correlation between the speed and intensity of the reaction was stable. The magnesium-addition method with the addition of trace magnesium broke this correlation for the first time. Magnesium controlled the reaction in three stages in different ways: the initial melting and reaction area, the dynamic equilibrium formed by the diffusion rate consistent with the liquidus, and the high flowability eutectic liquid phase. The diffusion state of magnesium in each stage and the eutectic liquid phase formed with aluminum were the critical factors.

Synthesis of strategies for autonomous surveillance on adversarial targets

We study the problem of synthesizing a controller for an agent with imperfect sensing and a quantitative surveillance objective, that is, an agent is required to maintain knowledge of the location of a moving, possibly adversarial target. We formulate the problem as a one-sided partial-information game with a winning condition expressed as a temporal logic specification. The specification encodes the quantitative surveillance requirement as well as any additional tasks. Solving a partial-information game typically involves transforming it into a perfect-information belief game using a belief-set construction. Such a transformation leads to a state-space explosion, rendering the belief game computationally intractable to solve for most realistic settings. We present a belief-set abstraction technique to transform the partial-information game to a provably sound abstract belief game that can be solved efficiently using off-the-shelf reactive synthesis tools. We introduce a counterexample-guided refinement approach to automatically achieve the abstraction precision sufficient to synthesize a strategy that is provably winning on the original partial-information game. We evaluate the proposed method on multiple case-studies, implemented on hardware as well as high-fidelity ROS/Gazebo simulations where the agent must respond in real-time to a human-controlled adversary.

Reactive Sintering of Dysprosium-Iron Garnet via a Perovskite-Hematite Solid State Reaction and Physical Properties of the Material.

In this paper, we report on a successful synthesis of dysprosium iron garnet Dy3Fe5O12 (DyIG) by a reactive synthesis method involving dysprosium iron perovskite and hematite. Phase formation was traced using dilatometry, and XRD measurements attested to the formation of the desired structure. Samples with relative density close to 97% were fabricated. The samples were characterized using vibrating sample magnetometry, dielectric spectroscopy, and UV-Vis-NIR spectroscopy. Magnetic properties were probed in temperatures between 80 and 700 K with a maximum applied field of 1 kOe. The measurements revealed several effects: the compensation of magnetic moments at a certain temperature, the inversion of the magnetocaloric effect, and the ability to measure the Curie temperature of the material. Activation energy was determined from UV-Vis-NIR and dielectric spectroscopy measurements. Characteristic magnetic temperatures and activation energy values of the samples were similar to bulk DyIG obtained using other methods.