SuPerPM: A Large Deformation-Robust Surgical Perception Framework Based on Deep Point Matching Learned from Physical Constrained Simulation Data

Manipulation of tissue with surgical tools often results in large deformations that current methods in tracking and reconstructing algorithms have not effectively addressed. A major source of tracking errors during large deformations stems from wrong data association between observed sensor measurements with previously tracked scene. To mitigate this issue, we present a surgical perception framework, SuPerPM, that leverages learning-based non-rigid point cloud matching for data association, thus accommodating larger deformations. The learning models typically require training data with ground truth point cloud correspondences, which is challenging or even impractical to collect in surgical environments. Thus, for tuning the learning model, we gather endoscopic data of soft tissue being manipulated by a surgical robot and then establish correspondences between point clouds at different time points to serve as ground truth. This was achieved by employing a position-based dynamics (PBD) simulation to ensure that the correspondences adhered to physical constraints. The proposed framework is demonstrated on several challenging surgical datasets that are characterized by large deformations, achieving superior performance over state-of-the-art surgical scene tracking algorithms.Comment: Under review for ICRA202

Utjecaj lantana na mikrostrukturu i svojstva čelika ASTM A216

In order to satisfy the rudder horn casting standards of the International Association of Classification Societies, the properties of ASTM A216 steel should be improved. Therefore, in this article the rudder horn casting and accompanying specimens were cast moulded by arc furnace smelting, external refining, and modification treatment of the molten steel by lanthanum. The samples were first underwent normalizing treatment at 900 °C for 10 hours, then air cooled, followed by tempering treatment at 600 °C for 7 hours and samples were air cooled again. The mechanical properties and microstructures of the samples were measured. The crystallography relationships between lanthanum compounds formed in the molten steel and primary δ-Fe were analysed. The nucleation effect of lanthanum compounds as a heterogeneous nucleation core of primary δ-Fe were calculated and discussed based on two-dimensional mismatch theory. The results indicated that the strip MnS inclusions in ASTM A216 steel became granular rare earth compound inclusions due to La. The refined microstructures were obtained by a synergistic effect of the enhanced condensate depression and the nucleation rate of melt and La compounds as the heterogeneous nucleation caused by La.Da bi se zadovoljili standardi Međunarodnog udruženja klasifikacijskih zavoda (IACS) za lijevanje krmenog roga, potrebno je poboljšati svojstva čelika ASTM A216. Odljevci krmenog roda i prateći uzorci, nakon taljenja čelika u elektrolučnoj peći, rafiniranja i dodatka lantana, izrađeni su lijevanjem čelika u kalupe. Uzorci su prvo normalizirani zagrijavanjem 10 sati na 900 °C, ohlađeni na zraku, potom podvrgnuti popuštanju 7 sati na 600 °C i ponovno ohlađeni na zraku. Određena su mehanička svojstva uzoraka i proučena mikrostruktura. Analizirana je sličnost kristalne građe spojeva lantana nastalih u rastaljenom čeliku i δ-željeza. Izračunata je učinkovitost lantanovih spojeva kao podloge za heterogenu nukleaciju δ-željeza na temelju dvodimenzijskog nepodudaranja struktura. Dodatkom lantana vrpčasti uklopci MnS postaju zrnasti uklopci spoja rijetke zemlje. Finija mikrostruktura dobivena je sinergijskim djelovanjem povećane depresije kondenzata i brže nukleacije uz lantan

A structural determinant required for RNA editing

RNA editing by adenosine deaminases acting on RNAs (ADARs) can be both specific and non-specific, depending on the substrate. Specific editing of particular adenosines may depend on the overall sequence and structural context. However, the detailed mechanisms underlying these preferences are not fully understood. Here, we show that duplex structures mimicking an editing site in the Gabra3 pre-mRNA unexpectedly fail to support RNA editing at the Gabra3 I/M site, although phylogenetic analysis suggest an evolutionarily conserved duplex structure essential for efficient RNA editing. These unusual results led us to revisit the structural requirement for this editing by mutagenesis analysis. In vivo nuclear injection experiments of mutated editing substrates demonstrate that a non-conserved structure is a determinant for editing. This structure contains bulges either on the same or the strand opposing the edited adenosine. The position of these bulges and the distance to the edited base regulate editing. Moreover, elevated folding temperature can lead to a switch in RNA editing suggesting an RNA structural change. Our results indicate the importance of RNA tertiary structure in determining RNA editing

The Comparison of Distributed P2P Trust Models Based on Quantitative Parameters in the File Downloading Scenarios

Varied P2P trust models have been proposed recently; it is necessary to develop an effective method to evaluate these trust models to resolve the commonalities (guiding the newly generated trust models in theory) and individuality (assisting a decision maker in choosing an optimal trust model to implement in specific context) issues. A new method for analyzing and comparing P2P trust models based on hierarchical parameters quantization in the file downloading scenarios is proposed in this paper. Several parameters are extracted from the functional attributes and quality feature of trust relationship, as well as requirements from the specific network context and the evaluators. Several distributed P2P trust models are analyzed quantitatively with extracted parameters modeled into a hierarchical model. The fuzzy inferring method is applied to the hierarchical modeling of parameters to fuse the evaluated values of the candidate trust models, and then the relative optimal one is selected based on the sorted overall quantitative values. Finally, analyses and simulation are performed. The results show that the proposed method is reasonable and effective compared with the previous algorithms

Dynamic softening mechanism of 2 vol.% nano-sized SiC particle reinforced Al-12Si matrix composites during hot deformation

The hot deformation behavior of the 2 vol.% nano-SiCp/Al-12Si composites prepared by powder metallurgy is complicated due to the simultaneous presence of nano-sized SiC particles and micro-sized precipitated Si particles. In this paper, the isothermal heat compression test and the transmission electron microscope analysis technique were used to analyze the softening mechanism of the 2 vol.% nano-SiCp/Al-12Si composites based on Z parameters and deformation temperature, and the nucleation mechanism of dynamic recrystallization of the 2 vol.% nano-SiCp/Al-12Si composites was analyzed. The results showed that, when LnZ > 55.02, T ≤ 753 K, the cross slip of dislocation was the main softening mechanism; when LnZ < 55.76, T ≥ 733 K, the softening mechanism mainly includes the cross slip, climbing of dislocation, and untangling of three-dimensional dislocation network; when lnZ ≤ 53.65, T ≥ 773 K, the dynamic recovery and dynamic recrystallization were the main softening mechanism of the composites. The dynamic recrystallization nucleation mechanisms of the 2 vol.% nano-SiCp/Al-12Si composites include the sub-grain combination nucleation and grain boundaries bulging nucleation

Effects of Transition Element Additions on the Interfacial Interaction and Electronic Structure of Al(111)/6H-SiC(0001) Interface: A First-Principles Study

In this work, the effects of 20 transition element additions on the interfacial adhesion energy and electronic structure of Al(111)/6H-SiC(0001) interfaces have been studied by the first-principles method. For pristine Al(111)/6H-SiC(0001) interfaces, both Si-terminated and C-terminated interfaces have covalent bond characteristics. The C-terminated interface has higher binding energy, which is mainly due to the stronger covalent bond formed by the larger charge transfer between C and Al. The results show that the introduction of many transition elements, such as 3d transitional group Mn, Fe, Co, Ni, Cu, Zn and 4d transitional group Tc, Ru, Rh, Pd, Ag, can improve the interfacial adhesion energy of the Si-terminated Al(111)/6H-SiC(0001) interface. However, for the C-terminated Al(111)/6H-SiC(0001) interface, only the addition of Co element can improve the interfacial adhesion energy. Bader charge analysis shows that the increase of interfacial binding energy is mainly attributed to more charge transfer

Hot Deformation Behavior and Strain-Compensated Constitutive Equation of Nano-Sized SiC Particle-Reinforced Al-Si Matrix Composites

The hot deformation behavior of nano-SiCp/Al-Si composites was studied by isothermal compression tests at 470&ndash;530 &deg;C and strain rates of 0.01&ndash;5 s&minus;1. A strain-compensation constitutive model was developed with a Z parameter and an Arrhenius function, and its accuracy was verified by error analysis. The results show that the flow stress of the composites decreased with the increase in deformation temperature and the decrease in strain rate. The average activation energy for nano-SiC particle-reinforced Al-Si matrix composites was 277 kJ/mol, which was larger than the activation energy for self-diffusion of pure aluminum. The average relative error was calculated as 2.88%, indicating the strain-compensated constitutive equation could accurately predict the hot deformation behavior of nano-SiCp/Al-Si composites

Influence of titanium content on wear resistance of electrolytic low-titanium eutectic Al-Si piston alloys

The wear resistance of six kinds of the electrolytic low-titanium eutectic Al-Si piston alloys with various Ti content ranging from 0.00wt.% to 0.21wt.% has been studied. A new method of adding Ti is adopted in the electrolytic low-titanium aluminum alloy ingots. The electrolytic low-titanium eutectic Al-Si piston alloys are produced by remelting the electrolytic low-titanium aluminum alloy, crystal silicon, pure magnesium, Al-50%Cu and Al-10%Mn master alloy. The wear experiments are conducted using MM200 wear testing machine under lubricating condition. The results indicate that the better wear resistance and the less weight loss are achieved in the study for the eutectic Al-Si piston alloys with 0.08wt.%–0.12wt.% Ti content. The highest ultimate tensile strength of 135.94 MPa at 300℃ and HV141.70 hardness of the alloys are obtained at 0.12wt.% and 0.08wt.% Ti content, respectively. The wear mechanism of the eutectic Al-Si piston alloys under lubricating condition is abrasive wear

Calculating Study on Properties of Al (111)/6H-SiC (0001) Interfaces

The research elaborates on the mechanical properties at the Al (111)/6H-SiC (0001) interface based on the density functional theory. Because of the difference in atom category at the interface of 6H-SiC (0001), it takes the C-terminated interface and Si-terminated interface into account. As indicated by the gross energy computing results at the two interfaces, the C-terminated Al (111)/6H-SiC (0001) interface demonstrates a greater adhesion force than the Si-terminated counterpart. Throughout detailed analysis on the bonding mechanism, surface hybridization and charge transfer at the Al (111)/6H-SiC (0001) reaction interface, the research reveals its strong covalent characteristics. According to the comparative study on the ideal tensile strength and general stacking fault energy at varying cleavage surfaces, a conclusion can be fitly reached that the fracture at the Al (111)/6H-SiC (0001) interface is easily seen in Al-Al bonds in the Al matrix instead of C(Si)-Al bonds at the interface. Despite the greater adhesion energy of the C-Al bond than the Si-Al bond, Al-Al bonds close to the C-terminated Al (111)/6H-SiC (0001) interface easily fracture due to the low ideal tensile strength