Degree Of Deformation Research Articles

Determination of Limiting Deformations at Testing Cylindrical Samples for Tension

This paper proposes a method for calculating limiting deformations under conditions of localized deformation during tensile testing. The method for calculating limiting deformations was used to construct plasticity diagrams under conditions of strain localization under uniaxial tension.
 The plasticity diagram is one of the material functions that forms the technological map of the material. The plasticity diagram displays the properties of a material depending on the degree of deformation and the stress state scheme.
 According to the studies carried out in this work, it was established that the critical increase in plasticity with increasing stress state indicator is explained by the influence of three factors: the strain gradient, the history of deformation and the third invariant of the stress tensor.
 The obtained dependencies make it possible to construct plasticity diagrams for materials whose destruction is preceded by localized deformation in the form of a "neck".
 This work establishes the quantitative influence of these three factors on the magnitude of the limiting deformations of a sample stretched to the point of failure.
 Application plasticity diagrams constructed using the proposed methods for cold plastic deformation processes, depending on the type of deformation path and the features of metal rheology, clarifies the value of the used plasticity resource of the metal, which allows to reduce the number of defective products for processes whose modes are calculated according to limit deformations.

Activating multiple slip systems in the laves phase improves the high-temperature strength and elastic coordination of (TiZr)65-XNb15Mo20CrX alloy

Introducing Laves phase into refractory multi-principal elements alloys (RMPEAs) is a new exploration direction to improve the alloy strength. In this work, we have prepared a series of (TiZr)65-XNb15Mo20CrX (x = 5,10,15,20) multi-principal elements alloys, by the addition of Cr to introduce the Laves phase for excellent high-temperature performance. The microstructure, phase constituents, and mechanical properties of the refractory high-entropy alloy were studied in the present work. Most of these alloys exhibited typical dendrite morphology, except for the alloy Cr5. Excessive Cr results in the formation of TiZr-enriched zones. In addition, twins can appear in as-cast alloys as a result of a significant lattice mismatch between the matrix and the Laves phase, which is caused by the rapid cooling process during melting. All alloys demonstrate remarkable strength when exposed to high temperatures, with compressive yields surpassing 552 MPa, peaking at 712 MPa at 800 °C, and compressive strains exceeding 30%. Benefiting from the Laves phase, the alloys do not show significant softening, making it possible for this alloy to work stably at 800 °C. Analyses of high-temperature specimens under different degrees of deformation reveal that small-sized Laves phases containing nano-twins precipitate in the matrix. The small-sized Laves phases and nano-twins restrict the movement of dislocations, leading to a large amount of dislocation accumulation, which improves the strength and plasticity of the alloy. Therefore, the current work on designing novel alloys provides new ideas for developing RMPEAs with synergistic strength and plasticity.

Computer-Assisted Surgery in Total Knee Arthroplasty: Our Experience.

Total knee arthroplasty (TKA) is a reliable orthopedic procedure for knee osteoarthritis with long-term success rates of 90% after 15years. Computer-assisted surgery (CAS) has been developed to improve the accuracy of the alignment and orientation of the components in TKA. A prospective study involving 103 subjects who underwent CAS-TKA was conducted over a 3-year period. Subjects were assessed for pre- and post-operative varus and valgus deformity, BMI, comorbidities, and Knee Society Score (KSS). Outcome measures of post-operative KSS, post-operative alignment, and hospital stay were examined by Spearman correlation coefficients. Categorical outcomes of complication and secondary procedures were compared by chi-squared test and odds ratio. The study considered 103 TKA patients with a mean ± SD age of 63.7 ± 8.4years (33-88years). Unilateral knee replacement was performed on 56 patients (54.3%) and remaining 47 (45.6%) had simultaneous bilateral TKA. Forty (34.8%) patients were obese, and severe pre-operative deformity (> 15°) was observed in 47 (31.3%) patients. Mean coronal alignment of the knee joint was 91.33° (SD: 90.69° valgus-88.92° varus). The mean post-operative KSS noted in obese and non-obese subjects were 93.43 (84-98) and 94.76 (85-98) respectively. Post-operative KSS for knees with severe deformity was 94.08 (80-98), while it was 95.76 (83-98) in those with mild to moderate deformities. The study confirms that navigation in CAS-TKA consistently achieved coronal alignment of the knee joint within ± 3°, irrespective of the patient BMI and degree of deformity.

Effect of Deformation Degree on Microstructure and Properties of Ni-Based Alloy Forgings

The primary objective of this paper is to investigate the influence of deformation degree on the microstructure and properties of a Ni-based superalloy. An upsetting experiment was conducted using a free-forging hammer to achieve a deformation degree ranging from 60% to 80%. The impact of the forging deformation degree on the hardness and high-temperature erosion performance was evaluated using the Rockwell hardness tester (HRC) and high-temperature erosion tester, respectively. The experimental results indicate that as the deformation degree increased, the hardness of the forged material progressively increased while the rate of high-temperature erosion gradually decreased. In order to comprehensively study the mechanism behind the variations in forging performance, optical microscopy (OM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM) were employed. The findings reveal that as the deformation degree increased, the presence of small-angle grain boundaries and an increase in grain boundary area contributed to enhanced hardness in the alloy forgings. Furthermore, it was discovered that grain boundaries with twin orientation promoted dynamic recrystallization during deformation, specifically through a discontinuous dynamic recrystallization mechanism. Additionally, the precipitated γ′ phase in the alloy exhibited particle sizes ranging from 40 to 100 nm. This particle size range resulted in a higher critical shear stress value and a more pronounced strengthening effect on the alloy.

Alignment is only part of the equation: High variability in soft tissue distractibility in the varus knee undergoing primary TKA.

The purpose of this study is to evaluate the in vivo medial and lateral joint laxities across various total knee arthroplasty (TKA) alignment categories correlated to (1) hip-knee-ankle angle, (2) proximal tibial angleand (3) distal femoral angle in a consecutive group of patients undergoing robotic-assisted TKA. Using ligament tensions acquired during 805 robotic-assisted TKA with a dynamic ligament tensor under a load of 70-90 N, the relationship between medial and lateral collateral ligament laxity and overall limb alignment was established. Only knees with neutral or mechanical varus alignment were included and divided into fivegroups: neutral (0°-3°), varus 3°-5°, varus 6°-9°, varus 10°-13° and varus ≥14°. Groups were further subdivided by the intraoperative medial proximal tibial angle (MPTA) and lateral distal femoral angle (LDFA). The distraction of the medial and lateral sides was compared across the various alignments using an analysis of variance. The ability to distract the medial collateral ligament in extension and flexion was proportional to the degree of varus deformity, increasing from 4.0 ± 2.3 mm in the neutral group to 8.7 ± 3.2 mm in the varus ≥14° group (p < 0.0001). On the lateral side, the distraction of the lateral collateral ligament decreased in both extension (2.2 ± 2.4 vs. 1.2 ± 2.7, p < 0.0001) and flexion (2.8 ± 2.8 to 1.7 ± 3.0, p < 0.0001) with increasing native varus deformity. MPTA and LDFA had similar effects, where increasing MPTA varus and LDFA valgus increased medial distractibility in extension and flexion. There was significant variability of the stretch of the ligaments within and across all alignment categories, in which the standard deviation of the groups ranged from 2.0 to 3.0 mm. This study demonstrates increased medial ligament distractibility with increasing varus deformity. However, there was significant variability in ligamentous laxity within various limb alignment categories suggesting the anatomy and soft tissue identity of the knee is complex and highly variable. TKAs seeking to be more anatomic will not only need to restore alignment but also native soft tissue tensions. Level III, prognostic.

Metallographic study of non-ferrous metal products from the Maray 1 site of the Baitovo Cul-ture in the Lower Ishim River region

The article examines non-ferrous metal products from the Baitovo Culture materials of the Early Iron Age hillfort of Marai 1. This settlement is located in the forest-steppe of the Ishim River region of Western Siberia. The upper building hori-zon marks the settlement of the Baitovo Culture dating to the 4th–2nd centuries BC. Metallographic analysis of 28 items was carried out using the Axio Observer D1m microscope (Zeiss). As a result, eight technological schemes characteristic for the metalworking activities of the Baitovo population have been identified. The study shows that prevailing were smithing tech-nologies in different temperature regimes for the production of non-ferrous metal objects (16 specimens, 57.2 %). The pref-erence was given to hot forging in the red-heat regime at 600–800°C (7 specimens, 25 %), cold forging with annealing (5 specimens, 17.8 %), as well as incomplete hot forging at 300–500°C (3 specimens, 10.7 %). Casting without further refine-ment was recorded in the microstructures of arrowheads, ingots and splashes (9 specimens, 14.2 %). Casting, followed by a slight degree of deformation (20–30 %), was noted in three cases. This scheme correlates with the metalworking traditions of the Itkul and Krasnoozerskaya Cultures, and it was dominant on the territory of the Tobol-Ishim region during the Early Iron Age. Such a low percentage of items related to it could be explained by the absence in Marai 1 of large items cast in moulds needing further refinement (knives, celts, etc.). A microstructural study confirmed the use of pure oxidized copper by the craftsmen of the Baitovo Culture, with characteristic inclusions of Cu–Cu2O eutectic, associated with the Ural production centres. Arrowheads and an ingot made of pure oxidized copper were probably a direct import from the territory of the Itkul Culture. Low-alloy tin and arsenic bronzes, coming from the metal production centres of Kazakhstan and Altai, were also used to the same extent for production of some tools and jewellery. The correlation between the type of product, composition of raw materials and technology of its manufacture has been revealed, which is most clearly manifested in arrowheads and awls. The use of high temperatures and significant degrees of compression (80–90 %) has been recorded in a number of cases, resulting in the appearance of rejects. Cracks of hot brittleness, as well as of cold brittleness, occurred in the process of technological cycle, carried out with an excess of the tensile strength of the metal.

An insight into the mechanical behavior and failure mechanisms of T-stiffened composite structures with through-interface debonding defects

A robust 3D finite element model framework was established to capture the mechanical behavior and failure mechanisms of intact and through-interface debonding T-stiffened composite structures based on the progressive damage model and the cohesive zone model. Meanwhile, specimens with and without interface debonding defects were fabricated to validate the reliability and robustness of the proposed modeling framework. Finally, a parametric study was conducted on the types of interfacial debonding to further explore the effect on the buckling load, delamination initiation load, and ultimate load-carrying capacity of the composite stiffened structure. The results indicate that the load-carrying capacity of both single interface defects and double interface defects decreases gradually with increasing defect length and converges to a constant value. The reductions were 28.31% and 47.68%, respectively, compared to the intact structure. Interestingly, interfacial debonding has the most significant effect on the ultimate load at the 1/4 position. Moreover, interface debonding defects not only severely weaken the ultimate load-carrying capacity of the structure but also significantly alter the post-buckling path and failure mechanism, resulting in distinct degrees of deformation and damage morphology.

Outcomes of Pediatric Proximal Phalanx Base Fractures.

Extra-articular juxtaphyseal fractures of the proximal phalanx are among the most common finger fractures in children. Immobilization of the digit for 3 to 4 weeks after reduction of the fracture is the current standard of care. The purpose of this retrospective study was to evaluate outcomes after intervention among pediatric proximal phalanx base fractures and establish radiographic criteria to guide management. A multi-institutional retrospective review of skeletally immature patients treated for proximal phalanx juxtaphyseal fractures between 2002 and 2019 was conducted. Variables collected included Salter-Harris classification; initial, postreduction, early follow-up, and final angulation and displacement on the posterior-anterior and lateral radiographs; clinical rotational deformity at final follow-up; and method of treatment. Exclusion criteria included less than 3 weeks of follow-up; Salter-Harris III, IV, and V fractures; inadequate medical record details; and missing radiographs. Six hundred thirty-four fractures meeting the inclusion criteria were categorized into no reduction, closed reduction (CR), and surgical (OP) groups. Only CR and OP groups saw large decreases in angulation by 11.8° CR (95% confidence interval, 10.1 to 13.6) and 19.0° OP (95% confidence interval, 8.7 to 29.3). Closed reduction patients had a mean coronal angulation value of 6.1° at post-reduction, which was maintained with immobilization to 5.8° at final follow-up. At final follow-up, scissoring was noted, three in the no reduction and three in the CR group for an overall 0.93% rotational malalignment rate. Extra-articular proximal phalanx juxtaphyseal fractures rarely require surgical management and can typically be treated with or without CR, based on the degree of deformity, in the emergency department or clinical setting. Low rates of documented sequelae after nonsurgical management were seen in this cohort, allowing for establishment of treatment parameters that can result in clinically insignificant angular and rotational deformity. Therapeutic IV.

Effect of nanosecond pulse laser power on welding interface and mechanical properties of AZ31B Mg/6061 Al

AZ31B magnesium alloy and 6061 aluminum alloy of 0.2 mm thickness were joined by nanosecond pulsed laser welding technology, and the effects of nanosecond pulsed laser power on the formation of weld seam, interface microstructure and mechanical properties were investigated, and numerical simulation of the temperature field during the welding process was carried out. The results show that when the laser power is 50 W, more defects such as cracks, pores and sags appeared in the joints due to the high heat input, and these defects resulted in a smaller effective joint area between the metals, which is very unfavorable to the strength of the joints. As the laser power decreases, at a laser power of 25 W, fewer defects are exhibited and the effective joint area becomes larger. As the laser power continues to decrease, the low heat input makes metal melting and joining very difficult. At low laser power, the Mg element intrudes backwards into the aluminum, causing the joint boundary interface to take on a reverse “V” shape. According to the results of the tensile shear experiments, the maximum tensile force of the joint was the highest at a laser power of 25 W, which reached 76.5 N. In addition, it was observed that the effective joint area, the number of oxides and their inclusions, and the degree of angular deformation had a very important effect on the mechanical properties of the joints. The results of temperature field numerical simulation experiments show that the heat is accumulated from outside to inside during the laser scanning process, and whether the temperature in the center of the molten pool reaches the melting point of the alloy can be used as an important basis for analyzing the degree of welding.

Dilation and energy evolution mechanisms of sandstone under true-triaxial mining unloading conditions

The study of sandstone dilation characteristics under actual mining and excavation conditions promotes the safe and efficient development of underground engineering. Accordingly, this study employs true-triaxial testing to reveal the influence of intermediate principal stress and unloading action in the minimum principal stress directions on rock dilation. In the stress–strain analysis, with increasing intermediate principal stress, the maximum compression of the sandstone volume in the loading and unloading tests increases, while the onset of dilation is delayed under loading conditions and initially delayed and then accelerated under unloading conditions. The energy storage limit of sandstone under the unloading test tends to decrease with increasing intermediate principal stress, contrary to the results of the loading test, and the characteristic point at which the percentage of dissipative energy is greater than that of elastic energy occurs earlier. The energy of sandstone in the unloading test in the intermediate principal stress direction was smaller than that in the minimum principal stress direction, while the loading test showed the opposite trend. Combining these two analyses can elucidate the restraining effect and tensile stress effect of the intermediate principal stress, as well as the weakening and strengthening effects of the unloading action on the two effects. By further combining the average elastic energy and dissipative energy conversion rate under different test conditions, the weakening effect was manifested by shortening the compressive deformation course, and the strengthening effect was manifested by developing the degree of plastic expansion deformation. This study provides important guidance for deep mining projects.

Failure Behavior and Fracture Evolution Mechanism of Coal with Fissures around Holes.

The fracture of coal is the main channel of gas flow and an important factor affecting the stability and efficiency of gas drainage boreholes. The coal structure, the development of hole cracks, and the degree of deformation are different. It affects the strength and mechanical deformation characteristics of coal to a great extent. In order to investigate the law of fracture evolution around the borehole of fractured coal, uniaxial and triaxial compression tests of raw coal samples have been carried out. The stress field evolution characteristics of fractured coal under compression were analyzed by Particle Flow Code (PFC2D). The strength, deformation, and fracture evolution behavior of fractured coal around boreholes under different confining pressures were studied. The results show that the compressive strength and fracture morphology evolution characteristics of coal around the hole are obviously related to the confining pressure and fracture occurrence of raw coal. The borehole structure itself has an important influence on the distribution location of the shear failure zone of the fracture around the hole, and its influence degree increases with the decrease of borehole confining pressure. During the deformation of coal with cracks around the hole, the initiation, propagation, and union behavior of cracks are related to the crack angle β. The cracks with β 0 and 180° are most easily closed during compression and the cracks with β 90° have little effect on the crack propagation zone. When the crack angle β is 45°, it is most easy to sprout and expand at the end; when the coal is compressed to the ultimate strength, the increase rate of the tensile crack increases, and the polymerization and combination behavior of the crack is more obvious. The evolution cloud map of the stress field can better reflect the evolution characteristics of fracture development, expansion, and fracture in the process of coal loading. Studying the failure behavior and fracture evolution mechanism of the coal around the hole can better predict and control the gas migration and extraction effect, which is of great significance to prevent the occurrence of gas accidents.

Modeling and improvement for the thermal stability of ring-shaped workpieces with shape boundary constraints

Ring-shaped workpieces are commonly utilized in high-precision measuring instruments, and their thermal deformation affects the instruments’ measuring accuracy. A novel method for establishing the thermal deformation model of ring-shaped workpieces is proposed in this article. The mechanism of thermal deformation caused by shape boundaries is investigated using the principle of molecular dynamics. A mathematical model between deformation degree and height, diameter ratio, or temperature is created using a large-scale atomic/molecular massively parallel simulator. The established model is verified by measuring the thermal deformation of ring-shaped workpieces. The model is used to optimize laser collimation systems, and stability experiments for laser collimation systems in different sizes are performed. The stability of optimized systems can be improved by 50%, 50%, and 48% with temperature increases of 10 °C, 20 °C, and 30 °C, respectively. The experimental results indicate the obtained model can be utilized to improve the stability of instruments.

Valgus malalignment causes increased forces on a medial collateral ligament reconstruction under dynamic valgus loading: Abiomechanical study.

To investigate the forces on a medial collateral ligament (MCL) reconstruction (MCLR) relative to the valgus alignment of the knee. Eight fresh-frozen human cadaveric knees were subjected to dynamic valgus loading at 400 N using a custom-made kinematics rig. After resection of the superficial medial collateral ligament, a single-bundle MCLR with a hamstring tendon autograft was performed. A medial opening wedge distal femoral osteotomy was performed and fixed with an external fixator to gradually adjust the alignment in 5°increments from 0° to 10° valgus. For each degree of valgus deformity, the resulting forces acting on the MCLR were measured through a force sensor and captured in 15° increments from 0° to 60° of knee flexion. Irrespective of the degree of knee flexion, increasing valgus malalignment resulted in significantly increased forces acting on the MCLR compared to neutral alignment (p < 0.05). Dynamic loading at 5° valgus resulted in increased forces on the MCLR at all flexion angles ranging between 16.2 Nand 18.5 N (p < 0.05 from 0° to 30°; p < 0.01 from 45° to 60°). A 10° valgus malalignment further increased the forces on the MCLR at all flexion angles ranging between 29.4 Nand 40.0 N (p < 0.01 from 0° to 45°, p < 0.05 at 60°). Valgus malalignment of the knee caused increased forces acting on the reconstructed MCL. In cases of chronic medial instabilities accompanied by a valgus deformity ≥ 5°, a realigning osteotomy should be considered concomitantly to the MCLR to protect the graft and potentially reduce graft failures. Level III.

Bending deformation modulation of the optoelectronic properties of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, O): a first-principles study.

A first-principles approach based on density functional theory was used to explore the effect of bending deformation on the electrical structure of molybdenum ditelluride doped with nonmetallic atoms X (X = B, C, N, and O). The study included alternate doping of nonmetallic atoms, as well as a comparison of the effects of intrinsic bending deformation and nonmetallic doping deformation. The results demonstrate that boron atom doping raises the Fermi energy level. Examining the energy band structure indicates that the intrinsic molybdenum ditelluride is a direct band gap semiconductor, which is transformed from a direct band gap to an indirect band gap after doping. We selected boron-doped systems for bending deformation and compared them with the intrinsic systems. With increasing deformation, all systems start to shift from semiconductor to metal. When the deformation reaches 8°, the energy levels fill and the electron energy increases. The intrinsically bent systems transition from direct band gap to indirect band gap and eventually to metal. The indirect band gap semiconductor-to-metal transition process occurs after the bending deformation of the boron-doped atoms. The analytical results show that the absorption and reflection peaks of the molybdenum ditelluride system are blue-shifted after the bending deformation of the boron-doped atoms. Under fundamental principles, this research depends on the density functional theory framework (DFT) using the CASTEP module in the Materials-Studio software. The plane-wave pseudopotential approach with modified gradient approximation and the Perdew-Burke-Ernzerhof (PBE) generalized function is used for structure optimization and total energy calculations of the X-doped (X = B, C, N, O) MoTe2 system at different shape variables. Geometry optimization of the 27-atom superlattice MoTe2 was carried out, followed by alternative doping of tellurium atoms in the molybdenum ditelluride with B, C, N, and O. In this paper, the intrinsic bending deformation and B-doping of molybdenum ditelluride were selected for deformation analysis. Intrinsic bending deformations and boron-doped molybdenum ditelluride with bending angles ranging from 2° to 8° were employed for deformation investigation. In Fig.1, pink is used to represent doped B atoms, orange is used to describe Te atoms, and green is used to represent Mo atoms. For the degree of deformation of molybdenum ditelluride, in this paper, it is expressed by the bending angle, i.e., the angle of the plane of molybdenum ditelluride after bending and deformation of a single layer of molybdenum ditelluride concerning the angle of the plane folded for the deformed plane. How to do it: For ease of presentation, the atomic chains are set to different colors. The purple part on both sides of the figure is bent and deformed, 3-5 atoms are fixed appropriately, and the middle part is deformed. On this basis, the bending deformation of intrinsically doped and boron-doped MoTe2 is comparatively analyzed. The effect of boron-doped atoms on the structure of MoTe2 is systematically investigated to study its structural stability and electronic structure. Fig.1 a1 and a2 The main and side views of intrinsic MoTe2; b1 and (b2) the main and side views of MoTe2 doped with boron atoms bent by 8°.

Evaluation of cracking risk of 80MnSi8-6 nanobainitic steel during hot forging in the range of lower temperature limits

Abstract Nanobainitic steels exhibit an exceptional combination of high strength, good plasticity, impact toughness, and wear resistance. They are suitable for the production of large mass components through the open-die forging process. Subsequently, the forgings are air-cooled. An obstacle of this method is the extended time required for the large forgings to undergo a bainitic transformation, making the industrial implementation of this process economically unjustifiable. Nevertheless, nanobainitic steels also allow for the open-die forging of small batches of structural elements with high property requirements. A technological limitation lies in the necessity of performing a series of operations, leading to a prolonged processing time dependent on the shape of the product and the degree of deformation. Therefore, inter-operational reheating is often necessary, incurring costs and time consumption. This is particularly relevant to forgings with a mass ranging from a few to several dozen kilograms, which, due to their low thermal capacity, rapidly dissipate heat to the surroundings and tools. Designing an economical process with a limited number of reheating cycles requires advanced knowledge of material behavior under thermo-mechanical deformation parameters, including boundary conditions where a significant decrease in plasticity occurs and the risk of crack initiation. To obtain this information, a comprehensive analysis of the influence of thermo-mechanical parameters applied during the deformation of nanobainitic steel at relatively low temperatures on the flow characteristics and crack formation was conducted. To achieve this goal, the Digital Image Correlation method, the finite element method modeling considering damage criteria, and the macrostructural evaluation of deformed specimens were employed.

Deformation behavior of SmCo compounds via amorphization and recrystallization

In recent years, nanocrystalline magnets based on the critical single domain size theory have received increasing attention. However, nanocrystalline magnets are difficult to enhance the remanent magnetization by forming textures with conventional magnetic field orientation. Texturing of nanocrystalline magnets is usually done using the hot pressing and hot deformation technique, but there are some difficulties in applying this technique to form texture in SmCo systems. To discover and solve the difficulties of obtaining texturized nanocrystalline SmCo-based magnets during the deformation process, samarium cobalt magnets with different degrees of deformation were first experimentally prepared by low strain rate hot deformation method. Then, molecular dynamics simulations were utilized to study the microstructural changes and the multi-phase formation process during hot deformation. The process of deformation together with the reason why it is difficult to form textures in SmCo systems by low-temperature hot deformation is discussed, and the strain energy densities of SmCo multiphase in multiple directions were calculated, which gives a feasible method to form low-temperature hot deformation textures in SmCo systems experimentally.

BGS Distribution Deformation in BOTDR Induced by Self-Phase Modulation

We report the numerical and experimental studies of the two-dimensional Brillouin gain spectrum (BGS) distribution deformation induced by the self-phase modulation in the Brillouin optical time domain reflectometry (BOTDR) with a 20.6 km sensing distance. The BGS distribution deformation is investigated by analyzing the evolution of the point spread function along the fiber in the two-dimensional model of the BOTDR. In the simulation and experimental results, the specific deformation degree of the BGS distribution induced by the self-phase modulation is related to the pump pulse profile, pump pulse peak power, BGS demodulation method, and detected scattered light component. By comprehensively analyzing the evolution of the point spread function induced by the self-phase modulation and using the image deconvolution, a typical BOTDR sensor with a 25 ns pump pulse reaches the 20 cm spatial resolution over the 20.6 km sensing fiber.

Cellulose-Callose Hydrogels: Computational Exploration of Their Nanostructure and Mechanical Properties.

Polysaccharides play a crucial role in virtually all living systems. They also represent the biocompatible and fully sustainable component of a variety of nanoparticles, which are of increasing interest in biomedicine, food processing, cosmetics, and structural reinforcement of polymeric materials. The computational modeling of complex polysaccharide phases will assist in understanding the properties and behavior of all these systems. In this paper, structural, bonding, and mechanical properties of 10 wt % cellulose-callose hydrogels (β-glucans coexisting in plant cell walls) were investigated by atomistic simulations. Systems of this kind have recently been introduced in experiments revealing unexpected interactions between the polysaccharides. Starting from initial configurations inspired by X-ray diffraction data, atomistic models made of ∼1.6 × 106 atoms provide a qualitatively consistent view of these hydrogels, displaying stability, homogeneity, connectivity, and elastic properties beyond those of a liquid suspension. The simulation shows that the relatively homogeneous distribution of saccharide nanofibers and chains in water is not due to the solubility of cellulose and callose, but to the formation of a number of cross-links among the various sample components. The broad distribution of strength and elasticity among the links implies a degree of anharmonicity and irreversible deformation already evident at low external load. Besides the qualitative agreement with experimental observations, the simulation results display also quantitative disagreements in the estimation of elastic coefficients, such as the Young's modulus, that require further investigation. Complementary simulations of dense cellulose-callose mixtures (no hydrogels) highlight the role of callose in smoothing the contact surface of different nanofibers forming larger bundles. Cellulose-callose structures in these systems displayed an enhanced water uptake and delayed dye release when compared to cellulose alone, highlighting potential new applications as drug delivery scaffolds. The simulation trajectories provide a tuning and testing ground for the development of coarse-grained models that are required for the large scale investigation of mechanical properties of cellulose and callose mixtures in a watery environment.

Morphological and quantitative study of the inferior alveolar nerve canal in hemifacial microsomia.

This study aimed to probe into the anatomic course of inferior alveolar nerve canal (IANC) in hemifacial microsomia (HFM) on a large scale, morphological observations and further quantitative study were performed. Patients were classified by Pruzansky-Kaban classification. The anatomic course of IANC was analyzed morphologically with three-dimensional (3D) imaging software among 248 patients. Seven distances between fixed landmarks on both sides were measured for 236 patients. The differences between affected and unaffected sides were compared. Significant differences were found in the entrance (P < 0.001), route (P < 0.001), and exit (P < 0.05) of IANC in type IIb and III HFM. The higher the degree of mandibular deformity was, the higher the incidence of IANC variation was (P < 0.05). The distances in the horizontal aspect of IANC including from mandibular foramen to mental foramen (P < 0.05) and from mental foramen to gonion (P < 0.05) were significantly shorter on the affected side. Abnormalities of the anatomical course of IANC exist in patients with Pruzansky-Kaban type IIb and type III HFM. The reduction of IANC on the affected side in the horizontal distance is more obvious. Three-dimensional imaging assessment is recommended before surgery.

Local Instability and Deformation Control of Steel Roof of Factory Building in a Smart City

Abstract The traditional control methods of instability and deformation of steel structure neglect the analysis of its natural vibration characteristics, which lead to the poor effect of hysteretic vibration of steel structure nodes, and the stability optimization of steel structure is not ideal. Therefore, a new method to control the local instability and deformation of the steel roof is proposed. According to the steel structure composition of the upper door rigid frame and the connection mode of the frame beam and column, the roof steel structure characteristics of the workshop are analyzed. Multi-order natural frequency method is used to obtain the cumulative modal mass contribution rate of steel structure and analyze the natural vibration characteristics of steel structure. Based on the characteristics of natural vibration and element transfer matrix, the local instability control method of roof steel structure is designed. Simulation of strong vibration, using space analysis of tall-building with wall-elements (SATWE) software analysis of strong vibration under elastic load state, to obtain the external deformation of steel structure, under simulation of vibration deformation control model. Taking a chemical plant as an example, a finite element model was established to simulate the vibration wave, and the numerical simulation results of plastic deformation resistance of steel structure were analyzed. The experimental results show that the proposed method can effectively enhance the stability of steel structure and reduce its deformation degree.