Analytical and experimental study of investment casting with laser stereolithography models

This dissertation presents an analytical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography (SLA) patterns. Included in the consideration are the cracking temperature of the ceramic shell, the web link buckling temperature, and the glass transition temperature of the epoxy resin. The hypothesis is that shell cracking will occur when the cracking temperature is lower than the glass transition temperature and the web buckling temperature. An analytical and experimental study has been conducted, with the cross-sectional area, the span length of the web structure, and the shell thickness being the variables. It is found that the ceramic shell cracking and the internal web structure buckling are related to the cross-sectional area, the span length of the web structure, and the shell thickness. A finite element analysis (FEA) model is developed to simulate the burnout process in investment casting with an SLA webbed pattern. The numerical results show that the shell cracking in investment casting can be prevented by the buckling of epoxy webbed pattern in early stages of the burnout process. A strain gauge based experimental study validates the trend of the computational prediction from FEA of the burnout process in investment casting with SLA webbed epoxy patterns. The thermal insulation property of materials, additional expansion of adhesive and wax, and difficulty in temperature measurement contribute to the discrepancy of results. The FEA model is used to evaluate a new design of internal web structure for better yield of investment casting with SLA epoxy patterns. A hexagonal web structure has been analyzed in comparison with triangular and square web structures. The void ratio is increased to 0.89 for the hexagonal web structure from 0.79 for the triangular web structure and 0.83 for the square web structure. The induced stress on the ceramic shell is reduced by 32% and 22% compared with the triangular structure and square structure, respectively. In addition, the drainage of uncured liquid resin within the webbed SLA pattern is more efficient because of the larger interior angle and cross-sectional area of the hexagonal web geometry

Shear Moduli and Damping of Cohesive Soils under Earthquake Loads

To investigate the dynamic properties of soils under earthquake loading conditions, a series of cyclic triaxial compression tests vas carried out on undisturbed saturated samples of cohesive soils from Tianjin. It has come to the conclusion that variation of damping ratio, as well as shear modulus, with strain amplitude may be expressed by an empirical formula. Its normalized form can be shown by a family of curves or a band zone with shrunken ends. New empirical equations used for evaluating elastic or initial shear modulus G0 and maximum shear stress τmax have been suggested. For the two parameters, some comparisons between field and laboratory test values and between the results of cyclic and static triaxial compression tests under conditions of the same loading levels have been made

Transport properties of dense deuterium-tritium plasmas

Consistent descriptions of the equation of states, and information about transport coefficients of deuterium-tritium mixture are demonstrated through quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm$^{3}$ and a temperature of $10^{4}$ eV). Diffusion coefficients and viscosity are compared with one component plasma model in different regimes from the strong coupled to the kinetic one. Electronic and radiative transport coefficients, which are compared with models currently used in hydrodynamic simulations of inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is also discussed from the highly degenerate to the intermediate region.Comment: 4 pages, 3 figure

A Comprehensive Study on Knowledge Graph Embedding over Relational Patterns Based on Rule Learning

Knowledge Graph Embedding (KGE) has proven to be an effective approach to solving the Knowledge Graph Completion (KGC) task. Relational patterns which refer to relations with specific semantics exhibiting graph patterns are an important factor in the performance of KGE models. Though KGE models' capabilities are analyzed over different relational patterns in theory and a rough connection between better relational patterns modeling and better performance of KGC has been built, a comprehensive quantitative analysis on KGE models over relational patterns remains absent so it is uncertain how the theoretical support of KGE to a relational pattern contributes to the performance of triples associated to such a relational pattern. To address this challenge, we evaluate the performance of 7 KGE models over 4 common relational patterns on 2 benchmarks, then conduct an analysis in theory, entity frequency, and part-to-whole three aspects and get some counterintuitive conclusions. Finally, we introduce a training-free method Score-based Patterns Adaptation (SPA) to enhance KGE models' performance over various relational patterns. This approach is simple yet effective and can be applied to KGE models without additional training. Our experimental results demonstrate that our method generally enhances performance over specific relational patterns. Our source code is available from GitHub at https://github.com/zjukg/Comprehensive-Study-over-Relational-Patterns.Comment: This paper is accepted by ISWC 202

Topology of nonlinearly charged black hole chemistry via massive gravity

The classification of critical points of charged topological black holes (TBHs) in anti-de Sitter spacetime (AdS) under the Power Maxwell Invariant (PMI)-massive gravity is accomplished within the framework of black hole chemistry (BHC). Considering the grand canonical ensemble (GCE), we show that $d=4$ black hole have only one topological class, whereas $d\ge 5$ black holes belong to two different topology classes. Furthermore, the conventional critical point characterized by negative topological charge coincides with the maximum extreme point of temperature; and the novel critical point featuring opposite topological charge corresponds to the minimum extreme point of temperature. With increasing pressure, new phases emerge at the novel critical point while disappearing from the conventional one. Moreover, a atypical van der Waals (vdW) behavior is found in $d\ge 6$ dimensions, and the anomaly disappears at the traditional critical point. In the limit of nonlinearity parameter $s\to1$, different topology classes are only obtained in the GCE and they may not exist within the canonical ensemble. With the absence of electric potential $\Phi$, the neutral TBHs share the same topological classification results as the charged TBHs in the GCE of Maxwell-massive gravity.Comment: 16pages,22 figure

Joule-Thomson expansion of charged dilatonic black holes

Based on the Einstein-Maxwell theory, the Joule-Thomson (J-T) expansion of charged dilatonic black holes (the solutions are neither flat nor AdS) in $(n+1)$-dimensional spacetime is studied herein. To this end, we analyze the effects of the dimension $n$ and dilaton field $\alpha$ on J-T expansion. An explicit expression for the J-T coefficient is derived, and consequently, a negative heat capacity is found to lead to a cooling process. In contrast to its effect on the dimension, the inversion curve decreases with charge $Q$ at low pressures, whereas the opposite effect is observed at high pressures. We can observe that with an increase in the dimension $n$ or parameter $\alpha$, both the pressure cut-off point and the minimum inversion temperature $T_{min}$ change. Moreover, we analyze the ratio $T_{min}/T_{c}$ numerically and discover that the ratio is independent of charge; however, it depends on the dilaton field and dimension: for $n=3$ and $\alpha=0$, the ratio is 1/2. The dilaton field is found to enhance the ratio. In addition, we identify the cooling-heating regions by investigating the inversion and isenthalpic curves, and the behavior of the minimum inversion mass $M_{min}$ indicates that this cooling-heating transition may not occur under certain special conditions