Factors affecting the stability of nitrate molten salts at a high temperature

熔盐是太阳能热利用领域重要的储热材料之一，熔盐使用温度上限越高，储热量就越大，能量传递效率越高。为了提高熔盐使用温度上限，以Solar Salt与HITEC两种常用硝酸熔盐为对象，将实验和量子化学计算相结合研究了影响高温稳定性的因素。首先通过静态熔融法制备了Solar Salt与HITEC熔盐，并通过DSC-TG曲线分析了二者的高温稳定性，通过XPS分析了分解产物，通过计算软件模拟了硝酸盐分解为亚硝酸盐的过程，采用的是B3LYP泛函和6-31+G^*基组。最后从反应机理的角度对影响二者高温稳定性的因素进行了讨论。研究结果表明，当熔盐升温至600℃时，Solar Salt和HITEC的失重分别为2%和1%，并且亚硝酸盐没有进一步分解为金属氧化物或反应进度较小，K⁺和Na⁺的半径不一致，二者比例的不同是造成这两种熔盐稳定性差异的因素之一。同时，由反应物浓度不同导致化学平衡的移动，这也使HITEC较难分解。     

Multiphysics design and analysis of an impeller-type superfine grinding turbulence mill driven by a high-speed permanent magnet machine

Journal of Mechanical Science and Technology - Superfine grinding technology is widely used in various industries, such as food, medicine and chemistry. Traditional superfine grinding methods have...     

Suitable rolling resistance model for quasi-static shear tests of non-spherical particles via discrete element method

Rolling resistance is a main consideration in quasi-static shear test simulations of particles via the discrete element method. However, not all rolling resistance models can satisfy the required objectivity and rate independence. A suitable model for spherical particles has been selected from five models in our previous works. In the current study, this model is combined with four normal and tangential contact models to confirm its applicability. After confirmation, the model is generalized to simulate direct shear tests on non-spherical particles. The stress–strain and dilatancy curves are rate-independent, and the relative rolling velocity between particles is objective. Furthermore, objectivity and rate independence for arbitrarily shaped particles are unchanged when normal stresses, volume fractions, or normal and tangential contact models are changed. Simulation results are also consistent with other experiment findings. For comparison, results are calculated for two other rolling resistance models; the shear curve at a single speed is consistent with the experiment, which has three stages: elastoplastic increasing, yielding, and keeping. However, the stress–strain curves at different shear rates do not coincide, which means that the models conflict with the rate independence of quasi-static granular systems. The virtues and defects of the five rolling resistance models are discussed from the perspectives of objectivity and rate independence. These two properties provide criteria for determining the appropriateness of a model, which has been rarely discussed in former studies.     

Microstructure and mechanical properties of Ti–C–TiN-reinforced Ni204-based laser-cladding composite coating

In situ Ti(C, N), ring phase, and multi-phase enhanced Ni204-based alloy coating were prepared by adding various Ti/C/TiN ratios particles. The effects of the reinforcement phase on the microstructure, microhardness, tribological property, and microstructure characteristics at the interface between the coating and substrate were investigated. The results show that the coatings with a 5:1 mass fraction ratio of TiN/C exhibits the highest microhardness, which is 3.78 times higher than that of the original Ni204 coating. While, the coating with 21:7:2 mass fraction ratio of TiN/Ti/C exhibits the lowest friction coefficient, which is 4.44 times smaller than that of the original Ni204 coating. The addition of Ti and C particles promotes the precipitation of ring phase and carbides, reduces ceramic agglomeration, alleviates the floating of ceramic particles, and improves the bonding strength of reinforcement phases. Owing to the good mutual solubility among Fe, Ni, and, Cr elements, the diffusion happened at the interface between the coating and substrate.     

倾斜摄影结合BIM技术辅助设计施工数字孪生的应用与研究

研究高速公路施工项目的 数字孪生技术,利用无人机航测采集物理世界的地理数据信息,形成地勘模型及图纸,高效完成设计与分析,应用BIM技术完成实体模型创建及深化设计,保证了项目的 施工进度及物料采购准确;在施工阶段模型指导现场施工分析,在运维阶段可利用模型定位分析工程运行情况.     

Systems Approach to Pathogenic Mechanism of Type 2 Diabetes and Drug Discovery Design Based on Deep Learning and Drug Design Specifications

In this study, we proposed a systems biology approach to investigate the pathogenic mechanism for identifying significant biomarkers as drug targets and a systematic drug discovery strategy to design a potential multiple-molecule targeting drug for type 2 diabetes (T2D) treatment. We first integrated databases to construct the genome-wide genetic and epigenetic networks (GWGENs), which consist of protein–protein interaction networks (PPINs) and gene regulatory networks (GRNs) for T2D and non-T2D (health), respectively. Second, the relevant “real GWGENs” are identified by system identification and system order detection methods performed on the T2D and non-T2D RNA-seq data. To simplify network analysis, principal network projection (PNP) was thereby exploited to extract core GWGENs from real GWGENs. Then, with the help of KEGG pathway annotation, core signaling pathways were constructed to identify significant biomarkers. Furthermore, in order to discover potential drugs for the selected pathogenic biomarkers (i.e., drug targets) from the core signaling pathways, not only did we train a deep neural network (DNN)-based drug–target interaction (DTI) model to predict candidate drug’s binding with the identified biomarkers but also considered a set of design specifications, including drug regulation ability, toxicity, sensitivity, and side effects to sieve out promising drugs suitable for T2D.     

水润滑双螺杆空压机工作过程传热传质特性研究

水润滑双螺杆空压机由于能够提供绝对无油的洁净空气而引起了广泛的关注,为研究水润滑双螺杆空压机内部的传热传质特性,建立考虑干空气-水蒸气-液态水三相流动与传热传质的工作过程模型,并采用p-V图试验数据对计算结果进行验证.经对比发现,模拟结果和试验结果吻合良好,进而通过该模型,研究三相流体传热传质特性.结果 表明,大量的水喷入转子腔仍未实现与湿空气的充分换热,使得湿空气在压缩过程仍有较大温升.而液态水的最大温升也不超过15K,证明了液态水的蒸发是由于液态水表面与湿空气中水蒸气的密度差驱动的对流传质现象.并且,压缩和排气过程的大部分时间对流传质现象为湿空气中的水蒸气冷凝为液态水.因此,压缩过程中湿空气远未达到饱和状态,且随着压缩过程的进行更接近干空气.     

Knowledge-driven digital twin manufacturing cell towards intelligent manufacturing

Rapid advances in new generation information technologies, such as big data analytics, internet of things (IoT), edge computing and artificial intelligence, have nowadays driven traditional manufacturing all the way to intelligent manufacturing. Intelligent manufacturing is characterised by autonomy and self-optimisation, which proposes new demands such as learning and cognitive capacities for manufacturing cell, known as the minimum implementation unit for intelligent manufacturing. Consequently, this paper proposes a general framework for knowledge-driven digital twin manufacturing cell (KDTMC) towards intelligent manufacturing, which could support autonomous manufacturing by an intelligent perceiving, simulating, understanding, predicting, optimising and controlling strategy. Three key enabling technologies including digital twin model, dynamic knowledge bases and knowledge-based intelligent skills for supporting the above strategy are analysed, which equip KDTMC with the capacities of self-thinking, self-decision-making, self-execution and self-improving. The implementing methods of KDTMC are also introduced by a thus constructed test bed. Three application examples about intelligent process planning, intelligent production scheduling and production process analysis and dynamic regulation demonstrate the feasibility of KDTMC, which provides a practical insight into the intelligent manufacturing paradigm.     

An optimization on the stacking line of low-pressure axial-flow fan using the surrogate-assistant optimization method

Journal of Mechanical Science and Technology - The shape of the blade stacking line greatly influences the low-pressure axial-flow fan’s operational efficiency, but there is still no fast and...     

Influence of Turbulence Schmidt Number on Exit Temperature Distribution of an Annular Gas Turbine Combustor using Flamelet Generated Manifold

The Reynolds analogy concept has been used in almost all turbulent reacting flow RANS(Reynoldsaveraged Navier–Stokes)simulations,where the turbulence scalar transfers in flow fields are calculated based on the modeled turbulence momentum transfer.This concept,applied to a lean premixed combustion system,was assessed in this paper in terms of exit temperature distribution.Because of the isotropic assumption involved in this analogy,the prediction in some flow condition,such as jet cross flow mixing,would be inaccurate.In this study,using Flamelet Generated Manifold as reaction model,some of the numerical results,obtained from an annular combustor configuration with the turbulent Schmidt number varying from 0.85 to 0.2,were presented and compared with a benchmark atmospheric test results.It was found that the Schmidt numberσt in mean mass fraction f transport equation had significant effect on dilution air mixing process.The mixing between dilution air and reaction products from the primary zone obviously improved asσt decreased on the combustor exit surface.Meanwhile,the sensitivity ofσt in three turbulence models including Realizable k-ε,SST(Shear Stress Transport)and RSM(Reynolds Stress Model)has been compared as well.Since the calculation method of eddy viscosity was different within these three models,RSM was proved to be less sensitive than another two models and can guarantee the best prediction of mixing process condition.On the other hand,the results of dilution air mixing were almost independent of Schmidt number Sct in progress variable c transport equation.This study suggested that for accurate prediction of combustor exit temperature distribution in steady state reacting flow simulation,the turbulent Schmidt number in steady state simulation should be modified to cater to dilution air mixing process.