超声波法提取五倍子天然染料的工艺研究

文章探讨了时间、温度、料液比和pH值等因素对超声波法提取五倍子染料效果的影响,通过正交试验确定了最佳提取工艺。     

Σ-ΔA/DC频谱补偿的研究

Σ -ΔA/DC的数字滤波通常使用SINC3滤波器 ,该滤波器通带内带宽很窄 ,对于较高频率的信号衰减过大 ,严重限制Σ -ΔA/DC的应用。本文研究两种频谱补偿的方法 ,以改善Σ -ΔA/DC带宽 ,并以心电信号为例给出频谱补偿后的结果     

Time between events control charts for gamma distribution

Modern and emerging techniques of technology have brought a revolution in quality inspection of products. When events in highly efficient production processes occur rarely, it requires to inspect and monitor the time between occurrence of these events (TBE). The exponential and gamma distributions are commonly used models for time between events (TBE) data. In this article, a new monitoring scheme has been established for TBE data based on exponential and gamma distributions. In a previous research, transformation-based control charts have been developed for TBE. The proposed study is aimed to use the exact probability distribution of charting statistic rather than applying transformations to data and this has remained still unaddressed. Average run length (ARL) and percentage decrease in ARL (ΔARL) have been calculated using Monte Carlo simulations and the proposed monitoring method has been compared with existing techniques applied to transformed data. The proposed scheme provides a simpler design structure and better performance on different sample sizes in identifying annoying process variations. Further, the technique has been applied to simulated and real-life data sets of time between manufacturing plant accidents to highlight the worth and particle applicability of the proposed work.     

高精度电容式MEMS加速度计系统设计

在传统Σ-Δ架构基础上,引入了低精度高速模/数转换器(ADC),将前置放大器输出的模拟电压信号转换为数字信号,有利于简化电容式微电子机械系统(MEMS)加速度计系统模拟接口电路设计.在嵌入ADC的MEMS加速度系统中,采用过采样平均数字算法对信号进行估计,有效降低系统对前置放大器噪声性能的需求,利于实现低功耗和高精度的设计目标.仿真结果表明:与未采用过采样平均技术相比,当前置放大器输出等效噪声大于1μV/Hz时,系统的信噪比(SNR)提高了约10dB.     

关于井中三分量磁测数据处理的研究

文章以安徽某矿区钻孔三分量测井为例,并结合磁化率测量资料,分析引起异常的地质原因,有效发现旁侧矿体,为矿区找矿积累了经验.     

Theoretical and experimental study on hydrodynamic characteristics of fluidization in air-sand conical beds

This work was aimed at modeling hydrodynamic characteristics of fluidization in conical beds using quartz sand as the inert bed material and air as the fluidizing agent. The minimum fluidization velocity, u_mf, and the minimum velocity of full fluidization, u_mff, were determined by Peng and Fan's models modified for conical fluidized bed. Meanwhile, the pressure drop across a bed, Δp (including Δp_max and Δp_mff corresponding to u_mf and u_mff, respectively), was predicted by using modified Ergun's equations for variable superficial air velocity at an air distributor, u₀. The predicted results were validated by experimental data for some operating conditions. Effects of the sand particle size, cone angle and static bed height on the fluidization pattern and hydrodynamic characteristics are discussed. With the proposed models, the Δp-u₀ diagram were obtained with rather high accuracy for the conical air-sand beds of 30-45^° cone angles and 20-30 cm static bed heights, when using 300- sand particles. For the predicted u_mf and u_mff, the relative computational errors were found to be within 20% for wide ranges of operating variables, whereas Δp_max and Δp_mff could be predicted with lower (10-15%) relative errors. With higher cone angles and/or bed heights, the computational accuracy was found to deteriorate.     

变极式三相异步电机用于石油钻机绞车传动控制的研究

石油钻井用电动钻机有交流电机驱动绞车的传动系统,绞车的调速是通过电机的变频调速和机械传动比变换联合实现的。文章介绍了钻机绞车工况对传动的需求和变极三相异步电动机Δ/YY的变极调速特性,并以此设计一种新型石油钻机用绞车机电传动系统。     

About the role of residual stresses and surface work hardening on fatigue ΔKth of a nitrided and shot peened low-alloy steel

Nitriding and shot peening are surface treatments widely used to improve the fatigue strength of mechanical and structural components. Both treatments enhance the mechanical properties of the surface layer of material: nitriding mainly by means of chemical transformations and formation of a very hard case, shot peening mainly due to compressive residual stress field in the sub-surface layer of material.The combined application of nitriding and shot peening has not been adequately investigated in literature and the known data do not allow to define a general criterion to assess if and when shot peening application after nitriding can be useful. In this paper the effect of nitriding plus shot peening on fatigue strength of a low-alloy steel is investigated by means of experimental tests carried out on specimens containing a micro-hole, acting as a pre-crack. To analyse the role played by shot peening induced residual stresses, a series of specimens was heat-treated after shot peening, being the aim the partial removal of residual stresses without strongly modifying the mechanical properties of the surface layer of material. After a critical discussion of the results in terms of residual stress, micro-hardness trend and fatigue strength, an original fracture mechanics based approach is proposed to predict the threshold value of the stress intensity factor of nitrided and shot peened steels. The results are in good agreement with the experimental evidence.     

Time-dependent analysis of RC frame structures considering construction sequences

This paper deals with a time-dependent analysis of reinforced concrete (RC) frame structures considering the construction sequences. Because of the non-mechanical deformations induced by the time-dependent deformations of concrete, concrete structures usually present different behaviors when the construction sequences are changed, despite having the same structural configurations. Therefore, the time-dependent effects of concrete such as creep and shrinkage must be taken into consideration to simulate the actual behavior of RC frame structures. The material nonlinearity including the cracking of concrete is taken into consideration, and geometric nonlinearity due to the P-Δ$\mathrm{\Delta }$ effect is also taken into account by using the initial stress matrix. In addition, the creep deformation of concrete is described in accordance with a first-order algorithm based on the expansion of a degenerated kernel of the compliance function. Finally, correlation studies with previous numerical results and experimental data are conducted to verify the validity of the proposed model. An analysis of a 10-story RC frame structure is carried out to assess the differences in structural responses according to the construction sequences.     

A Novel Modified Robust Load Frequency Control for Mass-Less Inertia Photovoltaics Penetrations via Hybrid PSO-WOA Approach

Abstract

The high penetrations of distributed energy resources (DERs) leads to severe problems such as reducing system inertia and increasing the frequency deviations from the nominal value. The main target of this study is to enable modern photovoltaics (PVs) with large penetration amounts to participate effectively in the load frequency control in the interconnected power systems, in which frequency and tie-line power sharing deviations exist. In this research, a model for the solar PV is developed to help study the heavy penetration of the solar PVs within interconnected power systems. Secondly, a time domain objective function based on the norm of the area control error is formulated. Thirdly, in order to tune the PI controllers, a combined meta-heuristic algorithm based on particle swarm optimization and whale optimization algorithm (PSO-WOA) is developed and compared with the individual PSO and WOA controllers. From the studied scenarios, the developed combined scheme outperforms the other algorithms in terms of system performance indices. Therefore, the developed PSO-WOA approach is plausible and straightforward to solve many engineering problems as it benefits from the exploitation characteristics of the conventional PSO and the exploration features of the WOA.