高效聚合物钻井液泥饼润滑剂的研制及其作用机理分析

为改善井壁泥饼在水平井和大位移井钻进至中后期的润滑性,研发了一种能有效降低水平段摩阻的固体粉末状高效聚合物水基钻井液泥饼润滑剂RHGXJ-3（羧酸共聚物、针状硅酸盐、聚丙烯微粉质量比为10∶11∶2）,通过测定泥饼黏滞系数、温度敏感性和钻井液配伍性,明确泥饼润滑剂RHGXJ-3 的作用效果和适用条件,并结合SEM和XRD微观表征技术分析该泥饼润滑剂的润滑机理。研究结果表明,将泥饼润滑剂以0.9%的加量加入井浆并制得泥饼,静置1 min 后测得的泥饼黏滞系数相较于加剂前从0.0966 降为0.0496,泥饼润滑性提高了48.65%。温度敏感性测试结果表明该泥饼润滑剂的适用温度为30～120 ℃。该泥饼润滑剂与钻井液的配伍性良好,0.9%的加量下可将井浆的漏斗黏度由55 s 降至39 s,井浆流动能力提升29.1%。该润滑剂够在泥饼表面和内部生成溶剂化水膜和凝胶类物质,通过填充空隙、提升压缩性等途径提高泥饼的润滑性,降低泥饼摩阻。与石墨和球状固体润滑剂相比,润滑剂RHGXJ-3 的泥饼润滑效果更佳,是其它固体润滑剂的1.6～2.2 倍,而使用成本则降低约50%。     

一种基于多窗宽度STFT的PSWFs信号时频分析方法

固定窗宽度的短时傅里叶变换(Short Time Fourier Transform,STFT)时频分辨率是固定的,难以对频率时变的椭圆球面波函数(Prolate Spheroidal Wave Functions,PSWFs)信号的时频分布特性进行全面分析.剖析了窗宽度对不同参数PSWFs信号STFT时频分布的影响,...     

用于肌肉电信号控制的仿生机械手设计与仿真

针对肌肉电信号(EMG)控制假手的需求,介绍了一种仿生机械手的设计和控制仿真.此机械手优势在于关节和手指尺寸完全还原真实人手的大小.首先,在多自由度的基础上,建立了五指的运动学模型并求出其运动学正解和逆解.然后,通过仿真来验证其运动学解的正确性,从而为仿生机械手的运动轨迹规划和进一步的控制提供了理论依据.最后,简要说明...     

分层型蓄冷水箱中扩散器的设计与实验研究

对影响分层型蓄冷水箱性能的因素进行了分析，其中扩散器对蓄冷水箱的性能有着重要影响。提出了扩散器设计的基本假设及方法。按照该设计方法建立了分层型蓄冷水箱实验装置，通过了110分钟的蓄、放冷实验研究，验证了扩散器设计的基本假设、方法的合理性。实验结果表明：按照分层型蓄冷水箱中扩散器的设计条件，可以保证分层型蓄能水箱经济、可靠地运行。     

Who tends to answer open-ended questions in an e-service survey? The contribution of closed-ended answers

This study presents a web survey investigating the effects of gender, age, prior usage behaviours, and closed-ended answers on response behaviour for open-ended questions in a user satisfaction or experience evaluation. Two types of open-ended questions were measured: general comment-specific questions designed to collect comments and explanation-specific questions designed to determine the reason for a higher or lower score for the closed-ended questions. Using an online structured questionnaire on an e-service telecom website, 13,346 valid responses (73.1% male; all aged 19 or above) were analysed. More than 75% of the respondents did not answer any of the open-ended questions. Although respondents tended to answer comment-specific questions (19.9%) more often than explanation-specific questions (11.9%), personal characteristics emerged as significant predictors of participants’ response behaviour in both types of open-ended questions. Males, younger participants, and those who had more e-service usage behaviours answered more often than other participants. Regarding the relationship between answers in closed-ended and open-ended questions, respondents’ scaled scores were significant predictors of responses to open-ended questions, particularly comment-specific questions. This study suggests that a score of four on a five-point scale may indicate an interesting answer, with negative responses (5.5%) more likely than positive responses (3.9%).     

Phenothiazine‐Based Organic Catholyte for High‐Capacity and Long‐Life Aqueous Redox Flow Batteries

Redox‐active organic materials have been considered as one of the most promising “green” candidates for aqueous redox flow batteries (RFBs) due to the natural abundance, structural diversity, and high tailorability. However, many reported organic molecules are employed in the anode, and molecules with highly reversible capacity for the cathode are limited. Here, a class of heteroaromatic phenothiazine derivatives is reported as promising positive materials for aqueous RFBs. Among these derivatives, methylene blue (MB) possesses high reversibility with extremely fast redox kinetics (electron‐transfer rate constant of 0.32 cm s^?1), excellent stability in both neutral and reduced states, and high solubility in an acetic‐acid–water solvent, leading to a high reversible capacity of ≈71 Ah L^?1. Symmetric RFBs based on MB electrolyte demonstrate remarkable stability with no capacity decay over 1200 cycles. Even concentrated MB catholyte (1.5 m ) is still able to deliver stable capacity over hundreds of cycles in a full cell system. The impressive cell performance validates the practicability of MB for large‐scale electrical energy storage.     

Stochastic systems simulation optimization

With the advance of new computational technology, stochastic systems simulation and optimization has become increasingly a popular subject in both academic research and industrial applications. This paper presents some of recent developments about the problem of optimizing a performance function from a simulation model. We begin by classifying different types of problems and then provide an overview of the major approaches, followed by a more in-depth presentation of two specific areas: optimal computing budget allocation and the nested partitions method.     

Mixed integer programming in production planning with backlogging and setup carryover: modeling and algorithms

This paper proposes a mixed integer programming formulation for modeling the capacitated multi-level lot sizing problem with both backlogging and setup carryover. Based on the model formulation, a progressive time-oriented decomposition heuristic framework is then proposed, where improvement and construction heuristics are effectively combined, therefore efficiently avoiding the weaknesses associated with the one-time decisions made by other classical time-oriented decomposition algorithms. Computational results show that the proposed optimization framework provides competitive solutions within a reasonable time.     

Mathematical models for capacitated multi-level production planning problems with linked lot sizes

Various mixed-integer programming models have been proposed for solving the capacitated multi-level lot sizing problem with linked lot sizes. It would be of value for researchers and practitioners to know which of these models is the most efficient under different circumstances. To investigate the comparative efficiencies associated with these models, this paper therefore demonstrates theoretically the relationships between these models when the integrality requirement is relaxed for any subset of binary setup and setup-carryover variables, shows the relative effectiveness of these models in obtaining lower bound solutions associated with linear programming relaxations, and evaluates the relative computational resources and the time needed when using these models through intensive computational tests. These theoretical and numerical results are expected to provide significant guidelines for choosing an effective formulation for different situations.     

An efficient dictionary learning algorithm and its application to 3-D medical image denoising

In this paper, we propose an efficient dictionary learning algorithm for sparse representation of given data and suggest a way to apply this algorithm to 3-D medical image denoising. Our learning approach is composed of two main parts: sparse coding and dictionary updating. On the sparse coding stage, an efficient algorithm named multiple clusters pursuit (MCP) is proposed. The MCP first applies a dictionary structuring strategy to cluster the atoms with high coherence together, and then employs a multiple-selection strategy to select several competitive atoms at each iteration. These two strategies can greatly reduce the computation complexity of the MCP and assist it to obtain better sparse solution. On the dictionary updating stage, the alternating optimization that efficiently approximates the singular value decomposition is introduced. Furthermore, in the 3-D medical image denoising application, a joint 3-D operation is proposed for taking the learning capabilities of the presented algorithm to simultaneously capture the correlations within each slice and correlations across the nearby slices, thereby obtaining better denoising results. The experiments on both synthetically generated data and real 3-D medical images demonstrate that the proposed approach has superior performance compared to some well-known methods.