页岩气水平井生产套管变形机理及工程应对方案——以昭通国家级页岩气示范区黄金坝区块为例

针对四川盆地周缘昭通国家级页岩气示范区黄金坝区块2口页岩气水平井套管严重变形的情况,基于24臂井径套管变形测量、裸眼井径、电阻率电测、钻时及气测录井、固井CBL/VDL及CBL成像等资料,分析引起套管变形位置附近地层的地质与工程特征,利用三维成像分析软件分析24臂井径测量数据并进行三维成像,得到了变形套管的形态特征。研究结果表明:(1)极严重套管变形井段发生在构造裂缝发育区;(2)套管变形形态为上下方向为主的"S"形弯曲;(3)极严重套管变形呈现明显的遭受岩石高角度滑移挤压而横向剪切变形特征。据此提出建议:(1)该区应重点防范由岩石沿裂缝面滑移引起的剪切套管变形,利用产层段构造等值线图,设计井眼轨迹避开地下局部高陡构造的"脊部"或"谷底"位置;(2)利用产层段蚂蚁体分布图预测的裂缝带分布信息,使井眼轨迹沿裂缝带走向钻进;(3)推荐采用免钻磨大通径桥塞或全通径无限级完井工艺技术,避开压裂后常规桥塞钻磨工序,以确保压裂后的各级压裂层都能投产。     

Urban village demolition,migrant workers' rental costs and housing choices: Evidence from Hangzhou,China

Many cities in China are undergoing large-scale demolition of urban villages. The difficulty of finding suitable housing for migrant workers has caused widespread concern because the lack of proper housing may lead to the outflow of migrant workers that would affect the normal operation of the city. Based on data collected by questionnaire survey in Hangzhou and a multivariate logistic model, this study analyzed the influence of housing demolition on the housing choices of migrant workers. We found that nearly a third (29.2%) of migrant workers spend >30% of their income on rent, and 14.1% of migrant workers plan to return to rural areas. This means that migrant workers face significant housing pressure and some migrant worker outflow from the city exists. Further empirical analysis corroborates that nine variables—including gender, age, education, marriage, occupation, RIR, RRS, HCW, and CMW—have a significant impact on migrant worker housing choices. Based on the results of multivariate logistic regression analysis, we recommend that the government expand the coverage of public rental housing, build temporary low-rent housing, stimulate businesses to provide housing subsidies to their workers, improve the educational conditions for migrant children, and intensively develop long-term, low-income rental apartments.     

固溶温度对激光增材制造Inconel 718合金组织和性能的影响

目的探索激光增材制造Inconel718高温合金最理想的固溶处理制度。方法利用激光增材制造技术制备了Inconel 718合金,通过组织观察(光学显微镜和扫描电镜)、能谱分析和维氏硬度测试等方法,研究了固溶温度对其组织、析出相及硬度的影响。结果不同固溶温度对Inconel 718的晶粒尺寸有很大影响。在固溶温度1000℃下保温1 h,沉积层开始出现再结晶现象。当固溶温度继续增加到1080℃时,与沉积态的组织相比,晶粒明显细化且再结晶过程基本完成。此外,不同固溶温度条件下,Inconel718的相析出和溶解行为也有所差异。固溶温度为940℃时,在未溶解的Laves相周围存在明显的δ相,当固溶温度继续提高时,δ相由于固溶作用而数量减少。另外,不同固溶温度处理后的合金显微硬度也表现出规律变化。当固溶温度为940℃时,试样硬度高于沉积态硬度,但是随着固溶温度持续升高,合金的显微硬度开始迅速下降并低于沉积态硬度,1050℃时保持稳定;当温度高于1150℃时,显微硬度继续迅速下降。结论激光增材制造Inconel718合金的热处理制度不同于铸造和锻造的热处理制度,其较为理想的固溶制度为1080～1150℃保温1 h。     

金刚石粒径及含量对超音速激光沉积金刚石/Cu复合涂层微观结构及性能的影响

目的研究不同金刚石粒径及含量对超音速激光沉积金刚石/Cu复合涂层微观结构及性能的影响。方法利用超音速激光沉积技术制备金刚石/Cu复合涂层。采用扫描电镜和摩擦磨损测试对涂层的显微组织结构和磨损性能进行了分析,用激光闪烁法测量复合涂层的热导率。结果金刚石均匀分布在复合涂层中,原始粉末中金刚石体积分数从30%增加到50%时,复合涂层中金刚石颗粒的面积占比仅从14.01%升至16.79%,远低于金刚石颗粒在原始粉末中的含量。400目金刚石/Cu复合涂层的平均热导率为296 W/(m·K),摩擦系数为0.551;800目金刚石/Cu复合涂层的平均热导率为238 W/(m·K),摩擦系数为0.545。结论原始粉末中金刚石配比的增加并未对复合涂层中金刚石含量的提升有显著作用。金刚石/Cu复合涂层的热导率随着增强相颗粒含量的增加而降低,随着增强相颗粒粒径的增大而提高。不同粒径金刚石颗粒的添加能显著降低Cu涂层的摩擦系数,且小粒径金刚石颗粒的添加使复合涂层的摩擦系数更低和更稳定,从而使其具有更小的磨损量和磨痕宽度,表现出较优的耐磨损性能。     

316L不锈钢激光瞬时退火软化工艺研究

目的解决冲压中加工硬化导致的高强度低塑性的问题。方法提出以矩形光斑的温控模式激光为热源,对工件进行选区瞬时退火,达到局部软化的目的。通过金相显微分析、显微硬度分析、力学拉伸及断口分析,分别评价激光瞬时退火软化后试样显微组织、显微硬度、抗拉强度、断后伸长率和断口形貌。结果金相组织显示,不同工艺条件下的晶粒大致呈现变形晶粒、再结晶晶粒、细小晶粒和较大等轴晶4种状态。由显微硬度可知,固溶态母材硬度为173HV0.2,加工硬化后达到341HV0.2。当激光温控温度为1400℃,扫描速度分别为5、10、15 mm/s时,软化处理后硬度分别为164、173、257HV0.2。而扫描速度一定时,激光温控温度越高,软化处理后硬度越低。对试样做室温拉伸试验发现,激光瞬时退火后强度降低,塑性提高。当温控温度为1400℃,扫描速度为5 mm/s时,抗拉强度由加工硬化后的911 MPa下降到591 MPa,接近固溶态母材的570 MPa,断后伸长率由18.2%恢复到54.7%,达到固溶态母材的95.5%。结论激光瞬时退火软化可有效降低加工硬化后的材料强度,提高材料塑性,使其恢复大变形能力。其软化程度随激光温控温度的降低、激光扫描速度的提高而降低,在较优工艺参数下,激光瞬时软化后性能甚至优于母材性能。     

微纳结构对硅基超疏水表面冷凝特性的影响

目的 研究微米结构中心距对微纳二级结构超疏水硅表面热交换效率的影响。方法 首先采用湿法腐蚀在硅表面构建中心距分别为22、24、26、28、30 μm的微米四棱台结构,然后采用溶胶-凝胶法在表面涂覆疏水的纳米二氧化硅颗粒,获得微纳二级结构超疏水表面。通过表面接触角测量仪分析表面的湿润性,通过扫描电镜观察表面的微观形貌特征,使用光学显微镜观察冷凝小液滴自迁移现象,使用电子天平称量表面的冷凝集水质量。结果 当纳米结构相同时,随着微米结构中心距的增加,液滴静态接触角减小,冷凝小液滴的自迁移频率变慢,相同时间段内,平均集水效率下降。当相对湿度大于90%时,会出现表面“淹没”现象。微纳二级结构超疏水硅表面（微米结构间距22 μm）的集水效率是单独微米结构硅表面的1.38倍、单独纳米结构疏水表面的1.27倍、疏水硅光片表面的1.75倍、光二氧化硅亲水表面的3.6倍。结论 当纳米结构相同时,在一定范围内适当减小微米结构的中心距,有助于增强微纳二级结构超疏水硅表面热交换效率。     

A multiobjective box-covering algorithm for fractal modularity on complex networks

The box-covering method is widely used on measuring the fractal property on complex networks. The problem of finding the minimum number of boxes to tile a network is known as a NP-hard problem. Many algorithms have been proposed to solve this problem. All the current box-covering algorithms regard the box number minimization as the only objective. However, the fractal modularity of the network partition divided by the box-covering method, has been proved to be strongly related to the information transportation in complex networks. Maximizing the fractal modularity is also important in the box-covering method, which can be divided into two objectives: maximization of ratio association and minimization of ratio cut. In this paper, to solve the dilemma of minimizing the box number and maximizing the fractal modularity at the same time, a multiobjective discrete particle swarm optimization box-covering (MOPSOBC) algorithm is proposed. The MOPSOBC algorithm applies the decomposition approach on the two objectives to approximate the Pareto front. The proposed MOPSOBC algorithm has been applied to six benchmark networks and compared with the state-of-the-art algorithms, including two classical box-covering algorithms, four single objective optimization algorithms and six multiobjective optimization algorithms. The experimental results show that the MOPSOBC algorithm can get similar box numbers with the current best algorithm, and it outperforms the state-of-the-art algorithms on the fractal modularity and normalized mutual information.     

Agency costs in public transport systems: Net-cost contracting between the transport authority and private operators - impact on passengers

Drawing on an agency theory approach, this paper examines conflict of interests and the resulting agency costs in the provision of urban public transport services in Istanbul's public transport system, particularly the private bus and minibus operators' relationship with local government. The agency problem in Istanbul's urban mobility system shows itself most explicitly in private bus and minibus operators because of the net-cost (NC) contract model in place. The private bus and minibus operators' relationship with local government is examined as a case study of agency relationships. Conceptually, government transport authorities and transport operators, together with the passengers, are the main actors of this urban public transport system. They all have distinct needs, interests and requirements and interact with each other, all embedded in a specific institutional environment. Service quality provided by public transport operators depends on the positive interactions between these actors. Whereas passengers demand reliable, affordable, safe and comfortable mobility services, private bus and minibus operators aim to increase their revenue and maximise their profits. In contrast to this, government bus operators provide in-house bus services without much concern for profitability. Regulators or local authorities, on the other hand, are expected to set up an institutional environment where passengers' and operators' expectations are met in a satisfactory manner. Empirical analyses and interviews with key agents demonstrate that agency costs are shown to be the result of misaligned interests between the government transport authority and private operators that lead to reduced service quality in terms of safety, comfort, reliability and affordability. We conclude that the agency costs of current NC contracting on passengers in Istanbul has deficiencies and propose instead a performance-based gross-cost (PrGC) contracting model. PrGC contracting can alleviate agency costs by changing the incentives of operators where regulatory and financing mechanisms are not enough to handle NC contracting. Istanbul represents some transferable lessons and implications, especially for developing cities around the world.     

Spectrum pricing for cognitive radio networks with user’s stochastic distribution

Wireless Networks - Amid the dynamic spectrum access in cognitive radio networks, when complex spectrum conditions should be taken into account, how to price the spectrum in order to benefit...     

Have Chinese universities embraced their third mission? New insight from a business perspective

Have Chinese universities, after enormous investment over the past decade, embraced the university’s third mission—contributing to industrial and technological progress? The literature has not sufficiently addressed this question. This study intends to advance understanding of this issue by empirically addressing this question from a business perspective in a bold and unconventional way. Unlike prior studies that simply used contingent and institutional factors to describe the link between Chinese universities and industrial firms by measuring such aspects as patent licensing, co-patenting, and co-authoring, our work goes further and applies longitudinal analysis to examine the ways firms access university-level knowledge and the impact of such knowledge on firm innovation outputs. We propose that if Chinese universities embraced their third mission, then we would observe a positive effect of university–industry collaborations on firms’ subsequent innovation outputs. Empirical results based on a sample of the top 100 Chinese electronic firms in terms of output value support our hypothesis. Specifically, university patent licensing and co-patenting between universities and firms was found to positively affect firm innovation outputs. Moreover, we found that geographical distance and collaboration dominance moderate the co-patenting–innovation output relationship.