Failure analysis of polycrystalline diamond compact cutters for breaking rock by bending waves theory

The breakage mechanism of the polycrystalline diamond compact(PDC) cutters was analyzed by the energy theory of bending waves. The cutting tests of granite block were conducted on a multifunctional testing device by using the cutter at three kinds of negative fore angles of 30°, 45° and 60°. The results show that, when the edge of the PDC layer is broken, the layer of tungsten cobalt is broken a little under the angle of 30°, while the layer of tungsten cobalt is broken continuously under the angle of 60°, their maximum depths are about 2 and 7 mm respectively in the two cases. The eccentric distance mainly depends on the negative fore angle of the cutter. When the cutter thrusts into the rock under an attack angle of 60°, the energy of bending waves reaches the maximum since the eccentric distance is the maximum. So the damage of cutter is the most serious. This test result is consistent with the conclusion of theoretical analysis well. The eccentric distance from the axial line of cutter to the point of action between the rock and cutter has great effect on the breakage of the cutter. Thus during the process of cutting, the eccentric distance should be reduced to improve the service life of PDC cutters.

建立在波特菱形理论上的中国电炉企业对外贸易竞争优势分析

当涉及国家的贸易发展水平时,贸易竞争优势被认为在一定程度上起着决定性的作用。然而,目前关于国家贸易竞争优势的分析研究存在着不完善的问题。为此,本研究利用波特菱形理论对中国电炉企业对外贸易竞争优势展开深入分析。在探讨波特菱形理论的基础上,从生产要素、需求条件、相关产业配套和企业发展战略等方面研究中国电炉企业对外贸易竞争力。再对波特菱形理论和竞争力分析结果进行充分利用,从贸易机会、产业结构等方面进行详细分析,以判断中国电炉企业对外贸易活动所具有的竞争优势。通过综合考量,以深入了解中国电炉企业在全球贸易竞争中的地位和潜力,实现全面评估中国电炉企业在国际市场中的竞争优势的目标,以为其未来的发展提供战略指导。

对外直接投资对产能过剩的影响——基于供给和需求双重视角的分析

改革开放以来,我国对外开放水平不断提升,逐步形成高水平的对外开放格局,产能过剩问题也得到不断改善。本文在梳理我国产能过剩的内涵和成因基础上,基于“供给侧—需求侧”分析框架,探讨了对外直接投资缓解产能过剩的内在机制。在供给侧方面,对外投资使得边际产业转移,生产要素跨国流动,并且产生逆向技术溢出效应,从而提高产能的利用率来缓解产能过剩。在需求侧方面,对外直接投资产生了出口效应和国际竞争效应,从而提高产品需求来缓解产能过剩。最后,本文认为对外直接投资的蓬勃发展可以从供给侧和需求侧两方面改善我国的产能过剩现象,仅供参考。

First-Principle Calculations for Elastic and Thermodynamic Properties of Diamond

The elastic constants and thermodynamic properties of diamond are investigated by using the CRYSTALO3 program. The lattice parameters, the bulk modulus, the heat capacity, the Gruneieen parameter, and the Debye temperature are obtained. The results are in good agreement with the available experimental and theoretical data. Moreover, the relationship between V/V0 and pressure, the elastic constants under high pressure are successfully obtained. Especially, the elastic constants of diamond under high pressure are firstly obtained theoretically. At the same time, the variations of the thermal expansion α with pressure P and temperature Tare obtained systematically in the ranges of 0-870 GPa and 0-1600 K.

Fluctuations of electrical and mechanical properties of diamond induced by interstitial hydrogen

While experimental evidence demonstrates that the presence of hydrogen（H） impurities in diamond films plays a significant role in determining their physical properties, the small radius of the H atom makes detecting such impurities quite a challenging task. In the present work, first-principles calculations were employed to provide an insight into the effects of the interstitial hydrogen on the electrical and mechanical properties of diamond crystals at the atomic level. The migrated pathways of the interstitial hydrogen are dictated by energetic considerations. Some new electronic states are formed near the Fermi level. The interstitial hydrogen markedly narrows the bandgap of the diamond and weakens the diamond crystal. The obvious decrement of the critical strain clearly implies the presence of an H-induced embrittlement effect.

Effective-field and Monte Carlo studies of mixed spin-2 and spin-1/2 Ising diamond chain

The magnetic properties of a mixed spin-2 and spin-1/2 ferromagnetic diamond chain are studied by effective-field theory and Monte Carlo（MC） simulation based on the Ising model.The temperature dependences of magnetization,magnetic susceptibility,internal energy,and specific heat are studied,respectively.The exchange interaction dependences of magnetization and the critical temperature are calculated by MC simulation.The changes of magnetization depending on the field increasing and then the field decreasing under steady-static conditions are also given.

Valence band offsets of the strained and longitudinally relaxed diamond/c-BN superlattices

The valence band offsets of the strained and longitudinally relaxed diamond/cubic boron-nitride （c-BN） （110） superlattice are investigated by the plane wave density functional theory approach and using the on-site core electron as a reference energy level. For the strained diamond/c-BN superlattice, the valence band offset of around 1.50 eV is in good agreement with those using all the electrons methods. As for the longitudinally relaxed superlattice, the valence band offset of around 1.28 eV is smaller than that of the strained superlattice. The reason for this is mainly due to the split of the valence band maximum caused by the anisotropic strain.

Diamond Model Based Analysis on Cooperation between of Poverty Alleviation and Emission Reduction in Agricultural Counties: A Case Study of Huoshan County in Anhui Province

2020 is the year of decisive stage for building a well-off society in an all-round way.On the winter vacation of 2020,we went to Huoshan County,Anhui Province,an old revolutionary area,and conducted a social survey for nearly a month.Through interviews,on-site observations,and access to materials,we clearly found that the local party committee and government actively responded to the call of the state,practiced the"two mountains"theory,turned a poor and backward agricultural county into a national ecologically civilized and well-off county,and realized the coordinated progress of poverty alleviation and energy conservation and emission reduction.Starting from the government policies and rural facts of Huoshan County,a national ecological county,and using Porter’s"Diamond Model",our team used Huoshan County’s environmental advantages and disadvantages,economic prosperity and decline as comparison conditions,and analyzed external factors such as factor conditions,opportunities,related and supporting industries,government forces,etc.,to come up with pertinent recommendations for the development of agricultural county-level characteristic industries.

文化菱形视域下的馆地协同运河文化国际推广

中国大运河是文化国际交流的宝贵资源,也是国家形象构建的重要内容,如何有效推广是一项现实难题。依托文化菱形理论建构的运河文化国际推广菱形图式为图书馆与地方协同推广大运河文化、提高运河文化的国际知名度提供了新的思路。图书馆以其特有的文献和空间优势,通过与地方的共建、委托、派驻、基地等协同模式,采用整体共用、文献共享、居民教育、技术应用、媒体合作等技术路线,有效开展运河文化的国际推广。文章为图书馆传承文化的探索提供了一个新的视角。

基于欺诈菱形理论模型的参保人违规行为倾向及其影响因素甄别

目的:了解参保人违法违规行为倾向,甄别其影响因素,为针对性治理参保人违法违规行为提供参考。方法:基于欺诈菱形理论模型,对733名参保人开展问卷调查,采用一般描述性统计、单因素分析和多元线性回归等对参保人违法违规行为倾向进行分析研究。结果:参保人的医保违规倾向总体水平为1.47分±1.356分,医保违规倾向较高的受访者占25.37%。医药行业存在潜规则这一机会诱因(β=0.107),参保人的身体健康压力(β=0.148)、外借社保卡是助人行为(β=0.189)和医保违规不会被发现和处罚(β=0.107)等自我合理化因素,以及在医疗—医药—医保系统认识熟人(β=0.157)和具备作案条件、渠道和工具(β=0.147)等能力因素,均对参保人违法违规行为倾向有显著影响。结论:加强多部门协作和智能监管,提升参保人的身体健康水平,推进医保法治和道德教育宣传,纠正参保人的非理性认识,强化医疗服务供方职业道德教育。

金刚石中La相关缺陷的结构稳定性和电子结构

利用密度泛函理论(DFT)对金刚石La色心结构进行优化,并在VASP软件包中进行计算。发现金刚石LaV3结构最稳定,La原子位于三个空位中心的取代基位置。在此基础上,计算了其电子结构。测定了La和C的电荷转移、能带结构和态密度。能带中的杂质态主要由La原子的6s和5d轨道组成,激发态位于前者,基态位于后者。计算得到金刚石LaV3色心的零声子线为2.01126eV,相应的荧光波长为598.63nm。为金刚石LaV3色心的制备和应用提供了参考。

基于钻石理论的民办养老设施竞争力研究--以杭州市为例

老龄化背景下,如何提升民办养老设施的竞争力已成为新时代我国养老事业建设必须面对与重视的核心问题。基于钻石理论构建民办养老设施的评价指标体系,以杭州市民办养老设施POI数据为基础,运用核密度估计、障碍度模型等方法分析杭州市民办养老设施竞争力空间分布特征及其影响机理。研究结果显示:杭州市民办养老设施竞争力水平空间上呈现“核心边缘”特征;高竞争力民办养老设施紧邻主干道空间分布,与医疗设施、高房价区域、老年人口密度分布有较强一致性;床位数、街道/区县老年人口密度、周边房价、人均护理人员数量是影响竞争力提升的主要因子。

乡村振兴背景下大学生返乡创业影响因素研究

为激发大学生返乡创业动力,助力乡村振兴,以返乡创业的大学生为研究对象,探讨大学生返乡创业的影响因素。通过扎根理论,对不同高校与地区的大学生返乡创业者进行访谈调研,构建了大学生返乡创业影响因素“钻石模型”,大学生返乡创业者受心理资本、创业项目实现、创业教育资本、创业社会资本4个因素影响。研究表明,各因素间有着主次关系、相互促进,具有时代与地区差异性。社会、高校、家庭加强创新创业综合素质与技能的教育,给予学生创业政策指导,提供多方面创业支持将有助于推进大学生返乡创业。

“璇玑”系统钻头选型研究

“璇玑”系统是中海油服自研旋转导向及随钻测井系统,目前已经完成1000口井的作业。为了使“璇玑”系统保持竞争力并得到进一步推广,“璇玑”系统配接的钻头选型至关重要。基于“璇玑”系统导向工具的结构特征和导向机理,阐述钻头选型的原则和方法,从“璇玑”系统应用角度提出适合该系统应用的钻头选型方法,并通过实钻实验分析得到钻头选型的特征参数,从而总结出“璇玑”系统在钻头选型方面的原则,可为“璇玑”系统推广应用提供技术参考和理论依据。

基于钻石理论的主导产业选择模型的研究

学术界和产业界关于主导产业选择的理论和实证研究层出不穷,研究思路、方法、指标选择等主要沿袭比较优势理论、产业关联理论、经济增长理论和筱原三代平准则的相关内容,而上述研究方法的应用需要有大量的产业发展数据为支撑,因而在我国西部经济欠发达地区的应用上存在局限。本文以比较优势和竞争优势理论为基础,建立主导产业选择模型,提出了主导产业选择的评价指标体系及模型计算方法,并进行了实证研究。

仿生非光滑理论在钻井工程中的应用与前景

仿生学是一门可与很多学科交叉的边缘性学科,同样与钻井工程技术的融合也将产生创新性成果。在分析仿生非光滑表面减阻、防黏和耐磨特性的基础上,将该理论引入到钻头设计中,研制仿生金刚石钻头。以蜣螂为仿生原形,设计孕镶金刚石钻头的工作层,使工作层底唇面始终具有相同的非光滑形态,始终保持高钻速和长寿命,突显出仿生金刚石钻头的高效率、耐磨和减阻特点。试验结果表明,仿生钻头较普通钻头钻速提高44%、使用寿命增加74%。此外,仿生非光滑表面结构所具有的各种特性可用于改善钻井工程中相对运动的摩擦或滑动部件的使用寿命和工作环境,如可提高钻头、钻杆接头、泥浆泵活塞和缸套的耐磨性,解决钻头泥包问题,减少螺旋钻具和冲击挤密矛头阻力等,应用前景广阔。

基于“钻石”理论的中国绿色食品产业发展思考

文章运用“钻石”理论,对影响我国绿色食品产业发展的关键因素进行了深入的分析,认为我国绿色食品的产业竞争力还没有形成。由此提出应通过加速国内市场需求的启动,提升相关产业的竞争力,以及发展有特色的绿色食品产业群等措施来推动我国绿色食品产业的发展。

基于钻石理论对区域旅游合作中产业集群的探讨

根据迈克尔.波特的"钻石理论",首次构建了"区域旅游合作的钻石模型",并以此为理论框架,分析了区域旅游合作的影响因素.在此基础上,探讨了区域旅游合作的钻石模型对旅游产业集群的几点启示:第一,根据市场需求布置旅游产业集群;第二,围绕核心旅游资源集聚;第三,建立良好的竞合关系;第四,健全相关与辅助产业.

区域生产性服务业发展主导产业选择模型研究

研究了区域生产性服务业发展主导产业选择模型。通过分析和总结主导产业选择的准则、指标和方法,提出了基于钻石理论的区域生产性服务业主导产业选择的指标体系,利用整体有效的DEA模型来反映各行业绩效,利用AHP反映政府在产业选择过程中起到的作用,构建了区域生产性服务业主导产业选择模型,并通过实证分析,证实了该模型的可行性。

经济不发达地区旅游开发的一种模式研究——湖南城步苗族自治县旅游开发实证分析

文章根据迈克尔·波特钻石理论和企业核心竞争力理论,对湖南城步苗族自治县旅游开发进行了实证分析,探索和构建了城步县旅游发展的钻石体系,结合城步的实际提出几点建议,同时也为经济不发达地区旅游开发提供一种探索性模式。