Practices,projects and portfolios: Current research trends and new directions

Project portfolio management (PPM) bridges strategy and project management. Traditional research in PPM has primarily investigated the rational, top-down and structural aspects of strategizing. By doing so, it has failed to focus on the underlying practices that are triggered by the strategy and how these practices frame strategy implementation. Practice-based research provides a methodological lens to explore the reality of strategic enactment through the project portfolio. Practice-based perspectives are under-represented in PPM research; therefore the aim of this paper is to provide an agenda for further practice-based research in PPM. Central to this agenda is a concern with various aspects of practice, including its discursivity, representation, dynamic capabilities, leadership and materiality.     

黄河什四份子弯道冰期水流及冰塞特征研究

覆冰条件下,弯道水流固有的三维特性更为复杂,对河流弯道冰下水流特征及冰塞的研究有助于推进防凌减灾工作。依据2020年1月稳封期的原型观测数据,对黄河什四份子弯道冰下水流及冰塞特征进行了详细分析。结果表明,弯顶节点工程引起的回流是阻冰的重要条件,上游下潜的冰花因水动力不足及河势等因素影响发生堆积,冰塞在弯内形成并沿凹岸主槽逐渐向上游发展,同时,弯顶卡冰封河与下游较大的水流流速,促进了清沟的形成;入弯至弯顶区间,冰下水流流速垂线分布基本服从双对数分布规律;受凹岸冰塞及回流影响,纵向上,水流流速呈减小趋势,在弯顶附近开始恢复;径向上,河道主流被冰塞压迫并逐渐趋于凸岸,致使弯道主流易位,凸岸水流流速大于凹岸,清沟向凸岸偏移;弯道水流湍动能与雷诺应力主要在近底处存在较大的变幅,表明近底水流运动活跃,且二者大小与流速大小在径向与纵向分布上具有较好的一致性,受冰盖影响,水流湍动能沿水深近似呈"S"形分布,雷诺应力分布无明显规律。     

Effect of CaO mineral change on coal ash melting characteristics

The change of mineral composition in ash and the effect of CaO on the melting characteristics of coal ash were studied by adding different contents of CaO to coal ash. At the same time, the Factsage thermodynamics software was used to simulate the mineral changes in the synthetic ash to support and verify the experimental results. The results show that with the increase of CaO content, the melting characteristic temperature of coal ash first decreases and then rises. After adding a certain amount of CaO, the quartz with higher melting point completely disappears, and the melting point of the coal ash reaches a minimum value. And with the increase of CaO content, the appearance of wollastonite and single crystal calcium oxide mineral makes the melting point of coal ash gradually increase. It can be seen from the phase diagram calculated by Factsage that as the CaO content increases, the corresponding position of the coal ash gradually moves from the hematite region to the calcareous region. And the phenomenon of low temperature eutectic occurs when the CaO content is 35%, which is consistent with the trend of temperature change of the melting characteristics. These phenomena all indicate that the change in the melting point of coal ash is nonlinear as the content of CaO minerals increases.     

浅析煤矿综采放顶煤安全开采问题

以煤矿放顶煤安全开采问题为对象开展分析探究。结合具体工程实际,在分析综放工艺技术特征的基础上,对综采放顶煤安全开采需注意的问题与防范措施开展深入分析,希望能够为其他矿井综放开采的有效开展提供借鉴和帮助。     

A Proposal for Addressing Security Issues Related to Dynamic Code Loading on Android Platform

One of the constant challenges faced by the Android community, when it comes to the safety of the end users, is the ability of applications to load code dynamically. This mechanism may be used for both legitimate and malicious purposes. A particular problem is the fact that remote code is not analyzed during the verification process because it doesn’t have to be present in the application package at the publishing time. Previous research has shown that using this concept in an insecure way can cause serious consequences for the user and his device. Solving this problem has proved to be a big challenge that many have tried to address in different ways. This paper deals with the problem of dynamic code loading on Android platform. For the purpose of this paper, an application that demonstrates the abuse of the dynamic code loading concept has been developed and published in the Google Play Store. Also, a proposal of the modified Android ecosystem that should address this problem and improve the security of the whole platform is given.     

The control of paracetamol particle size and surface morphology through crystallisation in a spray dryer

The parameters governing the crystallisation of paracetamol using various conventional techniques has been extensively studied, however the factors influencing the drug crystallisation using spray drying is not as well understood. The aim of this work was to investigate the crystallisation of an active pharmaceutical ingredient through evaporative crystallisation using a spray dryer to study the physicochemical properties of the drug and to use semi-empirical equations to gain insight into the morphology and particle size of the dried powder. Paracetamol solutions were spray dried at various inlet temperatures ranging from 60 °C to 120 °C and also from a series of inlet feed solvent compositions ranging from 50/50% v/v ethanol/water to 100% ethanol and solid-state characterisation was done. The size and morphology of the dried materials were altered with a change in spray drying parameters, with an increase in inlet temperature leading to an increase in particle Sauter mean diameter (from 3.0 to 4.4 µm) and a decrease in the particle size with an increase in ethanol concentration in the feed (from 4.6 to 4.4 µm) as a result of changes in particle density and atomised droplet size. The morphology of the dried particles consisted of agglomerates of individual crystallites bound together into larger semi-spherical agglomerates with a higher tendency for particles having crystalline ridges to form at higher ethanol concentrations of the feed.     

中国大气田科学开发的内涵

大气田是指天然气探明地质储量超过300×10~8 m~3、天然气峰值年产量在10×10~8 m~3以上且具有一定稳产期的气田。其是中国天然气储产量快速增长和未来长期稳定发展的重要基础,也是保障我国供气安全的关键。通过对国内外260余个大气田开发实践的系统分析和典型气田的解剖模拟,综合研究了大气田科学开发的内涵、核心技术以及全生命周期指标体系。大气田科学开发的内涵包括:①提出以"识别水、控制水、治理水"为技术体系的天然气开发理念,即常规气田"控水开发"、非常规气田人工压裂"注水开发",根据气藏类型和气藏特征,确定合理的采气速度;②综合评价气田开发经济效益和社会效益,保障气田长期稳产;③根据气井生产特征和储层发育特征,选取适用的气田稳产方式;④依据对常规与非常规气藏不同开发阶段的精细描述、气藏开发特征和生产动态的监测,确定气田可采储量、气田水与人工注水开发规律、气田提高采收率技术对策、气田效益稳产期与发展战略。大气田科学开发的核心技术包括:规模优化技术、科学布井技术、均衡开采技术和深度挖潜技术。进而综合优选出产量、压降、采出程度、单位压降产量等多个参数作为评价大气田科学开发的关键指标,建立了高压、低渗透—致密、裂缝—孔隙型和页岩气等4类气藏的全生命周期指标体系。结论认为,该研究成果有助于指导不同类型大气田的科学开发,进一步促进我国天然气产业的快速发展。     

Morondava盆地西部侏罗纪断陷盆地构造特征

系统分析了Morondava盆地西部侏罗纪断陷盆地构造特征,实可分为东部断陷带、中部断裂构造带和西部侏罗系残留斜坡带,可能存在有断鼻型、背斜型、地层剥蚀尖灭型、断块型、古潜山及岩性圈闭。     

甘肃省陇东地区极端降水的时空特征

为阐明甘肃省陇东地区极端降水的变化规律,利用该地区13个气象台站1961~2015年的逐日降水资料,应用超门限峰值法、反距离加权法、线性倾向估计法、滑动平均法、Mann-Kendall突变分析法、复值Morlet小波分析法研究极端降水的时空变化特征。结果表明,陇东地区各站第95百分位极端降水阈值在27.8mm附近变化,即可以大雨事件作为极端降水事件进行监测;极端降水指数主要表现为从南向北递减的趋势,极端降水事件对环县和崆峒的影响较小;极端降水事件虽然在总量、强度上表现为减小趋势,但其发生频次及对总降水的贡献率逐渐增强;极端降水总量和极端降水强度周期变化均在21年左右能量最强,而极端降水频次和极端降水贡献率周期变化分别在28、5年左右能量最强。     

Analysis and optimisation of particle mixing performance in fluid phase resonance mixers based on Euler/Lagrange calculations

A novel mixing principle utilising oscillating liquid columns was analysed numerically with regard to particle dispersion characteristics. For producing fluid oscillations a pipe (diameter 100 mm) was immersed centrally into a vessel (diameter 450 mm) filled with liquid (filling height 700 mm) and periodically pressurised (frequency 1.2 Hz). The outlet geometry of the central pipe, just ending near the vessel bottom, has a strong effect on mixing and was optimised in this study. The principle of a FPR-mixer does not require rotating stirrers and in the turbulent regime it has power numbers comparable to propellers. The numerical calculations were conducted by a Euler/Lagrange approach neglecting two-way coupling as well as inter-particle collisions for clarity in order to only focus on the effect of interfacial forces on particle dispersion. The continuous phase was calculated in an unsteady way based on the Reynolds-averaged equations combined with the k-ω-SST (shear stress transport) turbulence model. Lagrangian tracking was conducted considering all relevant forces; drag, gravity/buoyancy, fluid inertia, added mass, Basset force and transverse lift forces due to shear and particle rotation. The importance of these forces was analysed with respect to the turbulent particle Stokes number (considered range 0.004 < St < 10.0) and particle/liquid density ratio (i.e. 1.05, 1.5 and 2.5). Finally, the significance of Basset force and shear-rotation lift force (i.e. Magnus effect) on the dispersion process was quantified by mixing parameters.