Fracture Stimulation by Nano-assisted Foam-based Fluids in High-Temperature Reservoirs

Fracture stimulation, or hydraulic fracturing, has been increasingly implemented to extract and enhance oil and gas production from unconventional resources with very low permeability. In this stimulation technique, fracturing fluid is injected at very high pressure into the underground to initiate and propagate fractures at the target reservoir interval. Proppants, such as coated sands and ceramic, are mixed within the fracturing fluid and distributed inside the fractures to keep the fractures open and maintain the conductive pathways for oil and gas flows. Therefore, fracturing fluids must have sufficient stability and viscosity to suspend, transport and place proppants deep into the fracture system. Liquid foam has been an attractive alternative to conventional water-based fracturing fluids, especially in water-sensitive or under-pressured reservoirs. Implementing fracturing foams offers several practical benefits, such as low water consumption, reduced formation damage, low leak-off rate and high efficiency in transporting and distributing proppants in the fractures. However, while surfactant agents are mainly used to generate and stabilize liquid foams, they tend to degrade very quickly at high temperatures and high salinity, resulting in reduced stability and poor performance of fracturing foams at reservoir conditions. The main aim of this study is to develop an optimized foam-based fracturing fluid with sufficient stability and adequate proppant transportation capacity under harsh reservoir conditions. Furthermore, the stabilization effects of nanoparticles and surfactants on the properties of liquid foams are investigated by a wide range of surface and bulk-scale experiments and fracture simulation modelling. The experimental results show that the synergy between surfactants and silica nanoparticles (SNP) has massive impacts on the properties of fracturing foams. At ambient and elevated temperatures, the combination of SNP and ionic surfactant leads to higher foam stability and foamability, compared to that of SNP and non-ionic surfactant. At sufficient surfactant concentrations, the electrostatic attraction between SNP and cationic surfactant results in a higher half-life, higher apparent viscosity and greater proppant-carrying capacity when compared with the electrostatic repulsion of the SNP-anionic surfactant system. The aggregation behaviour of SNP is promoted by either interacting with the oppositely charged surfactants or increasing the temperature and/or salinity. It is found that the SNP aggregates can either have positive or negative influences on the foams' properties, depending on their size and location of accumulation. The simulation results show that foams' stability, rheology and proppant suspension capacity are directly proportional to the propped area, fracture conductivity and well productivity. In the simulated tight gas reservoir models, the fracturing performance of SNP-surfactant-stabilized foams is significantly greater than that of the benchmark slickwater frac case. The research presents remarkable insights into the synergistic interactions between surfactants and nanoparticles. Furthermore, it provides practical guidelines for designing an optimal nanoparticle-surfactant mixture to stabilize and enhance the properties of fracturing foams at high-temperature and high salinity reservoir conditions.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering, 202

The impact of employer branding on job application intention: Evidence from business undergraduates in Vietnam

This study aims to figure out the impact of employer branding perception on job application intention of business undergraduates in three main provinces of Southeast Vietnam, including Binh Duong, Dong Nai, and Ho Chi Minh City. The result shows that Task Attractiveness, Payment Attractiveness, and Working Atmosphere positively affect business undergraduates’ job application intention. However, our findings also show that the participants do not put a lot of attention on the Work-life Comfort factor and the Career Opportunities factor

Online Load Balancing for Network Functions Virtualization

Network Functions Virtualization (NFV) aims to support service providers to deploy various services in a more agile and cost-effective way. However, the softwarization and cloudification of network functions can result in severe congestion and low network performance. In this paper, we propose a solution to address this issue. We analyze and solve the online load balancing problem using multipath routing in NFV to optimize network performance in response to the dynamic changes of user demands. In particular, we first formulate the optimization problem of load balancing as a mixed integer linear program for achieving the optimal solution. We then develop the ORBIT algorithm that solves the online load balancing problem. The performance guarantee of ORBIT is analytically proved in comparison with the optimal offline solution. The experiment results on real-world datasets show that ORBIT performs very well for distributing traffic of each service demand across multipaths without knowledge of future demands, especially under high-load conditions

A conceptual framework of virtual team effectiveness from the socio-technical perspective

In the era of globalization and technologization, virtual teamwork has become a routine part of professional activity in the software industry and other industries. Understanding virtual team effectiveness helps the management to improve the overall effectiveness of organizations. In this paper, we conduct a literature review of team research to set up a conceptual framework of virtual team effectiveness based on the socio-technical perspective and Inputs-Mediators- Outputs-Inputs model. Our framework includes some salient inputs, mediators and outputs of virtual team life-cycle; specifically, technology readiness and intention to explore are two technical antecedents; team learning and transactive memory system are two social antecedents; and team performance is a socio-technical output representing virtual team effectiveness. After that, a 27-item measuring instrument of aforesaid concepts is proposed after a qualitative survey of 19 virtual team leaders and a quantitative survey of 151 virtual team members from 19 companies locating in Vietnam. The results are references for those interested in improving virtual team effectiveness

Ecological Engineering and Restoration of Eroded Muddy Coasts in South East Asia: Knowledge Gaps and Recommendations

Ecological engineering (EE) was employed for developing strategies for stabilizing eroded muddy coasts (EMCs). However, there was a limited analysis of these EE strategies with respect to design, performance, and lessons learned. This study employed a critical review for addressing the limitations. There were four EE models designed with different restoration interventions for stabilizing EMCs. The models using active interventions have not been cost-effective in controlling erosion because the interventions failed to achieve their goals or were costly and unnecessary. Of the two passive intervention models, the one with structures constructed from onshore proved to be more cost-effective in terms of construction costs, the survival rate of transplanted seedlings, and levels of sea mud accumulation. Interventions with adequate consideration of the muddy coastal ecological processes and the ecological reasoning for the positioning of these interventions play a crucial role in stabilizing EMCs. A passive restoration model using gradually expanded interventions should be promoted in order to ensure sustainable management of EMCs in the future

Vietnam geographical exploitation under the United Nations Convention on the Law of the Sea in 1982 (UNCLOS 1982)

As an active member of the United Nations Convention on the Law of the Sea - UNCLOS, Vietnam has completed 3 Reports on the Limits of the Continental Shelf and has submitted two of them to the Commission on the Limits of the Continental Shelf - CLCS, before the deadline 13-5-2009. Those are: (1) Outer Limits of the Vietnam’s Extended Continental Shelf: North Area (VNM-N); (2) Outer Limits of the Vietnam’s Extended Continental Shelf: Middle Area (VNM-M) and (3) Vietnam - Malaysia Joint Continental Shelf Submission. The VNM-M has not yet been submitted but it was mentioned to the CLCS and will be submitted in the appropriate time.Vietnam’s submissions were highly appreciated by CLCS; although the CLCS has not yet organized a special sub-committee to look at our reports, the secretariat of CLCS has already posted the executive reports of our submissions, with our principle claims on the continental shelf, on the website of the CLCS since May 2009. This paper presents shortly the UNCLOS and its application in Vietnam case

Knowledge sharing in virtual teams: A research in information technology companies in Vietnam

Nowadays, virtual teams bring both benefits and drawbacks to companies, especially to information technology companies. Improving virtual team performance is a requisite to speed up the development of information technology companies. This article conducts quantitative research on virtual team members in Vietnam’s information technology companies to investigate the relationships between social capital, risk of opportunistic behaviors, knowledge sharing, and team performance in the situation of virtual teams. The study uses SPSS and AMOS to analyze data collected from 268 valid samples. We find out a reliable 15-variable scale which can be used to measure structural social capital, cognitive social capital, rational social capital, risk of opportunistic behaviors, knowledge sharing and virtual team performance. The results show the positive effects of structural social capital and cognitive social capital on knowledge sharing and virtual team performance. The findings also reveal the negative effects of risk of opportunistic behaviors on knowledge sharing and virtual team performance and a positive correlation between knowledge sharing and virtual team performance. This article can be used as a reference for managers to build solutions for improving virtual team performance in information technology companies in Vietnam

Risk factors for cannula-associated arterial thrombosis following extracorporeal membrane oxygenation support: a retrospective study

Background Hemostatic dysfunction during extracorporeal membrane oxygenation (ECMO) due to blood-circuit interaction and the consequences of shear stress imposed by flow rates lead to rapid coagulation cascade and thrombus formation in the ECMO system and blood vessels. We aimed to identify the incidence and risk factors for cannula-associated arterial thrombosis (CaAT) post-decannulation. Methods A retrospective study of patients undergoing arterial cannula removal following ECMO was performed. We evaluated the incidence of CaAT and compared the characteristics, ECMO machine parameters, cannula sizes, number of blood products transfused during ECMO, and daily hemostasis parameters in patients with and without CaAT. Multivariate analysis identified the risk factors for CaAT. Results Forty-seven patients requiring venoarterial ECMO (VA-ECMO) or hybrid methods were recruited for thrombosis screening. The median Sequential Organ Failure Assessment score was 11 (interquartile range, 8–13). CaAT occurred in 29 patients (61.7%), with thrombosis in the superficial femoral artery accounting for 51.7% of cases. The rate of limb ischemia complications in the CaAT group was 17.2%. Multivariate analysis determined that the ECMO flow rate–body surface area (BSA) ratio (100 ml/min/m2) was an independent factor for CaAT, with an odds ratio of 0.79 (95% confidence interval, 0.66–0.95; P=0.014). Conclusions We found that the incidence of CaAT was 61.7% following successful decannulation from VA-ECMO or hybrid modes, and the ECMO flow rate–BSA ratio was an independent risk factor for CaAT. We suggest screening for arterial thrombosis following VA-ECMO, and further research is needed to determine the risks and benefits of such screening

TextANIMAR: Text-based 3D Animal Fine-Grained Retrieval

3D object retrieval is an important yet challenging task, which has drawn more and more attention in recent years. While existing approaches have made strides in addressing this issue, they are often limited to restricted settings such as image and sketch queries, which are often unfriendly interactions for common users. In order to overcome these limitations, this paper presents a novel SHREC challenge track focusing on text-based fine-grained retrieval of 3D animal models. Unlike previous SHREC challenge tracks, the proposed task is considerably more challenging, requiring participants to develop innovative approaches to tackle the problem of text-based retrieval. Despite the increased difficulty, we believe that this task has the potential to drive useful applications in practice and facilitate more intuitive interactions with 3D objects. Five groups participated in our competition, submitting a total of 114 runs. While the results obtained in our competition are satisfactory, we note that the challenges presented by this task are far from being fully solved. As such, we provide insights into potential areas for future research and improvements. We believe that we can help push the boundaries of 3D object retrieval and facilitate more user-friendly interactions via vision-language technologies.Comment: arXiv admin note: text overlap with arXiv:2304.0573

A Comprehensive Survey of Enabling and Emerging Technologies for Social Distancing—Part II: Emerging Technologies and Open Issues

This two-part paper aims to provide a comprehensive survey on how emerging technologies, e.g., wireless and networking, artificial intelligence (AI) can enable, encourage, and even enforce social distancing practice. In Part I, an extensive background of social distancing is provided, and enabling wireless technologies are thoroughly surveyed. In this Part II, emerging technologies such as machine learning, computer vision, thermal, ultrasound, etc., are introduced. These technologies open many new solutions and directions to deal with problems in social distancing, e.g., symptom prediction, detection and monitoring quarantined people, and contact tracing. Finally, we discuss open issues and challenges (e.g., privacy-preserving, scheduling, and incentive mechanisms) in implementing social distancing in practice. As an example, instead of reacting with ad-hoc responses to COVID-19-like pandemics in the future, smart infrastructures (e.g., next-generation wireless systems like 6G, smart home/building, smart city, intelligent transportation systems) should incorporate a pandemic mode in their standard architectures/designs