دانلود و نمایش مقالات مرتبط با System dynamics::صفحه 1
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نتیجه جستجو - System dynamics

تعداد مقالات یافته شده: 28
ردیف عنوان نوع
1 Generation of Accessible Sets in the Dynamical Modeling of Quantum Network Systems
تولید مجموعه‌های قابل دسترس در مدل‌سازی دینامیکی سیستم‌های شبکه کوانتومی-2022
In this article, we consider the dynamical modeling of a class of quantum network systems consisting of qubits, where information extraction is allowed by performing measurement on several selected qubits of the system. For a variety of applications, a state space model is a useful approach to modeling the system dynamics. To construct a state space model for a quantum network system, the major task is to find an accessible set containing all of the operators coupled to the measurement operators. This article focuses on the generation of a proper accessible set for a given system and measurement scheme. We provide analytic results on simplifying the process of generating accessible sets for systems with a time-independent Hamiltonian. Since the order of elements in the accessible set determines the form of state space matrices, guidance is provided to effectively arrange the ordering of elements in the state vector. Defining a system state according to the accessible set, one can develop a state space model with a special pattern inherited from the system structure. As a demonstration, we specifically consider a typical 1-D-chain system with several common measurements and employ the proposed method to determine its accessible set.
Index Terms: Accessible set | dynamical modeling | quantum network system | quantum system.
مقاله انگلیسی
2 Prediction of forest parameters and carbon accounting under different fire regimes in Miombo woodlands, Niassa Special Reserve, Northern Mozambique
پیش بینی پارامترهای جنگلی و حسابداری کربن تحت رژیم های مختلف آتش سوزی در جنگل های میومبو، رزرو ویژه NIASSA، شمال موزامبیک-2021
Miombo woodlands are the most extensive dry forest type in southern Africa, covering ca. 1.9 million km2 across seven countries. Fire is a key ecosystem process that has structured miombo for the last 200,000 years. However, how fires affect the ecosystems functioning is not well understood. In this study, we used the individual-based forest model called FORMIND to analyze the carbon balance in the miombo woodlands of Niassa Special Reserve (NSR), northern Mozambique. The 42.000 km2 NSR represents the most important conservation area in Mozambique (~31% of the total conservation area in the country) and of miombo woodlands worldwide. Longterm inventory data from 2004 to 2019 for NSR were used to calibrate FORMIND. The primary ecosystem processes of this model are tree growth, mortality, regeneration, and competition. Fire is set as one of the main factors that affect these processes, after the woodland reaches an equilibrium at 200 years of age. We also calculated the Net Present Value (NPV) of carbon credits resulting from altering the fire regime (e.g., reducing or eliminating fires). The FORMIND model successfully reproduced important characteristics of the woodlands (aboveground biomass, stem size distribution and basal area). NPV estimates of above-ground woody biomass carbon stocks were highly dependent on the woodland age. The maximum NPV estimates were generated for a 30-year project starting with 200 year old woodlands (the current forest age) at 192–1339 USD based on a realistic range of carbon values (i.e., 3–20 USD MgCO2e− 1). While fire plays an important role in miombo woodlands by reducing stock and changing species composition, its effects on the capacity of the woodland to mitigate the effects of climate change varies depending on the age of stands. Our results show that FORMIND model reliably reproduce the field inventory data, thus can be used to improve carbon accounting standards. We recommend the development of a fire management system to sustain the miombo woodlands of NSR for multiple reasons. NSR is a globally significant protected area, but perhaps more importantly it could become a regional example for how to improve miombo woodland management. Given that miombo woodlands provide a myriad of ecosystem services to rural Africans, investing in improving fire management could increase the benefits to local communities. Altering fire regimes could improve habitat quality and promote greater resilience to climate change while sequestering carbon. In addition, local employment opportunities in fire management could be created via carbon financing from a carbon project. However, much more outreach and education will be needed to local and national stakeholders for fire management to be perceived more positively and realize the potential to generate multiple benefits for nature and people.
keywords: مدل GAP Formind | دینامیک اکوسیستم | حسابداری کربن | مدیریت آتش نشانی | خط مشی آتش | FORMIND gap model | Ecosystem dynamics | Carbon accounting | Fire management | Fire policy
مقاله انگلیسی
3 Offsite construction supply chain strategies for matching affordable rental housing demand: A system dynamics approach
استراتژی های زنجیره تأمین ساخت و ساز خارج از ساختمان برای مطابقت با تقاضای مسکن اجاره ای ارزان قیمت: رویکرد پویایی سیستم-2021
Australian housing affordability is influenced by both housing supply and demand factors. These factors include lengthy construction and planning process. The affordability crisis affects the housing rental sector, which accommodates more than 20 % of Australian household. This research developed a system dynamics model to simulate demography-linked affordable rental housing demand and supply in South East Queensland (SEQ). A Prefabricated Offsite Construction (OSC) housing supply strategy is compared with a traditional building approach (BAU) to investigate the effectiveness of OSC techniques to reduce informational asymmetries during development planning stages to deliver better affordable rental housing is linked to housing needs in SEQ. The model focuses on demographic groups housing demand of one, two- and three-bedroom apartment units and examines how reductions in the development process, through OSC methods, influence the efficiency of Government supported affordable rental housing supply schemes. Overall, the study finds that reduced planning and construction timeframes through OSC methods may improve demography-linked rental housing supply by approximately 6.6 % overall compared to BAU in SEQ. For 1,2- and 3-bedroom apartment demand, OSC strategies are expected to improve supply efficiency by 8.7 %, 8.4 % and 9.2 %, respectively. Optimal OSC strategies were assessed and found that flexibility in development sizes have an outsized positive effect. The study has implications for Government supported affordable rental housing strategies, including the build to rent sector.
Keywords: Offsite construction | Sustainable development | Social resilience | Affordable housing policy | Urban systems modelling | System dynamics | Prefabrication
مقاله انگلیسی
4 Circular economy for phosphorus supply chain and its impact on social sustainable development goals
اقتصاد مدور برای زنجیره تأمین فسفر و تأثیر آن بر اهداف توسعه پایدار اجتماعی-2021
To be able to grow crops, we have interfered with Earths reserves of one of top three essential elements, phosphorus (P), as to which we face a problem related to its high consumption compared to available resources. This forces us to follow the alternative of closing the phosphorus loop from a circular economy perspective. However, there is a lack of research on regional and global social sustainability in this area, as emphasized in the United Nations Agenda 2030 goals for sustainable development. In this paper, we address social challenges involved in global phosphorus supply chain, such as eradicating poverty, child labor and malnutrition; promoting gender equality; providing decent work and economic growth; maintaining sustainable water use; and achieving food security. Our research is driven by the question of whether the circular economy aims to direct phosphorus management towards tackling social issues associated with its supply chain. We use system dynamics modelling by combining the concept of material flow analysis and social life cycle assessment. Detailed analysis at regional and global levels indicates a paradoxical social impact of phosphorus circular model. This reflects the multiple stakeholders involved, and the regional interactions with phosphorus circular economy transitions. Improvements can be demonstrated in reducing poverty and providing safer work environment in many regions, e.g., Western Asia (93%), New Zealand, Central Asia, and Europe (44–61%), while achieving employment targets is limited in Northern and Eastern Europe. Circular model fails to promote gender equality, it also exacerbates exploitative child work problem for the Caribbean and most Africa. It provides sufficient nutrition to North America, Australia/New Zealand, and Northern Europe. It achieves water use targets in several regions with 53% savings worldwide. Finally, circular model contributes to P efficiency (average balance of 1.21 kgP/ha) and strengthens P security within most regions with an average of 64%.
Keywords: Critical materials | Phosphorus | Social sustainability | Circular economy | Dynamic modelling
مقاله انگلیسی
5 Nonlinear analysis and active management of production-distribution in nonlinear supply chain model using sliding mode control theory
تحلیل غیرخطی و مدیریت فعال تولید-توزیع در مدل غیر خطی زنجیره تامین با استفاده از تئوری کنترل حالت کشویی-2021
This paper deals with system dynamics approach for dynamical behaviors and control synthesis of supply chain system by utilizing three-stage production-distribution model. The presented approach offers systematic tools for determining fundamental relationships between multi-echelons in the supply chain dynamics by using eigenvalues, bifurcation, and time history investigation. By exploring system dynamics on time series analysis, it is found that system performance has suffered severely from the bullwhip effect under impacts of model uncertainties and perturbed demand. The novel fractional-order sliding mode control algorithm has been presented based on adaptation mechanism, ensuring that the shipment flows are robustly stable in supply chain networks against disruptions. This is a smarter way of getting sufficient strength to sustain existing competitive market for mitigating the risks and improving the supply chain performance. The system stability has been thoroughly analyzed by using Routh-Hurwitz criterion and Lyapunov theory. Extensive numerical simulations have been conducted to obtain insights into the system behaviors and to validate effectiveness of active control policies by matching the shipment sent to customer demand, ensuring supply chains resilience. Finally, it is found that the presented approach can help decision-makers develop more efficient supply chain management system against severe market disruptions.
Keywords: System dynamics | Supply chain management | Production-distribution model | Fractional order | Sliding mode control | Adaptive law
مقاله انگلیسی
6 Dynamic simulation modelling of software requirements change management system
مدل سازی شبیه سازی پویا سیستم مدیریت تغییر نیازمندی های نرم افزاری-2021
Changes in the Software requirements, technological advances require flexibility in software system develop- ment. Unexpected changes and mistakes cause difficulties. They effectively manage destructive changes, rework, and errors; project managers need to consider dynamic behavior loops of feedback on lead delays and distur- bances. System Dynamics (SD) modeling methods have been used in the last few decades to meet this demand for analytical and project performance improvement. The SD model is used to improve the simulated change management policy for the Iranian project in the project’s planning and petrochemical industry. Dynamic simulations of the SD model. The results show that effective Knowledge Management (KM) is a crucial control factor for the project’s mechanically essential controls. Therefore, the proposal on the Knowledge Management aspect and attempts are to improve the manufacturing industry model. Effective formulation of dynamic simulation models project change management policy, time, consider Cost, quality, resources, and financial indicators. This model, such as financing, outsourcing activities, adjustment of the schedule, labor management, etc., to compare the alternative change management strategy in terms of the project’s performance indicators to enable the decision-makers.
keywords: مدیریت دانش | پویایی سیستم (SD) | هزینه | کیفیت | منابع | Knowledge management (km) | System dynamics (sd) | Cost | quality | resources
مقاله انگلیسی
7 The impacts of inventory in transfer pricing and net income: Differences between traditional accounting and throughput accounting
اثرات موجودی در قیمت گذاری انتقال و درآمد خالص: تفاوت بین حسابداری سنتی و حسابداری عملیاتی-2021
This research proposes the Theory of Constraints (TOC) throughput accounting (TA) as an alternative management control mechanism in an international transfer pricing setting. We compare TA with the traditional accounting method and demonstrate that the traditional method underestimate factors as demand variation and inventories, which affects decisions, such as moving production to an offshore plant. A detailed system dynamics model is built to simulate the production process in an offshore supply chain to compare the methods. The study aims to fill a gap in the management accounting studies and contribute to the understanding of international transfer pricing and their management controls, exploring more than just the tax savings, which are usually considered isolated from operational factors for supply chain (SC) offshoring decisions. Furthermore, we conduct a brief literature review, present the model and discuss the results. It has been observed that inventory levels are an important part of accounting, offshored supply chains, and transfer pricing. Traditional cost and accounting methods favour higher inventory levels, and they can overestimate net income results up to 70% e especially in higher demand variation scenarios e when compared to the throughput accounting.
keywords: انتقال قیمت گذاری | تئوری محدودیت ها | زنجیره تامین بین المللی | خفه کن | Transfer pricing | Theory of constraints | International supply chain | Offshoring
مقاله انگلیسی
8 The development of complex and controversial innovations. Genetically modified mosquitoes for malaria eradication
توسعه نوآوری های پیچیده و بحث برانگیز. پشه های اصلاح شده ژنتیکی برای ریشه کن کردن مالاریا-2020
When there is significant uncertainty in an innovation project, research literature suggests that strictly sequencing actions and stages may not be an appropriate mode of project management. We use a longitudinal process approach and qualitative system dynamics modelling to study the development of genetically modified (GM) mosquitoes for malaria eradication in an African country. Our data were collected in real time, from early scientific research to deployment of the first prototype mosquitoes in the field. The gene drive technology for modifying the mosquitoes is highly complex and controversial due to risks associated with its characteristics as a living, self-replicating technology. We show that in this case the innovation journey is linear and highly structured, but also embedded within a wider system of adoption that displays emergent behaviour. Although the need to control risks associated with the technology imposes a linearity to the NPD process, there are possibilities for deviation from a more structured sequence of stages. This arises from the effects of feedback loops in the wider system of evidence creation and learning at the population and governance levels, which cumulatively impact on acceptance of the innovation. The NPD and adoption processes are therefore closely intertwined, meaning that the endpoint for R&D and beginning of mainstream adoption and diffusion are unclear. A key challenge for those responsible for NPD and its regulation is to plan for the adoption of the technology while simultaneously conducting its scientific and technical development.
Keywords: New product development | Adoption | Genetically modified mosquitoes | Living technology | Gene drive | Malaria
مقاله انگلیسی
9 Low carbon building performance in the construction industry: A multi-method approach of project management operations and building energy use applied in a UK public office building
کارایی ساخت کربن کم در صنعت تولید : یک رویکرد چند روش از عملیات مدیریت پروژه و استفاده از انرژی مصرفی ساختمان که در ساختمان اداری عمومی انگلیس اعمال می شود-2020
The “performance gap”in the United Kingdom construction industry is a persistent problem as new building development projects underperform more often than not. The “performance gap”is partially attributed to the number of stages involved in building project development and the coordination diffi- culties of partners with different incentives. The project outcome is important for energy consumption, carbon emissions and occupant well-being. Thus, it is important to study the project management pro- cess in terms of the standard time, cost and quality parameters, but also in terms of project partner incentives and coordination, and the subsequent energy performance and resultant indoor environmental conditions. A system dynamics model of project management processes is developed to explore the im- plications of partner coordination for building quality. The system dynamics model is coupled to a build- ing performance simulation model to explore building energy consumption and Indoor Environmental Quality, and apply this on a recent building project case study. Results show that greater project partner alignment can reduce annual energy consumption up to 12% and CO 2 emissions up to 37%, with greater emphasis in the design stage of the project subject to resource availability. The trade-offs involved on value appropriation are considered and discussion of results points to possible ways for improvement.
Keywords: Energy consumption | Simulation | Low carbon | Building performance | System dynamics
مقاله انگلیسی
10 Identifying safety archetypes of construction workers using system dynamics and content analysis
شناسایی الگوی اصلی ایمنی کارگران ساختمانی با استفاده از پویایی سیستم و تحلیل محتوا-2020
Construction accidents have unique features on the surface, while further investigation often reveals common underlying systemic patterns that lead to accidents. By identifying these patterns, organizations can better understand past accidents, monitor risk, and reduce the likelihood of future accidents. Further, construction project management is such a complex effort due to the unique, dynamic, and temporary nature of the construction industry. Furthermore, there is lack of research on exploring the systematic patterns responsible for occurrence of accidents. To address this gap in knowledge, this paper aims to better understand the dynamic complexity of construction safety by identifying behavioral patterns of workers that recur in construction projects continuously. Content analysis and ground theory method (GTM) were adopted for this research. In total, 100 papers were reviewed to explore the influential factors affecting the safety in construction projects. Furthermore, 20 interviews were conducted with experts in the field of construction health and safety. The results showed that there are four archetypes of construction workers: (1) blame on workers, (2) construction delay, (3) incentive programs, and (4) subcontractors’ financial status. The identified archetypes have been illustrated at different steps including the dynamic theory, behavior over time, and the leverage point to show how to manage the archetype. The developed archetypes could be useful for decision-makers and help them be aware of the longterm effects of their decisions in the projects. They also provide systemic vision for project managers helping them understand the dynamic complexity of construction safety management.
Keywords: Construction management | Safety | Systems thinking | Content analysis | System dynamics | Archetypes | Worker
مقاله انگلیسی
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