scholarly journals Comparison of Alternative Pulpwood Inventory Strategies and Machine Systems at a Log-Yard Using Simulations

Forests ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 373
Author(s):  
Kalvis Kons ◽  
Pedro La Hera ◽  
Dan Bergström
Keyword(s):  
Discrete Event ◽  
Work Load ◽  
Storage Site ◽  
Work Time ◽  
Machine System ◽  
Buffer Storage ◽  
Storage Area ◽  
Inventory Strategy ◽  
Machine Systems ◽  
The Impact

The rising throughput of log-yards imposes new constraints on existing equipment and increases the complexity of delivering an optimal and uninterrupted supply of pulpwood to pulp mills. To find ways of addressing these problems by reducing log cycle times, this work uses a discrete-event mathematics model to simulate operations at a log-yard and study the impact of three different log-yard inventory strategies and two alternative machine systems for log transportation between main log-yard and buffer storage. The yard’s existing inventory strategy of last load in and first out limits access to older logs at the main storage site. By allocating space for 89,000 m3 and 99,000 m3 of pulpwood at the buffer storage it is possible to keep the log cycle time at the main storage to a maximum of 12 and 6 months. Additionally, the use of an alternative log transportation machine system comprising a material handler with a trailer increased the work time capacity utilization relative to the yard’s current machine system of two shuttle trucks and a material handler for transporting logs between the main and buffer storage areas. Compared to the currently-used last in first out inventory strategy and purposely emptying the main storage area once or twice per year did reduce the total work time of both machine systems by 14% and 30%. Consequently, the volume delivered from the buffer to the log-yard decreased on average by 17% and 37% when emptying the main storage area once and twice per year. Even with reduced work time when emptying the main storage area, both machine systems could fulfil given work load for transporting logs from the buffer storage to the main log-yard without interrupting operations of the log-yard.

Predicting Graceful Extensibility of Human-Machine Systems: A New Analysis Method for Evaluating Extensibility Plots to Anticipate Distributed System Performance

2020 ◽  
Vol 64 (1) ◽  
pp. 313-318
Author(s):  
Dane A. Morey ◽  
Jesse M. Marquisee ◽  
Ryan C. Gifford ◽  
Morgan C. Fitzgerald ◽  
Michael F. Rayo
Keyword(s):  
Artificial Intelligence ◽  
Distributed System ◽  
System Performance ◽  
Healthcare Setting ◽  
Evaluation Methods ◽  
Performance Data ◽  
Analysis Method ◽  
Machine System ◽  
Machine Systems

With all of the research and investment dedicated to artificial intelligence and other automation technologies, there is a paucity of evaluation methods for how these technologies integrate into effective joint human-machine teams. Current evaluation methods, which largely were designed to measure performance of discrete representative tasks, provide little information about how the system will perform when operating outside the bounds of the evaluation. We are exploring a method of generating Extensibility Plots, which predicts the ability of the human-machine system to respond to classes of challenges at intensities both within and outside of what was tested. In this paper we test and explore the method, using performance data collected from a healthcare setting in which a machine and nurse jointly detect signs of patient decompensation. We explore the validity and usefulness of these curves to predict the graceful extensibility of the system.

scholarly journals Balancing scarce hospital resources during the COVID-19 pandemic using discrete-event simulation

2021 ◽  
Author(s):  
G.J. Melman ◽  
A.K. Parlikad ◽  
E.A.B. Cameron
Keyword(s):  
Resource Allocation ◽  
Discrete Event Simulation ◽  
Elective Surgery ◽  
Discrete Event ◽  
Specific Patient ◽  
Event Simulation ◽  
The Impact ◽  
Allocation Decisions ◽  
Allocation Strategies ◽  
Resource Allocation Decisions

AbstractCOVID-19 has disrupted healthcare operations and resulted in large-scale cancellations of elective surgery. Hospitals throughout the world made life-altering resource allocation decisions and prioritised the care of COVID-19 patients. Without effective models to evaluate resource allocation strategies encompassing COVID-19 and non-COVID-19 care, hospitals face the risk of making sub-optimal local resource allocation decisions. A discrete-event-simulation model is proposed in this paper to describe COVID-19, elective surgery, and emergency surgery patient flows. COVID-19-specific patient flows and a surgical patient flow network were constructed based on data of 475 COVID-19 patients and 28,831 non-COVID-19 patients in Addenbrooke’s hospital in the UK. The model enabled the evaluation of three resource allocation strategies, for two COVID-19 wave scenarios: proactive cancellation of elective surgery, reactive cancellation of elective surgery, and ring-fencing operating theatre capacity. The results suggest that a ring-fencing strategy outperforms the other strategies, regardless of the COVID-19 scenario, in terms of total direct deaths and the number of surgeries performed. However, this does come at the cost of 50% more critical care rejections. In terms of aggregate hospital performance, a reactive cancellation strategy prioritising COVID-19 is no longer favourable if more than 7.3% of elective surgeries can be considered life-saving. Additionally, the model demonstrates the impact of timely hospital preparation and staff availability, on the ability to treat patients during a pandemic. The model can aid hospitals worldwide during pandemics and disasters, to evaluate their resource allocation strategies and identify the effect of redefining the prioritisation of patients.

scholarly journals Potentials of possible machine systems for directly loading logs in cut-to-length harvesting

2012 ◽  
Vol 42 (5) ◽  
pp. 970-985 ◽  
Author(s):  
Ola Ringdahl ◽  
Thomas Hellström ◽  
Ola Lindroos
Keyword(s):  
Fuel Consumption ◽  
Waiting Times ◽  
Discrete Event ◽  
Lead Times ◽  
Event Simulation ◽  
Variable Environments ◽  
Landing Sites ◽  
Machine Systems ◽  
Stand Conditions ◽  
Key Innovations

In conventional mechanized cut-to-length systems, a harvester fells and cuts trees into logs that are stored on the ground until a forwarder picks them up and carries them to landing sites. A proposed improvement is to place logs directly into the load spaces of transporting machines as they are cut. Such integrated loading could result in cost reductions, shorter lead times from stump to landing, and lower fuel consumption. However, it might also create waiting times for the machines involved, whereas multifunctional machines are likely to be expensive. Thus, it is important to analyze whether or not the advantages of any changes outweigh the disadvantages. The conventional system was compared with four potential systems, including two with autonomous forwarders, using discrete-event simulation with stochastic elements in which harvests of more than 1000 final felling stands (containing in total 1.6 million m3) were simulated 35 times per system. The results indicate that harwarders have substantial potential (less expensive on ≥80% of the volume and fuel consumption decreased by ≥18%) and may become competitive if key innovations are developed. Systems with cooperating machines have considerably less potential, limited to very specific stand conditions. The results conform with expected difficulties in integrating processing and transporting machines’ work in variable environments.

scholarly journals Assessing asset monitoring levels for maintenance operations

2015 ◽  
Vol 26 (5) ◽  
pp. 632-659 ◽  
Author(s):  
Abdullah A Alabdulkarim ◽  
Peter Ball ◽  
Ashutosh Tiwari
Keyword(s):  
Asset Management ◽  
Business Models ◽  
Discrete Event ◽  
Dynamic Modelling ◽  
Simulation Models ◽  
Content Type ◽  
Event Simulation ◽  
Product Service ◽  
Asset Monitoring ◽  
The Impact

Purpose – Asset management has recently gained significance due to emerging business models such as Product Service Systems where the sale of asset use, rather than the sale of the asset itself, is applied. This leaves the responsibility of the maintenance tasks to fall on the shoulders of the manufacturer/supplier to provide high asset availability. The use of asset monitoring assists in providing high availability but the level of monitoring and maintenance needs to be assessed for cost effectiveness. There is a lack of available tools and understanding of their value in assessing monitoring levels. The paper aims to discuss these issues. Design/methodology/approach – This research aims to develop a dynamic modelling approach using Discrete Event Simulation (DES) to assess such maintenance systems in order to provide a better understanding of the behaviour of complex maintenance operations. Interviews were conducted and literature was analysed to gather modelling requirements. Generic models were created, followed by simulation models, to examine how maintenance operation systems behave regarding different levels of asset monitoring. Findings – This research indicates that DES discerns varying levels of complexity of maintenance operations but that more sophisticated asset monitoring levels will not necessarily result in a higher asset performance. The paper shows that it is possible to assess the impact of monitoring levels as well as make other changes to system operation that may be more or less effective. Practical implications – The proposed tool supports the maintenance operations decision makers to select the appropriate asset monitoring level that suits their operational needs. Originality/value – A novel DES approach was developed to assess asset monitoring levels for maintenance operations. In applying this quantitative approach, it was demonstrated that higher asset monitoring levels do not necessarily result in higher asset availability. The work provides a means of evaluating the constraints in the system that an asset is part of rather than focusing on the asset in isolation.

The impact of commonly used air filters in eliminating the exposure to secondhand smoke constituents

2015 ◽  
Vol 17 (3) ◽  
pp. 543-551
Author(s):  
Chris A. Pritsos ◽  
Thivanka Muthumalage
Keyword(s):  
Experimental Design ◽  
Environmental Tobacco Smoke ◽  
Tobacco Smoke ◽  
Secondhand Smoke ◽  
Air Filters ◽  
Machine System ◽  
The Impact ◽  
Exposure To Secondhand Smoke

The use of microchip controlled TE-10 smoke machine system with 3R4F research cigarettes as a part of the experimental design in order to create an atmosphere with environmental tobacco smoke constituents.

scholarly journals The Impact of an Application of TelerehabilitationTechnology on Caregiver Burden

2009 ◽  
Vol 1 (1) ◽  
pp. 3-8 ◽  
Author(s):  
Lyn R. Tindall ◽  
Ruth A. Huebner
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Caregiver Burden ◽  
Speech Therapy ◽  
Structured Interview ◽  
Elderly Persons ◽  
Work Time ◽  
Financial Obligation ◽  
The Impact ◽  
Therapy Protocol

The objective of this research was to assess the effects of an application of telerehabilitation reducing time and financial obligation on caregiver burden among eleven caregivers of elderly persons with Parkinson’s disease. Clients (care receivers) participated in speech therapy delivered via videophones in their homes; the protocol required 16 treatments delivered four times a week for four weeks. At the conclusion of treatment, caregivers completed a structured interview about the impact of telerehabilitation on time and financial aspects of the burden of care. On average, this speech therapy protocol delivered by videophones saved 48 hours of time, more than 92 hours of work time, and $1024 for each caregiver. Savings were significant and previous research demonstrated nearly equal outcomes using the videophone delivery method. Implications for practice and research are discussed. Keywords: Telerehabilitation, Speech Therapy, Parkinson’s Disease.  

scholarly journals The contribution of reduced COVID-19 test time in controlling the spread of the disease: A simulation-based approach

2022 ◽  
Vol 12 (2) ◽  
Author(s):  
Youness Frichi ◽  
Abderrahmane Ben Kacem ◽  
Fouad Jawab ◽  
Said Boutahari ◽  
Oualid Kamach ◽  
...  
Keyword(s):  
Discrete Event ◽  
Mass Scale ◽  
Test Time ◽  
Test Duration ◽  
Accurate Identification ◽  
Event Simulation ◽  
Simulation Results ◽  
Precautionary Measures ◽  
Novel Coronavirus ◽  
The Impact

The novel coronavirus COVID-19 has known a large spread over the globe threatening human health. Recommendations from WHO and specialists insist on testing on a mass scale. However, health systems do not have enough resources. The current process requires the isolation of testees in the hospitals’ isolation rooms for several hours until the test results are revealed, limiting hospitals’ capacities to test large numbers of cases. The aim of this paper was to estimate the impact of reducing the COVID-19 test time on controlling the pandemic spread, through increasing hospitals’ capacities to test on a mass scale. First, a discrete-event simulation was used to model and simulate the COVID-19 testing process in Morocco. Second, a mathematical model was developed to demonstrate the effect of accurate identification of infected cases on controlling the disease’s spread. Simulation results showed that hospitals’ testing capacities could be increased six times if the test duration fell from 10 hours to 10 minutes. The reduction of test time would increase testing capacities, which help to identify all the infected cases. In contrast, the simulation results indicated that if the infected population is not accurately identified and no precautionary measures are taken, the virus will continue to spread until it reaches the total population. Reducing test time is a vital component of the response to the COVID-19 pandemic. It is essential for the effective implementation of policies to contain the virus.

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