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Academics using AIMMS

A dedicated space for academics and researchers to connect, ask questions, share research insights, and explore academic opportunities with AIMMS.

207 Topics
Aanand
AIMMSian
AanandAIMMSian
published in Modeling for Impact
Study 1Knowledge Base

Study 1: Anticipate Best- and Worst-Case Operations Scenarios This study can help you understand exposure in your supply chain. Impact – Prolonged shutdowns will have both financial and operation implications, which are often very difficult to realize due to the complexity and far-reaching nature of supply chains.  Action – Scenario planning is the key to understanding the many repercussions of sudden changes in demand and operations. Multiple best/worst case scenarios should be run under different demand conditions to study its impact on your supply chain. This can help expose any vulnerabilities in the network and take business a step closer towards preparedness.   How – AIMMS Network Design Navigator allows users to adjust demand for unique customers, locations and products. This means that you can target very specific parts of your demand data and dynamically run different scenarios in those conditions to measure its effect. On top of this, after demand has been adjusted, demand si

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Aanand
AIMMSian
Aanand
AIMMSian
AanandAIMMSian
published in Modeling for Impact
Immediate Supply Chain Actions to Take Amid COVID-19Knowledge Base

There are many impacts of COVID-19 that will be felt by Supply Chains in the coming weeks and months. As advised by McKinsey, in the next 2-4 weeks it is critical for companies to understand the exposure throughout their value chain, take actions to address anticipated shortages and ensure resources requirements to restart.   Supply chain planning tools like AIMMS SC Navigator can be used to directly address many of these impacts and help businesses recover quickly from losses.  We hope that this series of articles gives you some direction - and we welcome your comments and advice from experiences relating to these challenges.   Understand Exposure Study 1: Anticipate Best- and Worst-Case Operations Scenarios Study 2: Inspect Demand Trends   Anticipate Shortages Study 3: Identify Optimal Sourcing Locations   Ensure Resource Requirements Study 4: Create Multiple Plans for Resource Utilization Study 5: Refine Capacity Smoothing Study 6: Accelerate Adoption of Relevant Customer Channels  

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Aanand
AIMMSian
Aanand
AIMMSian
AanandAIMMSian
published in Modeling for Impact
Study 6Knowledge Base

Study 6: Accelerate Adoption of Relevant Customer Channels This study can help you ensure resource requirements in your supply chain. Impact – A very likely scenario is an accelerated adoption of certain customer channels, for instance online grocery. These channels might not be able to bear the increased shift in demand. Action – Relevant customer channels must be prioritized and the resource requirements to fulfill their demand must be studied.  How –AIMMS S&OP Navigator allows users to prioritize their customers to increase the fulfillment in that channel. Although a forced higher fulfillment of one channel might lead to an overall lower margin, understanding the impact on your resources of putting a higher burden on that channel could prove to be invaluable in the long run. Demo –Customer Channel Priority in S&OP Navigator This article is part of the series Immediate Supply Chain Actions to Take Amid COVID-19. 

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Aanand
AIMMSian
chrdttchavan
chrdttchavanNewcomer
asked in Research & AIMMS Questions
Optimization Solvers

Dear All, Looking for a list of solvers (LP/MIP/NLP/quadratic), applications and limitations. Thanks.

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chrdttchavan
Jess Es
Jess EsGrand Master
published in Research & AIMMS Questions
Polaris Optimization Systems: Empowering Decision-making in the Energy SectorInterview

We spoke with Russ Philbrick, founder of Polaris Optimization Systems, about optimization solutions for energy sector customers. Find out how the AIMMS-based engine PSO (Power System Optimizer) helps the power industry make the most of renewable energy.    Can you tell me a little about your background in the energy sector? I started working with Alstom back in 1999 and was responsible for the engines used to plan day-ahead unit commitment and reliability unit commitment. That project was very successful, and even today a number of power markets still run on AIMMS as the core engine, based on that work.   What led you to start Polaris?  In the mid-2000s, I was asked to support efforts to represent what Alstom was doing to support wind integration.  I began to understand that, because of the variability and uncertainty of wind and solar, integration into the power grid presented new planning and operational challenges. With wind and solar, it’s a new kind of uncertainty and variability

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Paul KoutstaalNewcomer
posted in Research & AIMMS Questions
Electricity market modelling in AIMMS

The COMPETES electricity market model   At PBL, the Netherlands Environmental Assessment Agency, AIMMS is used to model the European electricity market. We use this model for outlooks of future electricity market developments and to analyse policy impacts such as the impact of CO2 taxes on electricity generation and prices. COMPETES is a power system optimization tool that seeks to minimize the total power system costs while accounting for the technical constraints of the generation units, transmission constraints between the countries and the generation capacity expansion for conventional technologies. The model covers 28 EU member states and some non-EU countries (i.e., Norway, Switzerland, and the Balkan countries), including a representation of the cross-border transmission network interconnecting these European countries. There are 11 types of fossil-fuel fired power plants as well as nuclear, geothermal, biomass, waste, hydro, wind and solar technologies; unit by unit generation

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Jess Es
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pira1338Explorer
asked in Research & AIMMS Questions
How to start solving with an initial solution

Hi,  I have an initial solution assigned to the two-dimensional variable x(i,j) .  How can I start solving the mathprogram using this initial solution? I did the following steps but I need details about the element parameter which is the second argument  in sendtosolversession?)   Thanks in advance read x from file “sol.txt”; myGMP := GMP::Instance::Generate(MyModel);  SolverSession :=GMP::Instance::CreateSolverSession(myGMP); GMP::Solution::SendToSolverSession(SolverSession, ???)    

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MelikeNewcomer
posted in Research & AIMMS Questions
Precedence Tasks

Hello,I couldnt formulize the precedence relation above in my constraints. Could anyone help me with that? I tried to use the Activities for the tasks but didnt know how to use them with constraintsThanks in advanceMelike

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tobiNewcomer
published in Research & AIMMS Questions
Risk-sensitive planning support for forest enterprises: The YAFO model

“YAFO is a planning-support tool for the development of management plans under uncertainty focusing on the forest enterprise level. Based on existing stand data, the software provides the calculation of management scenarios (felling plans) for single stands that are optimized with respect to financial considerations and ecological constraints. Under these constraints, YAFO predicts timber stocks, harvest amounts and financial returns for each simulation period.”Härtl, Fabian; Hahn, Andreas; Knoke, Thomas (2013): Risk-sensitive planning support for forest enterprises. The YAFO model. In: Computers and Electronics in Agriculture 94, S. 58–70. DOI: 10.1016/j.compag.2013.03.004 Yafo was developed at the Institute of Forest Management (Technical University of Munich) and is continuously driven further to challenge new research questions. We appreciate the free educational version of Aimms to be up-to-date with the newest modelling techniques. So far YAFO enabled new insights in: the

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Jess Es
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Gloria QuintanillaFormer AIMMSian
published in Academic News & Opportunities
Announcing the Winners of the 2019 AIMMS-MOPTA Optimization Modeling CompetitionNews

We are pleased to announce Team ZIB from the Zuse Institute Berlin as the winners of the 11th AIMMS-MOPTA Optimization Modeling Competition. Team ZIB’s solution, report and modeling effort in AIMMS was selected as the most comprehensive among the three finalists at the MOPTA conference banquet, which took place at Lehigh University, Bethelehem on August 15, 2019. AIMMS is excited to continue supporting MOPTA. This year’s problem statement, designed by Boris Defourny (Lehigh University), continued the tradition of an interesting problem with multiple ways to solve it. The participants were asked to solve a packing problem. They were tasked with finding the best solution and recommending alternative solutions that were comparable in packing efficiency. As expected, all the three finalists took very different approaches to arrive at their recommendations. Team ZIB consisting of Felix Prause and Kai Hoppman, advised by Thorsten Koch, presented an extensive literature review of differen

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MelikeNewcomer
asked in Research & AIMMS Questions
Errors with operators

I tried to multiply a set to a variable in my constraint, which gave the error There is no operation defined for operator "*" with the arguments of data type numeric and data type set. I need to find a solution to avoid this multiplication but come to the same result. sum[j,Stationen*Zuordnung_AufgabenStationen(i,s)]-sum[i,Stationen*Zuordnung_AufgabenStationen(j,s)]<=0

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peddy3009Newcomer
asked in Research & AIMMS Questions
limit a sum

Hello, my model has the following constraint: s(i,j)*x(j)+sum((m,t_), MW(i,j,m,t_)*y(j,m,t_))+sum((k,t_),MWK(i,j,k,t_))+dM(i,j,t)-dP(i,j,t)=B(i,t) The index domain is: (i,j,t) I want the system to accumulate all MWK(i,j,k,t_) respectively all MW(i,j,m,t_)*y(j,m,t_) from t_0 until t_=t and then to add this solution to s(i,j)*x(j). Because t (periods) is already in the index domain I defined a second index t_ in the period set. Unfortunately the system sums up all MWK(i,j,k,t_) over all periods and add this in every t. So if there is a MWK(1,1,1,5)=1 then the system adds this also in t=0. Is there any possibility to determine that the sum should start at t_=0 and end in t_=t? Thanks in advance!

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AIMMS Partner
AnkitBhagatAIMMS Partner
asked in Research & AIMMS Questions
Disable some of Constraints in Model through a user interface

Hi All, I want to create a user interface or page where i can control some of the constraints to toggle and run the model. e.g. Lets say we have 10 set of constraints and I want to run the model with 8 currently while rest 2 I want to disable for the run. This needs to be dynamic Is there any documentation available for the same or any example. Regards Ankit Bhagat

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mohansx
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RachelNewcomer
asked in Research & AIMMS Questions
Implementing a 4-4-5 monthly calendar

I would like to implement a modified monthly calendar, where rather than each month being a strict calendar month, I use the 4 week, 4 week, 5 week pattern. Has anyone used this previously, and if so do have any tips to share? Thanks Rachel

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Katja
asked in Research & AIMMS Questions
Delete a project

Hi, I am using AIMMS for my bachelorthesis. How can I delete a project from "projects"? Thankyou

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Arthur
luiswilbert
luiswilbertEnthusiast
posted in Research & AIMMS Questions
How machine learning and optimization can be applied to Omnichannel Retailing?

Today, the challenge for the companies is providing consistent, yet unique and contextual brand experiences across multiple customer-aware touchpoints, including brick and mortar, marketplaces, web, mobile and social. In response to these new customer preferences, the Omnichannel Strategy has been created to be a fully-integrated approach to coordinate different channels using just one strategy, marketing, price, database, assortment and goals. In this context, optimization models, commonly used for Network Design, Inventory and Fulfillment, may not be the best alternative. I would like to discuss some topics: What are the new business requirement for Omnichannel Retailing? How machine learning, optimization and analytics can be applied to Omnichannel Retailing? What are the biggest challenges for optimization? Thank you in advance

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luiswilbert
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JWandNewcomer
asked in Research & AIMMS Questions
Save Upper and Lower Bounds from Baron

Dear Ladies and Gentleman, I use the solver Baron for a NLP and solve several problems with an if function in the Main Execution. After a specific time limit is exceeded, I want to save the Upper and Lower Bounds in a file or even better in a Parameter. Is this possible? Best regards, Jacqueline Wand

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Jess Es
Patrick
Administrator
PatrickAdministrator
posted in Research & AIMMS Questions
StackExchange got an Operations Research corner

StackExchange got an Operations Research corner now. https://or.stackexchange.com/

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Patrick
Administrator
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Gloria QuintanillaFormer AIMMSian
published in Academic News & Opportunities
Finalist team uses AIMMS for the INFORMS 2019 O.R. & Analytics Student CompetitionBlog

A group of five students from Tilburg University (The Netherlands) made it to the finals of the prestigious INFORMS O.R. & Analytics Student Team competition. The team solved this year’s problem using AIMMS software. In this blog, they will tell us more about the competition and how AIMMS has changed their lives. Who We Are First of all, let’s introduce ourselves. Our team is comprised by two Research Master students in OR (A. Selvi and L.M. Roebers), one Master student in Quantitative Finance and Actuarial Science (N.J. Simons) and two Master students in Business Analytics and OR (T.W.A. Fleuren and W.L.C. Faro). This year, we represented Tilburg University in the INFORMS 2019 O.R. & Analytics Student Team Competition. As one of the six finalist teams out of the total of 292 teams that participated, we were given the opportunity to present our work at the INFORMS 2019 Business Analytics Conference (Austin, Texas). During the project, our team was supervised by Associate Professor Dr.

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sadoflyNewcomer
posted in Research & AIMMS Questions
Bilinear terms in equality constraints (non-convex MIQCP) xy=z?

Hi, I have a non convex MIQCP problem, where the non convexity is illustrated in bilinear constrains like : x+yz=u where x,y,z,u are continuous variables, a general form of this topic is modeling or approaching the constraint : "xy=z" neither gurobi or cplex can handle it. I m wondering, should i use a non linear solver (like Baron)or is there a way to linearize the problem or to approach differently with gurobi or cplex ? Thnaks for your answers.

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Marcel Hunting
AIMMSian
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ChiboEnthusiast
posted in Research & AIMMS Questions
Simple constraint makes the model infeasible

Dear Staff, I am experiencing a weird behaviour within one of my models implemented in AIMMS. I have a simple flow model. Among others, there are the following variables: F, continous variable X, continuous variable The variables do not have lower or upper bounds, so they are free. Then there are some flow balance constraints in the network (i.e. flow in equal to flow out). The model works very fine when only variable F is used. But when I add the following constraint: F = X then I get an infeasible solution. While if I add the constraint F

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ChiboEnthusiast
asked in Research & AIMMS Questions
Modelling question - if then constraint

Dear Staff, I would like your tips for an if-then constraint. In particular, I have the following variables: R, binary variable P, continuous variable Y, continuous variable I have the following parameters: A B The constraints I would like to write are the following: 1) if R=1 then P = A*Y 2) if R=0 then P = B*Y I would like to know if it is possible to have a linear formulation without using indicator constraints. Thank you,

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Jess Es
Jess EsGrand Master
published in Research & AIMMS Questions
Integer and Linear Modeling TricksBlog

Here's a post sourced from the old Tech Blog that points you to some handy tricks for integer and linear modeling! Modeling problems with an (integer) linear program sometimes requires some experience to recognize certain structures in the problem description that can be formulated in a linear way. On the website of the Naval Postgraduate School, you can find the document Formulating Integer Linear Programs: A Rogues’ Gallery that tries to demystify the art of formulating linear and integer linear programs. They do this by introducing formulettes, which consist of a verbal description and the constraints and variables that model this verbal description. The first simple example of a formulette they provide is the following: For each unit of X[sub]1[/sub] , there must be at least 5 units of X[sub]2[/sub] which can be modeled with 5X[sub]1[/sub] <= X[sub]2[/sub] The document contains a lot more such formulettes of varying complexity. Furthermore, in our boo

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Jess Es
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pamjsnnNewcomer
asked in Research & AIMMS Questions
How to code Summation of (inverted A)(w)-element of-W in constraints?

Hi! We were able to execute the model already but we're having warnings that the result for this column is similar with the other column. Take for example the constraints 22 and 26? How do we code the "summation"? Sorry I'm just a beginner and I have no one to teach me and I only have a month to study everything because the deadline is just for 2 months. Our aimms model can be downloaded here: https://drive.google.com/file/d/1zcGWpj_FOGOrUKZiCdutLQ_gxANGrPI6/view?usp=sharingMODEL 2

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deannezhang
AIMMS Champ
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pamjsnnNewcomer
asked in Research & AIMMS Questions
Subtraction of Element Valued Expressions

Hi! I have a constraint (shown at the photo below) wherein two sets need to be subtracted. I tried introducing another set Kw with a definition of k-Ks but it says subtraction of element valued expressions require the set range to be equal, but the ranges domain set "Subblock" and set "Candidate_Subblocks" differ. Identifier: Subblock Index: k Identifier: Candidate_Subblock Index: Ks Identifier: Subblock_Difference Subset of: Subblock, Candidate_Subblocks Index: Kw Definition: k-Ks above is the current code I have. Do you have any Idea on how I can code my constraint?

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deannezhang
AIMMS Champ
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