critical chain
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2022 ◽  
pp. 526-544
Author(s):  
Brian J. Galli

This purpose of this article is to assess constraints and suggest a theory that can improve Human Resource Management Systems (HRMS's). It investigates the relationship between Theory of Constraints (TOC) and operation management, which is based on the Critical Chain PMs book entitled The Goal. In 1984, the author, Goldratt, introduced an entire management philosophy about the TOC. The mental process and improvement theory tools discussed in his book mainly focus on manufacturing environments. However, the practice and examples in the book helped many organizations succeed, even in the private sectors. This study offers definitions of throughput, operating expense, and inventory measurements, and uses the principle of TOC to identify bottlenecks and constraints in every business process. By using these analyses, the study remodels the system to increase performance measurements of HRMS.


Author(s):  
Mojtaba Delfanian ◽  
M. A. Sahari ◽  
Mohsen Barzegar ◽  
Hassan Ahmadi Gavlighi ◽  
Francisco Jose Barba

From an interfacial phenomena standpoint, the effect of length of alkyl chain was evaluated on activities of gallic acid and its alkyl ester derivatives in supramolecular oxidation of stripped soybean oil. The gallic acid molecules (log P = -0.47) with an electron-donating carboxylate anion had a higher scavenging activity against DPPH• than alkyl gallates. Interfacial activities of gallates in emulsion and bulk oil improved as the lengths of the alkyl chain were reached until a critical chain length; after that, further chain length extension causes a decrease in potency. In β-carotene bleaching and Rancimat assays higher inhibitory effect was observed for dodecyl and propyl gallate, respectively. Evaluation of interfacial tension, water content, and droplet size of hydroperoxides reverse micelles in parallel with lipid peroxidation indicated that the inhibitory effect of the alkyl gallates, especially methyl gallate, was significantly better than the gallic acid in the bulk phase oil.


2021 ◽  
Vol 16 (03) ◽  
pp. 01-20
Author(s):  
Taynara Takami Narita ◽  
Caio Henrique Alberconi ◽  
Fernando De Souza ◽  
Lucas Ikeziri

Purpose: Evaluate and compare PERT/CPM and Critical Chain Project Management (CCPM) techniques, from the Theory of Constraints (TOC), in relation to indicators of delivery time estimation and reliability in meeting established deadlines. Theoretical framework: The research is based on the time management theory established by the PERT/CPM and CCPM methods. Design/methodology/approach: This work has an experimental character, using a method of computer simulation by applying the Promodel software. A fictitious project environment managed by PERT/CPM and CCPM techniques was modeled in order to evaluate and compare their performances in terms of estimation of, and compliance with, project completion deadlines. Findings: The results obtained showed that the CCPM method proved to be more effective in reducing project completion time and meeting established deadlines. Conversely, the PERT/CPM method increased planned project completion time by 189%. Research, Practical & Social implications: Many managers assume that the best approach to project planning, especially when aiming for short and reliable deadlines, is to allocate margins of safety to each scheduled activity. This research reinforced the already widely held perception of TOC that, due to certain ordinary human behaviors, local optimizations do not guarantee, and usually adversely effect, good global results. Originality/value: There is a lack of research comparing PERT/CPM and CCPM techniques through modeling and computer simulations of project environments subjected to certain degrees of uncertainty, particularly in terms of performance variables such as those studied here. The results of this research, therefore, address this opportunity, bringing to light comparative scenarios and explanations for the different behaviors observed. Keywords: Computational Simulation; Project Management; Goldratt; Critical Chain; CCPM; PERT/CPM.


Symmetry ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1751
Author(s):  
Alireza Mashaghi ◽  
Roland van der Veen

The topological framework of circuit topology has recently been introduced to complement knot theory and to help in understanding the physics of molecular folding. Naturally evolved linear molecular chains, such as proteins and nucleic acids, often fold into 3D conformations with critical chain entanglements and local or global structural symmetries stabilised by formation contacts between different parts of the chain. Circuit topology captures the arrangements of intra-chain contacts within a given folded linear chain and allows for the classification and comparison of chains. Contacts keep chain segments in physical proximity and can be either mechanically hard attachments or soft entanglements that constrain a physical chain. Contrary to knot theory, which offers many established knot invariants, circuit invariants are just being developed. Here, we present polynomial invariants that are both efficient and sufficiently powerful to deal with any combination of soft and hard contacts. A computer implementation and table of chains with up to three contacts is also provided.


Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5795
Author(s):  
Janusz Kulejewski ◽  
Nabi Ibadov ◽  
Jerzy Rosłon ◽  
Jacek Zawistowski

This study concerns the use of the critical chain method to schedule the construction of renewable energy facilities. The critical chain method is recognized as a useful project management tool, transforming a stochastic problem of uncertainty in activity durations into a deterministic one. However, this method has some shortcomings. There are no clear principles of grouping non-critical activities into feeding chains. Another ambiguity is sizing the feeding buffers with regard to the topology of the network model and the resulting dependencies between activities, located in different chains. As a result, it is often necessary to arbitrarily adjust the calculated sizes of feeding buffers before inserting them into the schedule. The authors present the new approach to sizing the time buffers in the schedule, enabling a quick assessment of the quality of a given solution variant and finding a solution that best meets the established criteria, conditions, and constraints. The essence of the presented approach is the two-step sizing of time buffers with the use of deterministic optimization and stochastic optimization techniques. Taking into account construction management needs, the optimization criteria are based on the construction project cash flow analysis. The effectiveness of the presented approach is illustrated by an example of developing a wind power plant construction schedule. According to the results, the presented approach ensures the protection of the scheduled completion date of the construction and the stability of the schedule.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Tarek Salama ◽  
Ahmad Salah ◽  
Osama Moselhi

Purpose The purpose of this paper is to present a new method for project tracking and control of integrated offsite and onsite activities in modular construction considering practical characteristics associated with this type of construction. Design/methodology/approach The design embraces building information modelling and integrates last planner system (LPS), linear scheduling method (LSM) and critical chain project management (CCPM) to develop tracking and control procedures for modular construction projects. The developed method accounts for constraints of resources continuity and uncertainties associated with activity duration. Features of proposed method are illustrated in a case example for tracking and control of modular projects. Findings Comparison between developed schedule and Monte Carlo simulation showed that baseline duration generated from simulation exceeds that produced by developed method by 12% and 10% for schedules with 50% and 90% confidence level, respectively. These percentages decrease based on interventions of members of project team in the LPS sessions. The case example results indicate that project is delayed 5% and experienced cost overrun of 2.5%. Originality/value Developed method integrated LPS, LSM and CCPM while using metrics for reliability assessment of linear schedules, namely, critical percent plan complete (PPCcr) and buffer index (BI). PPCcr and BI measure percentage of plan completion for critical activities and buffer consumption, respectively. The developed method provides a systematic procedure for forecasting look-ahead schedules using forecasting correction factor Δt and a newly developed tracking and control procedure that uses PPCcr and BI. Quantitative cost analysis is also provided to forecast and monitor project costs to prove the robustness of proposed framework.


2021 ◽  
Author(s):  
Xiaokang Han ◽  
Wenzhou Yan ◽  
Ting Liu

Abstract It has been widely accepted in the academic community that the Critical Chain Method (CCM) has significant advantages over the Critical Path Method (CPM) in solving the problem with resource constraints. However, this paper conducted a study on comparing the two methods of Critical Chain Method and Critical Path Method, and found that the only difference between those two methods lies in how to determine the priority of resources allocating, and on the assumption of not setting buffer zone, those two methods have no essential distinctions at all. By establishing the relationship between CCM and CPM, this paper also enriched and improved CCM to some extent, and pointed out that the buffer zone setting in CCM is merely subjective and short of scientificity. In the meantime, for the problem of unclear representation of critical chains, it proposed two ways of representing critical chains and related rules to follow. To verify the conclusion of this paper, further detailed case study of comparing CCM and CPM was performed. Affected by various uncertain factors, the project construction sequence is random, the total construction duration is random, and the critical chain is also random, so it is unable to determine how to direct construction. Aiming at the randomness of the critical chain, this article analyzed various uncertain factors of the critical chain, and on the basis of solving the critical chain sequence time, it proposed the approach to determine the completion probability of the total construction duration and control the construction of the critical chain to direct the construction, in the meantime, the inverse algorithm was adopted to determine of the construction duration under the condition of required completion probability.


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