2,510 research outputs found
Designing a new mathematical model based on ABC analysis for inventory control problem: A real case study
In modern business today, organizations that hold large numbers of inventory items, do not find it economical to make policies for the management of individual inventory items. Managers, thus, need to classify these items according to their importance and fit each item to a certain asset class. The method of grouping and inventory control available in traditional ABC has several disadvantages. These shortcomings have led to the development of an optimization model in the present study to improve the grouping and inventory control decisions in ABC. Moreover, it simultaneously optimizes the existing business relationships among revenue, investment in inventory and customer satisfaction (through service levels) as well as a company's budget for inventory costs. In this paper, a mathematical model is presented to classify inventory items, taking into account significant profit and cost reduction indices. The model has an objective function to maximize the net profit of items in stock. Limitations such as budget even inventory shortages are taken into account too. The mathematical model is solved by the Benders decomposition and the Lagrange relaxation algorithms. Then, the results of the two solutions are compared. The TOPSIS technique and statistical tests are used to evaluate and compare the proposed solutions with one another and to choose the best one. Subsequently, several sensitivity analyses are performed on the model, which helps inventory control managers determine the effect of inventory management costs on optimal decision making and item grouping. Finally, according to the results of evaluating the efficiency of the proposed model and the solution method, a real-world case study is conducted on the ceramic tile industry. Based on the proposed approach, several managerial perspectives are gained on optimal inventory grouping and item control strategies
Complications 15 years after breast augmentation with polyacrylamide
AbstractPolyacrylamide hydrogel (PAAG) has been used as an injectable, permanent filler for soft-tissue augmentation for more than two decades. Several complications have been reported worldwide. In this case report, we present a woman with long-term complications 15 years after bilateral breast augmentation with PAAG injections
Impact of microplastics on organic fouling of hollow fiber membranes
Given the potential hazards of microplastics (MPs), it is desirable to efficiently remove them during wastewater treatment processes. To this end, ultrafiltration (UF) membranes can significantly increase the removal of MPs, however the fouling of such membrane modules can also be impacted by the presence of MPs. Magnetic Resonance Imaging (MRI) was used here to non-invasively quantify the effect of polyethylene (PE) MPs accumulation in a 3D UF hollow fiber (HF) membrane module containing 400 fibers, via direct non-invasive velocity imaging of the flow distribution between individual fibers during module operation. The co-effect of MPs and alginate (a common organic model foulant mimicking extracellular polymeric substances (EPS)) on fouling of the HF module was then explored. Flow was initially equally distributed with fouling causing flow in particular fibers to be significantly reduced. Fouling with MPs resulted in minimal flow distribution disruption and was easily remediated hydraulically, in contrast alginate fouling required chemical cleaning in order to fully restore homogeneous flow distribution between the fibers. The presence of both MPs and alginate resulted in a more heterogeneous disruption of the fibre flow distribution due to fouling and resulted in much more effective hydraulic cleaning of the module
Numerical and analytical investigation on meltpool temperature of laser-based powder bed fusion of IN718
Prediction of meltpool features in Laser-Based Powder Bed Fusion (LB-PBF) is a complex non-linear multiple phase dynamic problem. In this investigation, numerical simulations and analytical models are offered to predict meltpool temperature and to provide a methodology to estimate melt track quality. By determining the meltpool temperature, different rheological phenomena including recoil pressure can be controlled. Recoil pressure is known to drive the keyhole and conduction modes in LB-PBF which is an important factor to qualify the melt track. A numerical simulation was carried out using Discrete Element Method (DEM) with a range of process parameters and absorptivity ratios; allowing observation of the variation of meltpool temperature and free surface morphology, as calculated by the volume-of-fluid (VOF) method. A spatially thermophysical-based analytical model is developed to estimate meltpool temperature, based on LB-PBF process parameters and thermophysical properties of the material. These results are compared with experimentally observed meltpool depth for IN718 specimens and found to have a good accuracy. The numerical and analytic results show good agreement in the conduction mode to estimate the meltpool temperature and related phenomena such as recoil pressure to control the melt track and layering quality. The analytical model does not accurately predict the keyhole mode which may be explained by evaporation of chemical elements in the examined material
Multi-Stage Fuzzy Load Frequency Control Based on Multi-objective Harmony Search Algorithm in Deregulated Environment
A new Multi-Stage Fuzzy (MSF) controller based on Multi-objective Harmony Search Algorithm (MOHSA) is proposed in this paper to solve the Load Frequency Control (LFC) problem of power systems in deregulated environment. LFC problem are caused by load perturbations, which continuously disturb the normal operation of power system. The objectives of LFC are to mini small size the transient deviations in these variables (area frequency and tie-line power interchange) and to ensure their steady state errors to be zero. In the proposed controller, the signal is tuned online using the knowledge base and fuzzy inference. Also, to reduce the design effort and optimize the fuzzy control system, membership functions are designed automatically by the proposed MOHSA method. Obtained results from the proposed controller are compared with the results of several other LFC controllers. These comparisons demonstrate the superiority and robustness of the proposed strategy
Formal Methods for Autonomous Systems
Formal methods refer to rigorous, mathematical approaches to system
development and have played a key role in establishing the correctness of
safety-critical systems. The main building blocks of formal methods are models
and specifications, which are analogous to behaviors and requirements in system
design and give us the means to verify and synthesize system behaviors with
formal guarantees.
This monograph provides a survey of the current state of the art on
applications of formal methods in the autonomous systems domain. We consider
correct-by-construction synthesis under various formulations, including closed
systems, reactive, and probabilistic settings. Beyond synthesizing systems in
known environments, we address the concept of uncertainty and bound the
behavior of systems that employ learning using formal methods. Further, we
examine the synthesis of systems with monitoring, a mitigation technique for
ensuring that once a system deviates from expected behavior, it knows a way of
returning to normalcy. We also show how to overcome some limitations of formal
methods themselves with learning. We conclude with future directions for formal
methods in reinforcement learning, uncertainty, privacy, explainability of
formal methods, and regulation and certification
Long range correlation in cosmic microwave background radiation
We investigate the statistical anisotropy and Gaussianity of temperature
fluctuations of Cosmic Microwave Background radiation (CMB) data from {\it
Wilkinson Microwave Anisotropy Probe} survey, using the multifractal detrended
fluctuation analysis, rescaled range and scaled windowed variance methods. The
multifractal detrended fluctuation analysis shows that CMB fluctuations has a
long range correlation function with a multifractal behavior. By comparing the
shuffled and surrogate series of CMB data, we conclude that the multifractality
nature of temperature fluctuation of CMB is mainly due to the long-range
correlations and the map is consistent with a Gaussian distribution.Comment: 10 pages, 7 figures, V2: Added comments, references and major
correction
Persistent molecular disease in adult patients with AML evaluated with whole-exome and targeted error-corrected DNA sequencing
PURPOSE: Persistent molecular disease (PMD) after induction chemotherapy predicts relapse in AML. In this study, we used whole-exome sequencing (WES) and targeted error-corrected sequencing to assess the frequency and mutational patterns of PMD in 30 patients with AML.
MATERIALS AND METHODS: The study cohort included 30 patients with adult AML younger than 65 years who were uniformly treated with standard induction chemotherapy. Tumor/normal WES was performed for all patients at presentation. PMD analysis was evaluated in bone marrow samples obtained during clinicopathologic remission using repeat WES and analysis of patient-specific mutations and error-corrected sequencing of 40 recurrently mutated AML genes (MyeloSeq).
RESULTS: WES for patient-specific mutations detected PMD in 63% of patients (19/30) using a minimum variant allele fraction (VAF) of 2.5%. In comparison, MyeloSeq identified persistent mutations above 0.1% VAF in 77% of patients (23/30). PMD was usually present at relatively high levels (\u3e2.5% VAFs), such that WES and MyeloSeq agreed for 73% of patients despite differences in detection limits. Mutations in
CONCLUSION: PMD and clonal hematopoiesis are both common in patients with AML in first remission. These findings demonstrate the importance of baseline testing for accurate interpretation of mutation-based tumor monitoring assays for patients with AML and highlight the need for clinical trials to determine whether these complex mutation patterns correlate with clinical outcomes in AML
Comparison of response of canola (Brassica napus L. CV. Hyola 401) to biofertilizer inoculation in optimal and delayed cropping dates
In order to compare the
effects of phosphate solubilizing bacteria as
biofertilizer and mineral phosphorous
application in optimal date of sowing with
delayed cropping date on canola (Brassica
napus L.) growth and productivity, a splitplot
experiment, using randomized complete
block design with three replications, was
conducted at Dashate-Naz Agronomy
Research Station, in 2014. Four levels of
bacterial inoculation (Pseudomonas putida,
Pseudomonas fluorescens, singly or in
combination) were applied as main plots
and five levels of mineral phosphorus (P)
application (0, 25, 50, 75, and 100 kg·ha-1 of
mineral phosphorous) were applied as sub
plots. Canola plant were sown at two dates
of sowing, one at optimal date of sowing
(30 Sept., 2014) and the other one month
later as delayed cropping (30 Oct., 2014).
The results obtained showed that effects of
bacterial inoculation on number of seeds per
pod, number of pods on plant, and seed
yield were significant at one percent
probability level at both sowing dates.
Moreover, rates of phosphate application
had significant effects on all traits at one
percent level. Comparing the means showed
that application of mineral P resulted in
substantial increase in seed yield. At
optimal date of sowing, it was shown that
while minimum seed yield obtained at
control treatment (1600 kg·ha-1), the
maximum (2980 kg·ha-1) obtained with
interaction effects of application of both
bacterial strains along with 75 kg·ha-1 mineral P, having no statistically difference
with that of P. fluorescens, along with 75
kg·ha-1 mineral P (2940 kg·ha-1). It was
shown that delayed cropping resulted in
decreasing canola growth which is reflected
in seed yield and yield components.
Minimum seed yield at control plot at first
date of sowing (1600 kg·ha-1) decreased to
740 kg·ha-1, in the second date of sowing,
showing 54 % decrease. The maximum seed
yield also decreased in delayed cropping,
from 2980 kg·ha-1 at 30 Sept., 2014, as
compared to 1074 kg·ha-1 at 30 Oct., 2014,
showing a 64% decrease. The results
obtained showed that an increase in P level,
eventually enhanced the seed yield. This
increasing trend continued until a threshold
level (75 kg·ha-1 of P), after which seed
yield showed a declining fashion
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