A bi-objective genetic algorithm approach to risk mitigation in project scheduling

A problem of risk mitigation in project scheduling is formulated as a bi-objective optimization problem, where the expected makespan and the expected total cost are both to be minimized. The expected total cost is the sum of four cost components: overhead cost, activity execution cost, cost of reducing risks and penalty cost for tardiness. Risks for activities are predefined. For each risk at an activity, various levels are defined, which correspond to the results of different preventive measures. Only those risks with a probable impact on the duration of the related activity are considered here. Impacts of risks are not only accounted for through the expected makespan but are also translated into cost and thus have an impact on the expected total cost. An MIP model and a heuristic solution approach based on genetic algorithms (GAs) is proposed. The experiments conducted indicate that GAs provide a fast and effective solution approach to the problem. For smaller problems, the results obtained by the GA are very good. For larger problems, there is room for improvement

A biobjective genetic algorithm approach to project scheduling under risk

A problem of risk mitigation in project scheduling is formulated as a bi-objective optimization problem, where the expected makespan and the expected total cost are both to be minimized. The expected total cost is the sum of four cost components: overhead cost, activity execution cost, cost of reducing risks and penalty cost for tardiness. Risks for activities are predefined. For each risk at an activity, various levels are defined, which correspond to the results of different preventive measures. Only those risks with a probable impact on the duration of the related activity are considered here. Impacts of risks are not only accounted for through the expected makespan but are also translated into cost and thus have an impact on the expected total cost. An MIP model and a heuristic solution approach based on genetic algorithms (GAs) is proposed and tested. The experiments conducted indicate that GAs provide a fast and effective solution approach to the proble m. For smaller problems, the results obtained by the GA are very good. For larger problems, there is room for improvement

Multiobjective genetic algorithm approaches to project scheduling under risk

In this thesis, project scheduling under risk is chosen as the topic of research. Project scheduling under risk is defined as a biobjective decision problem and is formulated as a 0-1 integer mathematical programming model. In this biobjective formulation, one of the objectives is taken as the expected makespan minimization and the other is taken as the expected cost minimization. As the solution approach to this biobjective formulation genetic algorithm (GA) is chosen. After carefully investigating the multiobjective GA literature, two strategies based on the vector evaluated GA are developed and a new GA is proposed. For these three GAs first the parameters are investigated through statistical experimentation and then the values are decided upon. The chosen parameters are used for the computational study part of this thesis. In this thesis three improvement heuristics are developed also to further improve the GA solutions. The aim of these improvement heuristics is to decrease the expected cost of the project while keeping the expected duration of the project fixed. These improvement heuristics are implemented at the end of the proposed GA and used to improve the results of the proposed GA. Finally the GAs and improvement heuristics are tested on three different sets of problems. The results are evaluated by pairwise comparisons of algorithms and of heuristics. Also an approximation of the true Pareto front is generated using the commercial mathematical modelling program, GAMS. The results are compared to that approximation and they seem comparable to that solution. The results of the improvement heuristics are also compared against each other and the performance of the heuristics is reported in detail

The relationship between professional burnout and job satisfaction levels of employee: A study into employees in hotel enterprises

The main aim of this paper is to determine the levels of professional burnout and job satisfaction of employees in five-star hotels and to expose the relationship between them.  Especially professional burnout has been popular field of research to appear with increasing frequency in job satisfaction. Professional burnout has been investigated in three basic dimensions: Emotional exhaustion, depersonalization and personal accomplishment. Boring and highly stressed work environment, long and intensive work hours, problems and policies of low-wage employment in hotel enterprises, attitudes and behaviors of executives and managers towards employees have increased the appearing probability of job burnout in tourism industry. Job satisfaction is one’s own positive, negative and neutral all emotions; feelings and thoughts towards the business and the results emerged from these emotions on people. Population of this study is made of employees working at five-star hotels in Istanbul. In this frame, clustering sampling method was used and eight hotel enterprises were treated as a cluster. In the study, the differences of hotel workers’ opinions toward the job satisfaction and job burnout by demographic characteristics were analyzed using t-test and analysis of variance (ANOVA). In addition, Correlation and Regression Analysis were conducted to determine the relationship between professional burnout and job satisfaction levels. According to the results of correlation and regression analyses, it is found out  that professional burnout level has a significant effect on job satisfaction level of the employees

The relationship between professional burnout and job satisfaction levels of employee: A study into employees in hotel enterprises

The main aim of this paper is to determine the levels of professional burnout and job satisfaction of employees in five-star hotels and to expose the relationship between them. Especially professional burnout has been popular field of research to appear with increasing frequency in job satisfaction. Professional burnout has been investigated in three basic dimensions: Emotional exhaustion, depersonalization and personal accomplishment. Boring and highly stressed work environment, long and intensive work hours, problems and policies of low-wage employment in hotel enterprises, attitudes and behaviors of executives and managers towards employees have increased the appearing probability of job burnout in tourism industry. Job satisfaction is one’s own positive, negative and neutral all emotions; feelings and thoughts towards the business and the results emerged from these emotions on people. Population of this study is made of employees working at five-star hotels in Istanbul. In this frame, clustering sampling method was used and eight hotel enterprises were treated as a cluster. In the study, the differences of hotel workers’ opinions toward the job satisfaction and job burnout by demographic characteristics were analyzed using t-test and analysis of variance (ANOVA). In addition, Correlation and Regression Analysis were conducted to determine the relationship between professional burnout and job satisfaction levels. According to the results of correlation and regression analyses, it is found out that professional burnout level has a significant effect on job satisfaction level of the employees

Green tea extract exerts anabolic effects on extracellular matrix of the skin

An in vitro trial was carried out to reveal the effects of an extract of Camellia sinensis (green tea extract) on the major extracellular matrix components of human skin. After preparing the green tea extract its phytochemical contents were analysed and its effects on gene expression of hyaluronan synthase 2, matrix metalloproteinase-9 and elastase in a human dermal fibroblast cell line were determined. Cell proliferation assay was performed using XTT reagent. Ribonucleic acid isolations were realized by using TRI reagent. Expressions of the relevant enzymes and a control enzyme glyceraldehyde-3-phosphate dehydrogenase were determined using RT-qPCR analysis. Green tea extract caused statistically significant upregulation of hyaluronan synthase-2 gene expression compared to untreated control cells. Also, as a positive outcome, the treatment resulted in significant downregulations of matrix metalloproteinase-9 and elastase gene expressions. Green tea extract was found to have substantial anabolic effects on hyaluronic acid, collagen and elastin. The results obtained in this study might partially explain the molecular basis of the health benefits and antiaging effects of Camellia sinensis on skin

Učinak različitih metoda standardizacije suhe tvari na mineralni sastav jogurta

Yoghurt is a good dietary source of macro and micro minerals. However, the mineral content of yoghurt can vary according to the technological processing used in its manufacture. In this context, the aim of this study was to compare some macro (Ca, K and Mg) and micro (As, Cd, Co, Fe, Mn, Ni, Pb, Se, V and Zn) mineral contents of total solids-standardized yoghurts with four different methods by following: (1) Addition of skim milk powder to milk, (2) Concentration of yoghurt milk by vacuum evaporation, (3) Concentration of yoghurt curd in a cloth bag and (4) Concentration of yoghurt curd by mechanical centrifugation. The highest content of the macro minerals was in the yoghurt produced with method 1, while the highest content of most of the micro minerals was in the yoghurt produced with method 4. The results of this study showed that the mineral content of yoghurt could be modified by the method used in the manufacture of yoghurt to standardize total solids content.Jogurt je dobar prehrambeni izvor makro i mikro elemenata. Međutim, udio mineralnih tvari u jogurtu može varirati ovisno o tehnološkoj obradi koja se koristi pri njegovoj proizvodnji. U skladu s tim, cilj ove studije bio je usporediti sadržaj nekih makro (Ca, K i Mg) i mikro (As, Cd, Co, Fe, Mn, Ni, Pb, Se, V i Zn) elemenata u suhoj tvari jogurta standardiziranom primjenom sljedeće četiri metode: (1) dodavanjem obranog mlijeka u prahu; (2) koncentriranjem mlijeka uparivanjem u vakuumu; (3) koncentriranjem koaguluma jogurta u sirarskoj vreći; i (4) koncentriranjem koaguluma jogurta mehaničkim centrifugiranjem. Najveći sadržaj makro elemenata utvrđen je u jogurtu proizvedenom metodom 1, dok je najveći sadržaj većine mikro elemenata utvrđen u jogurtu proizvedenom metodom 4. Rezultati ove studije pokazali su da se sadržaj mineralnih tvari u jogurtu može podešavati primjenom različitih metoda standardizacije suhe tvari

Analysis of the kefir and koumiss microbiota with the focus on certain functional properties of selected lactic acid bacteria

Cilj ovog rada bio je odrediti mikrobiotu komercijalno dostupnog kefira, kumisa i kefira proizvedenog u kućnoj radinosti primjenom metagenomičke analize te usporediti neka probiotička svojstva bakterija mliječne kiseline izoliranih iz tih napitaka sa sojem Lactobacillus casei koji se koristi u proizvodnji yakulta. Kao uzorci korišteni su jedan kefir iz kućne radinosti, pet komer¬cijalno dostupnih kefira različitih proizvođača i jedan kumis. Mikrobna raznolikost kefira i kumisa određena je metagenomičkom analizom na ciljano područje V1-V2 16S rRNK gena. Direktnom izolacijom DNK utvrđeno je da su u komercijalno dostupnim uzorcima kefira dominantne vrste Streptococcus thermophilus i Lactococcus lactis. Izolacijom na MRS agaru dominantnim su se pokazali Lc. lactis i Leuconostoc mesenteroides, dok je izolacijom na M-17 agaru dominantna vrsta bila Lc. lactis. U kefiru iz kućne radinosti koji je proizveden pomoću kefirnih zrnaca, dominantna vrsta bio je Lb. kefiranofaciens. Lb. kefiri i Enterococcus durans pokazali su se dominantnim vrstama izolacijom na MRS I M-17 agaru. Lb. kefiranofaciens, Lb. kefiri, i Str. thermophilus su bile dominantne vrste u kumisu. Mikroorganizmi izolirani iz kumisa pokazali su osnovna probiotička svojstva slično bakteri¬jama mliječne kiseline izoliranim iz yakulta. Ovo istraživanje daje prikaz bakterijske mikroflore i probiotičkih svojstava bakterija mliječne kiseline izoliranih iz kefira i kumisa koji se konzumiraju u Turskoj.The aim of this research was to determine the microbiota of commercial kefir, koumiss and homemade kefir samples using metagenomic analysis and compare some probiotic properties of lactic acid bacteria isolated from these beverages and Lactobacillus casei, used in yakult production. One koumiss, 5 commercially available kefir beverages with different brands, and 1 homemade kefir were used as samples. Microbial diversity of kefir and koumiss samples were determined by metagenomic analysis, targeting V1-V2 region of 16S rRNA gene. Streptococcus thermophilus and Lactococcus lactis were detected as dominant in direct DNA isolation from commercially available kefir beverages. Lc. lactis and Leuconostoc mesenteroides were dominant in MRS agars, and Lc. lactis were dominant in M17 agars. In kefir beverages produced by kefir grains, Lb. kefiranofaciens was determined as the dominant bacteria. Lb. kefiri and Enterococcus durans were found dominant in MRS and M17 agars respectively. Lb. kefiranofaciens, Lb. kefiri, and Str. thermophilus were the dominant bacterias of koumiss beverages. Microorganisms isolated from kefir and koumiss beverages were found to exhibit basic probiotic properties, similar to the lactic acid bacteria isolated from yakult. This research presented bacterial microflora and probiotic properties of lactic acid bacteria isolated from kefir and koumiss beverages consumed in Turkey