Investigation of the production cycle management process of a complex product

У раду је приказано истраживање процеса управљања производним циклусом сложеног производа и дати су одговори на питања и дилеме који су актуелни у научној и стручној јавности дужи низ година. Анализом научних и стручних достигнућа уочене су недоумице, нејасноће и отворена питања везана за теорију производних циклуса. На основу тога дефинисана је истраживачка платформа, полазне хипотезе, план истраживања и структура дисертације. Са једне стране, наметнуло се питање валидности постојећих решења, релација и модела, а са друге стране, истраживање нових и њихова провера у пракси. У фокусу истраживања налази се сложен производ који представља генератор свих збивања унутар и изван пословно-производних система. Развијени су теоријски модели за опис структуре сложеног производа који представљају основу за дефинисање осталих модела: за прорачун количина производних фаза; оптимизацију производне серије; прорачун технолошких и пројектовање производних циклуса на нивоу технолошке операције, производне фазе и сложеног производа; ангажовање обртних средстава и процену квалитета пројектованих решења помоћу одговарајућих показатеља проточности. Експериментални део истраживања спроведен је у Компанији "Слобода" Чачак где су верификовани сви развијени модели и софтверска решења у условима серијске понављајуће производње са прекидним током технолошког процеса. Производњу карактерише глобализација пословања, велики број сложених производа, разноврсне технологије и опрема, вишеваријантна технолошка решења и уградња истих делова у више различитих производа. Корист од истраживања је вишеструка, како у теоријском тако и у практичном смислу, јер је омогућена примена теоријских модела у разноврсним условима производње и пословања. Актуелност, ширина и значај теме као и постигнути резултати дају добру основу за даља истраживања у овој области.The work presents the investigation of the production cycle management process of a complex product, providing answers to the questions and dilemmas that have been current in professional community for a number of years. The analysis of scientific and professional achievements pointed to the doubts, uncertainties and open issues related to the theory of production cycles. Using those findings, the investigation platform, starting hypotheses, plan of investigation and doctoral dissertation structure were all defined. On one hand, the question of the validity of existing solutions, relations and models was raised and, on the other hand, the investigation of new ones and their testing in practice. The focus of investigation is a complex product representing the generator of all activities inside and outside of the business-production systems. Theoretical models were developed for describing the complex product structure, generating the basis for defining the other models: for calculating the amount of production cycles, production batch optimization, calculating technological and production cycle design at the level of technological operations, production cycle and complex product; engagement of working capitals and evaluation of designed solutions using the corresponding flow indicators. The experimental part of the investigation was conducted at “Sloboda” Company Čačak, where all developed models and software solutions were verified under conditions of series, repeating production with an interrupting technological process flow. Production is characterized by the globalization of operating business, a large number of complex products, a variety of technologies and equipment, multi-variety technological solutions and installment of the same parts into a number of different products. The benefit of this investigation is multiple, in both theoretical and practical respect, because the application of theoretical models is enabled in various production and business operating conditions. Actuality, breadth and significance of the theme as well as the achieved results provide a solid basis for further investigations in this area

Manufacturing Cycle Time Analysis and Scheduling to Optimize Its Duration

This paper reports the results of investigations on manufacturing cycle times for special-purpose products. The company performs serial production characterized by complex and diverse technologies, alternative solutions and combined modes of workpiece movement in the manufacturing process. Because of various approaches to this problem, an analysis of previous investigations has been carried out, and a theoretical base is provided for the technological cycle and factors affecting the manufacturing cycle time. The technological and production documentation of the company has been analysed to establish the technological and real manufacturing cycle times, total losses and flow coefficients. This paper describes the original approach to production cycle scheduling on the grounds of investigations of manufacturing capacity utilization levels and causes of loss, in order to measure their effects and to reduce the flow coefficient to an optimum level. The results are a segment of complex studies on the production cycle management of complex products, accomplished in the company in the period from 2010 to 2012

Manufacturing Cycle Time Analysis and Scheduling to Optimize Its Duration

This paper reports the results of investigations on manufacturing cycle times for special-purpose products. The company performs serial production characterized by complex and diverse technologies, alternative solutions and combined modes of workpiece movement in the manufacturing process. Because of various approaches to this problem, an analysis of previous investigations has been carried out, and a theoretical base is provided for the technological cycle and factors affecting the manufacturing cycle time. The technological and production documentation of the company has been analysed to establish the technological and real manufacturing cycle times, total losses and flow coefficients. This paper describes the original approach to production cycle scheduling on the grounds of investigations of manufacturing capacity utilization levels and causes of loss, in order to measure their effects and to reduce the flow coefficient to an optimum level. The results are a segment of complex studies on the production cycle management of complex products, accomplished in the company in the period from 2010 to 2012

Antioxidative enzymes in the response of buckwheat (Fagopyrum esculentum Moench) to complete submergence

Oxidative stress and antioxidative defense system activity were studied in buckwheat leaves after complete submergence and re-aeration. The levels of H2O2 and lipid peroxidation were found to be significantly higher in stressed than in untreated buckwheat leaves. Enzymes catalyzing the degradation of H2O2 and peroxides were shown to participate actively, whereas superoxide dismutase did not take part in the buckwheat leaf response to flooding stress. The most prominent increase in antioxidative enzyme activities was noticed upon return to air, when the strongest oxidative stress occurred and the need for antioxidative defense was the greatest

Uticaj postupka sinteze na aktivnost platinskih katalizatora za reakciju elektrooksidacije etanola

Carbon supported platinum catalysts for ethanol electrooxidation were synthesized by modified polyol synthesis method, assisted by microwave or reflux heating. Synthesized catalysts were characterized by XRD, STM and TGA techniques to determine their structural and morphological properties. STM and XRD investigations revealed small particle size (~3nm), while TGA showed Pt loading of 20% in both samples. Electrocatalytic activity of prepared catalysts was examined by potentiodynamic measurements and compared to commercial Pt catalyst (Pt/C-Tanaka). The highest activity for ethanol electrooxidation was observed with Pt catalyst prepared by microwave irradiation. The increase in activity can be assigned to the benefits of microwave assisted synthesis, such as small particle size and homogeneous particle distribution on the support.Platinski katalizatori na ugljeničnoj podlozi su sintetizovani korišćenjem modifikovanog poliol postupka uz primenu mikrotalasnog ili refluks zagrevanja za reakciju elektrooksidacije etanola. Dobijeni katalizatori su karakterisani strukturno i morfološki korišćenjem XRD, STM i TGA tehnika. STM i XRD ispitivanja su pokazala malu veličinu čestica (~3nm), dok je TGA pokazala da je sadržaj metala u katalizatoru 20%. Elektrokatalitička aktivnost sintetizovanih katalizatora je ispitivana potenciodinamičkim merenjima i upoređena sa komercijalnim platinskim katalizatorom (Pt/C-Tanaka). Najbolju aktivnost za elektrooksidaciju etanola pokazao je platinski katalizator sintetizovan uz korišćenje mikrotalasnog zagrevanja. Veća aktivnost se može pripisati prednostima mikrotalasnog zagrevanja u toku sinteze jer je dobijen katalizator sa malom veličinom i homogenom di stribucijom čestica

Structural, Electronic and Mechanical Properties of Superhard B4C from First Principles

Boron carbide (B4C) has attracted great attention as a semiconducting material with excellent properties and has found various technological applications. High hardness value makes it a potentially superhard material as well as a low density, high degree of chemical inertness, high melting temperature, thermal stability, abrasion resistance, and excellent neutron absorption, contributed to the use of boron carbide as an abrasive material for extreme conditions, wear resistance components, body armors and as a nuclear absorber or solid-state neutron detector. However, B4C is known for its unusual structure, bonding, and substitutional disordering whose nature is not yet fully understood, and exhibits brittle impact behavior. In this study we investigated the chain-model structure with an arrangement of 12-boron atom icosahedra and linear 3-carbon atom chains, using available experimental data. We employed the DFT method with LDA and GGA- PBE functional, as implemented in the CRYSTAL17 software package. Electronic properties of boron carbide have been investigated by calculating the density of states (DOS) and band structure. Calculated mechanical properties have been investigated: bulk modulus, shear modulus, Young modulus, Poisson’s ratio, hardness, and elastic tensor constants, and compared with available experimental data

Mikrotalasna sinteza i karakterizacija Pt i Pt-Rh-Sn katalizatora za oksidaciju etanola

Carbon-supported Pt and Pt-Rh-Sn catalysts were synthesized by the microwave-polyol method in ethylene glycol solution and were investigated in the ethanol electro-oxidation reaction. The catalysts were characterized in terms of structure, morphology and composition employing the X-ray diffraction (XRD), scanning tunneling microscopy and energy-dispersive X-ray spectroscopy techniques. The STM analysis indicated rather uniform particles and particle sizes below 2 nm for both catalysts. The XRD analysis of the Pt/C catalyst revealed two phases, one with the main characteristic peaks of the face-centered cubic crystal structure (fcc) of platinum and the other related to the graphite-like structure of the carbon support, Vulcan XC-72R. However, in the XRD pattern of the Pt-Rh-Sn/C catalyst, diffraction peaks for Pt, Rh or Sn could not be resolved, indicating extremely low crystallinity. The small particle sizes and homogeneous size distributions of both catalysts could be attributed to the advantages of the microwave-assisted modified polyol process in ethylene glycol solution. The Pt-Rh-Sn/C catalyst was highly active for ethanol oxidation with the onset potential shifted by more than 150 mV to more negative values and with currents nearly 5 times higher in comparison to the Pt/C catalyst. The stability tests of the catalysts, as studied by chronoamperometric experiments, revealed that the Pt-Rh-Sn/C catalyst was evidently less poisoned than the Pt/C catalyst. The increased activity of Pt-Rh-Sn/C in comparison to Pt/C catalyst was most probably promoted by the bi-functional mechanism and the electronic effect of the alloyed metals.Pt i Pt-Rh-Sn katalizatori na ugljeniku razvijene površine su sintetizovani poliol-mikrotalasnim postupkom u rastvoru etilenglikola i ispitivani za reakciju eletrohemijske oksidacije etanola u kiseloj sredini. Katalizatori su okarakterisani strukturno, morfološki i po sastavu korišćenjem XRD, STM i EDX tehnika. STM analiza je potvrdila da su Pt i Pt-Rh-Sn čestice uniformne veličine i prečnika manjeg od 2 nm. XRD analiza Pt/C katalizatora pokazala je prisustvo dve faze, jedne sa glavnim karakterističnim pikovima za pljosno-centriranu kubnu kristalnu strukturu platine (111, 200, 220 i 311) i druge sa difrakcionim pikom na 2q oko 25° karakterističnim za heksagonalnu strukturu vulkana XC-72R (ugljeničnog nosača). XRD analiza Pt-Rh-Sn/C katalizatora nije pokazala karakteristične pikove, što je indikacija veoma male kristaličnosti katalizatora. Aktivnost katalizatora ispitivana je potenciodinamičkim i hronoamperometrijskim merenjima. Pt-Rh-Sn/C katalizator je veoma aktivan za oksidaciju etanola sa početkom reakcije na potencijalima za oko 150 mV pomerenim ka negativnijim vrednostima i strujama koje su oko pet puta veće u poređenju sa Pt/C katalizatorom. Stabilnost katalizatora ispitivana hronoamperometrijski pokazala je da se Pt-Rh-Sn/C katalizator manje truje od Pt/C katalizatora. Mala veličina i homogena distribucija čestica mogu se pripisati prednostima mikrotalasne sinteze i modifikovanog poliol postupka u rastvoru etilenglikola. Veća aktivnost Pt-Rh-Sn/C katalizatora u poređenju sa Pt/C katalizatorom posledica je bi-funkcionalnog mehanizma i elektronskog (ligand) efekta metala u sintetizovanoj leguri

Vitamin D Status and Its Correlation With Anthropometric and Biochemical Indicators of Cardiometabolic Risk in Serbian Underground Coal Miners in 2016

The status of vitamin D in underground working coal miners and its association with their cardiometabolic health is rarely studied. This study aimed to examine vitamin D (VitD) status in Serbian underground coal miners and to correlate it with anthropometric and laboratory indicators of cardiometabolic risk. Nutritional data (food frequency questionnaire, FFQ, and two times repeated 24 h recall), anthropometric data (including segmental analysis by bio-impedance analyzer TANITA BC-545N), arterial tension, and biochemical and hematological data of 103 coal miners (aged 22–63 years) were correlated with their late summer (early September) serum 25 (OH)D levels (measured by HPLC). 68.9% of the studied coal miners were overweight/obese, and 48.5% had metabolic syndrome. Their mean VitD nutritional intakes were low: 5.3 ± 3.8 μg/day (FFQ) and 4.9 ± 8 μg/day (24 h recalls), but their mean serum 25 (OH)D levels were surprisingly high (143.7 ± 41.4 nmol/L). Only 2.9% of the coal miners had 25(OH)D levels lower than 75 nmol/L (indicating an insufficient/deficient status), while 63.2% had values above 125 nmol/L (upper optimal limit), and even 10.7% had values above 200 nmol/L. There were no statistical differences in 25 (OH)D levels in the coal miners with or without metabolic syndrome (or overweight/obesity). Interestingly, 25(OH)D levels had significant positive correlations with body mass index (BMI), fat mass (FM), fat mass percentage (FM%), limbs FM%, serum triglycerides, GGT, AST, ALT, and ALT/AST ratio, and had significant negative correlations with serum HDL-cholesterol and age. All these correlations were lost after corrections for age, FM, FM%, and legs FM%. In Serbian coal miners, high levels of early September VitD levels were observed, indicating sufficient non-working-hour sun exposure during the summer period. Furthermore, the unexpected positive correlations of VitD levels with anthropometric and biochemical parameters indicative of obesity, metabolic syndrome, and fatty liver disease were found. More research is needed on the VitD status of coal miners (particularly in the winter period) and its relationship with their cardiometabolic status

A novel spi1 mutation in a patient with agammaglobulinemia

Agammaglobulinemia is a primary immunodeficiency characterized by a low number or absence of mature B lymphocytes and consequently by immunoglobulin deficiency. In 2021, six patients with pathogenic variants in SPI1 gene associated with agammaglobulinemia type 10 (PU.MA) were described for the first time. This gene encodes the pioneer transcription factor PU.1, which plays an important role in the differentiation of B lymphocytes, monocytes, and conventional dendritic cells. Here we present a female patient with a novel mutation in SPI1 gene which has not been previously found in patients with PU.MA. Case description: A 37-year-old female patient with frequent middle ear infections in early childhood was diagnosed with agammaglobulinemia at the age of 15 when she started immunoglobulin replacement therapy (IgRT). One year later, an allogeneic hematopoietic stem cell transplant from a healthy sibling donor was performed. Unfortunately, chimerism analysis found no DNA material from the donor in the patient's blood, suggesting graft rejection, so she remained dependent on antibody replacement therapy. Years later, she was diagnosed with protein-losing enteropathy, and despite escalating doses of IgRT, IgG levels remained low. Subsequently, the patient developed persistent COVID -19 viremia and bacterial meningoencephalitis. Clinical exome sequencing using the TruSight (Illumina) panel was performed and in comparision with the human reference genome (hg19), has revealed a heterozygous mutation in exon 4 of the SPI1 gene. This mutation is characterized by the insertion of 2 nucleotides (c.441dup), a reading frame shift, and the insertion of a premature stop codon. According to the American College of Medical Genetics and Genomics, this mutation is described as a likely pathogenic-class 2 (PVS1_Very Strong). Conclusion: From analysis of previous literature, we concluded that the mutant sequence in exon 4 encodes the PEST region of the pioneer transcription factor PU.1, which is responsible for interaction with other transcription factors. Immunophenotyping of peripheral blood cells did not reveal CD19+ B cells, suggesting that a differentiation arrest may have developed between the prepro-B and pro-B stages, where there is a high requirement for PU.1 activity. Nextgeneration sequencing can be a very useful tool to uncover the causes of rare primary immunodeficiencies, but further analysis is needed to explain the relationship between patient genotype and clinical presentation

Effects of Levothyroxine Replacement Therapy on Parameters of Metabolic Syndrome and Atherosclerosis in Hypothyroid Patients: A Prospective Pilot Study

The aim of this study was to investigate the effect of levothyroxine (LT4) replacement therapy during three months on some parameters of metabolic syndrome and atherosclerosis in patients with increased thyroid-stimulating hormone (TSH) level. This study included a group of 30 female patients with TSH level GT 4mIU/L and 15 matched healthy controls. Intima media complex thickness (IMCT) and peak systolic flow velocity (PSFV) of superficial femoral artery were determined by Color Doppler scan. In hypothyroid subjects, BMI, SBP, DBP, and TSH were significantly increased versus controls and decreased after LT4 administration. FT4 was significantly lower in hypothyroid subjects compared with controls and significantly higher by treatment. TC, Tg, HDLC, and LDL-C were similar to controls at baseline but TC and LDL-C were significantly decreased by LH4 treatment. IMCT was significantly increased versus controls at baseline and significantly reduced by treatment. PSFV was similar to controls at baseline and significantly decreased on treatment. In this study, we have demonstrated the effects of LT4 replacement therapy during three months of treatment on correction of risk factors of metabolic syndrome and atherosclerosis