Pub Date : 2018-10-15DOI: 10.2298/HEMIND180327017S
Dunja Sokolovic, S. M. Hadnadjev-Kostic, Arpad Kiralj, R. M. S. Sokolović
Bed coalescers are compact, easy to install, automate, and maintain with the ability to achieve high separation efficiencies. They have been increasingly applied in the industry even though their design often requires pilot plant experiments. In this paper, a new wetting property of polymer fibers regarding polar mineral oils was established. This property can be important for selection of filter media for liquid-liquid separation in many industrial applications. Medical oil was selected as the new reference liquid that does not wet the investigated polymers. The lipophilic/lyophobic ratio (LLR) reached values ranging from 3.28 to 18.81 and increased with the increase of the mineral oil polarity measured by the oil neutralization number. The LLR values were in an excellent agreement with the results obtained from the separation efficiency of a steady-state bed coalescer. Thus, simple, fast and inexpensive experiments can replace pilot plant or at least laboratory testing aiming at selecting a polymer for oil separation from wastewater.
{"title":"Prediction of oily water separation efficiency by fiber beds using a new filter media property","authors":"Dunja Sokolovic, S. M. Hadnadjev-Kostic, Arpad Kiralj, R. M. S. Sokolović","doi":"10.2298/HEMIND180327017S","DOIUrl":"https://doi.org/10.2298/HEMIND180327017S","url":null,"abstract":"Bed coalescers are compact, easy to install, automate, and maintain with the ability to achieve high separation efficiencies. They have been increasingly applied in the industry even though their design often requires pilot plant experiments. In this paper, a new wetting property of polymer fibers regarding polar mineral oils was established. This property can be important for selection of filter media for liquid-liquid separation in many industrial applications. Medical oil was selected as the new reference liquid that does not wet the investigated polymers. The lipophilic/lyophobic ratio (LLR) reached values ranging from 3.28 to 18.81 and increased with the increase of the mineral oil polarity measured by the oil neutralization number. The LLR values were in an excellent agreement with the results obtained from the separation efficiency of a steady-state bed coalescer. Thus, simple, fast and inexpensive experiments can replace pilot plant or at least laboratory testing aiming at selecting a polymer for oil separation from wastewater.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"253-264"},"PeriodicalIF":0.9,"publicationDate":"2018-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42004871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-10-15DOI: 10.2298/HEMIND171121019E
Salem Embiriekah, M. Bulatović, M. Gnjatovic, M. Vukasinovic-Sekulic, Tanja Krunic, D. Zarić, Marica Rakin
The aim of this study was to examine the bioactive potential of hydrolysate powders produced by enzymatic and microbial hydrolysis of whey proteins followed by spray drying, in order to reveal which one of these processes result in a product with significantly improved functional properties. Hydrolysate powders produced by the two different biotechnological processes were compared based on their antioxidant (DPPH and FTC), antibacterial as well as erythrocyte membrane stabilizing activities. The performed tests revealed that the concentration of at least 178.4 mg mL -1 of the whey protein hydrolysate powder, produced by tryptic digestion, could inhibit the process of lipid peroxidation by 50 %, suppress the microbial contamination caused by S. aureus ATCC25923, B. cereus ATCC 11778 and L. monocytogenes , and provide the antioxidant and membrane stabilizing activities greater than 50 %. On the other hand, the hydrolysate powder obtained by whey fermentation at the concentration of at least 811.5 mg mL -1 achieved 50 % of all tested bioactivities, with the emphasis on the significantly more pronounced antibacterial activity against all tested strains. In that sense, tryptic hydrolysis could be highlighted as an optimal process that provides production of the whey hydrolysate with pronounced bioactive properties that could be considered as a very promising natural food supplement.
{"title":"Comparative analysis of functionality of spray dried whey protein hydrolysates obtained by enzymatic and microbial hydrolysis","authors":"Salem Embiriekah, M. Bulatović, M. Gnjatovic, M. Vukasinovic-Sekulic, Tanja Krunic, D. Zarić, Marica Rakin","doi":"10.2298/HEMIND171121019E","DOIUrl":"https://doi.org/10.2298/HEMIND171121019E","url":null,"abstract":"The aim of this study was to examine the bioactive potential of hydrolysate powders produced by enzymatic and microbial hydrolysis of whey proteins followed by spray drying, in order to reveal which one of these processes result in a product with significantly improved functional properties. Hydrolysate powders produced by the two different biotechnological processes were compared based on their antioxidant (DPPH and FTC), antibacterial as well as erythrocyte membrane stabilizing activities. The performed tests revealed that the concentration of at least 178.4 mg mL -1 of the whey protein hydrolysate powder, produced by tryptic digestion, could inhibit the process of lipid peroxidation by 50 %, suppress the microbial contamination caused by S. aureus ATCC25923, B. cereus ATCC 11778 and L. monocytogenes , and provide the antioxidant and membrane stabilizing activities greater than 50 %. On the other hand, the hydrolysate powder obtained by whey fermentation at the concentration of at least 811.5 mg mL -1 achieved 50 % of all tested bioactivities, with the emphasis on the significantly more pronounced antibacterial activity against all tested strains. In that sense, tryptic hydrolysis could be highlighted as an optimal process that provides production of the whey hydrolysate with pronounced bioactive properties that could be considered as a very promising natural food supplement.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"265-274"},"PeriodicalIF":0.9,"publicationDate":"2018-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49239966","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-10-15DOI: 10.2298/HEMIND171224015P
Emilija T. Pecev-Marinković, Z. Grahovac, A. Pavlović, S. Tošić, I. R. Mišić, M. Mitić, Ana S. Miletić, D. Sejmanović
A kinetic spectrophotometric method for determining residues of insecticide diflubenzuron 1(4-chlorphenyl)-3-(2,6-diflubenzoyl)urea (DFB) has been developed and validated. Kinetic method was based on the inhibitory effect of DFB on the oxidation reaction of sulfanilic acid (SA) by hydrogen peroxide in the presence of Co 2+ ions in a phosphate buffer, which was monitored at 370 nm. DFB can be measured in the concentration interval 0.102 – 3.40 μg mL -1 and 3.40 – 23.80 μg mL -1 . The detection and quantification limits of the method were calculated according to the 3σ criteria and found to be 0.077 μg mL -1 and 0.254 μg Ml ‑1 , respectively. The relative standard deviations for five replicate determinations of 0.102, 1.70 and 3.40 μg mL -1 DFB were 2.08, 1.22 and 1.21 %, respectively, for the first concentration interval, and the recovery percentage values were from 94.12 to 97.35 %. HPLC method was used as a parallel method to verify results of the kinetic method. The kinetic method was successfully applied to determine diflubenzuron concentrations in spiked water and baby food samples after solid phase extraction of the samples. The F and t values at 95% confidence level are lower than the theoretical ones, confirming agreement of the developed and the HPLC method.
建立了一种动态分光光度法测定杀虫剂二氟苯脲残留量的方法，并进行了验证。动力学方法基于DFB对磷酸缓冲液中Co 2+存在下过氧化氢氧化磺胺酸(SA)的抑制作用，并在370 nm处进行监测。DFB在0.102 ~ 3.40 μg mL -1和3.40 ~ 23.80 μg mL -1浓度范围内均可测定。根据3σ标准计算该方法的检出限和定量限分别为0.077 μg mL -1和0.254 μg mL -1。0.102、1.70、3.40 μg mL -1 DFB 5次重复测定在第一个浓度区间的相对标准偏差分别为2.08、1.22、1.21%，回收率为94.12 ~ 97.35%。以高效液相色谱法作为平行方法，对动力学方法的结果进行验证。采用固相萃取法测定了加标水和婴儿食品样品中的双氟苯脲浓度。在95%置信水平下，F和t值低于理论值，证实了所建立方法和HPLC方法的一致性。
{"title":"Development of a kinetic spectrophotometric method for insecticide diflubenzuron determination in water and baby food samples","authors":"Emilija T. Pecev-Marinković, Z. Grahovac, A. Pavlović, S. Tošić, I. R. Mišić, M. Mitić, Ana S. Miletić, D. Sejmanović","doi":"10.2298/HEMIND171224015P","DOIUrl":"https://doi.org/10.2298/HEMIND171224015P","url":null,"abstract":"A kinetic spectrophotometric method for determining residues of insecticide diflubenzuron 1(4-chlorphenyl)-3-(2,6-diflubenzoyl)urea (DFB) has been developed and validated. Kinetic method was based on the inhibitory effect of DFB on the oxidation reaction of sulfanilic acid (SA) by hydrogen peroxide in the presence of Co 2+ ions in a phosphate buffer, which was monitored at 370 nm. DFB can be measured in the concentration interval 0.102 – 3.40 μg mL -1 and 3.40 – 23.80 μg mL -1 . The detection and quantification limits of the method were calculated according to the 3σ criteria and found to be 0.077 μg mL -1 and 0.254 μg Ml ‑1 , respectively. The relative standard deviations for five replicate determinations of 0.102, 1.70 and 3.40 μg mL -1 DFB were 2.08, 1.22 and 1.21 %, respectively, for the first concentration interval, and the recovery percentage values were from 94.12 to 97.35 %. HPLC method was used as a parallel method to verify results of the kinetic method. The kinetic method was successfully applied to determine diflubenzuron concentrations in spiked water and baby food samples after solid phase extraction of the samples. The F and t values at 95% confidence level are lower than the theoretical ones, confirming agreement of the developed and the HPLC method.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"305-314"},"PeriodicalIF":0.9,"publicationDate":"2018-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47836517","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-30DOI: 10.2298/HEMIND171009006G
T. Golubović, A. Sedmak, V. S. Brkic, S. Kirin, E. Veg
Welded joints are analysed as critical regions in a pressure vessel in respect to structural failure due to the elastic-plastic fracture/crack growth. To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl-chloride monomer (VCM) storage tank in HIP Azotara Pancevo. The risk matrix has been used, taking into account the basic definition of risk, being the product of the probability and consequence, and applied to different regions of welded joints, having different mechanical properties, i.e. crack resistance. To estimate probability, the failure assessment diagram (FAD) has been used, as an engineering tool, defined according to the position of the operating point for different regions of the welded joint, relative to the critical point on the limit curve. Generally speaking, consequence is estimated based on pressure vessel parameters, or by detailed analysis of health, safety, business and security issues, but in the analysed case, the worst case scenario is assumed, with the highest consequence due to potential disaster for environment and fatalities.
{"title":"Welded joints as critical regions in pressure vessels – case study of vinyl-chloride monomer storage tank","authors":"T. Golubović, A. Sedmak, V. S. Brkic, S. Kirin, E. Veg","doi":"10.2298/HEMIND171009006G","DOIUrl":"https://doi.org/10.2298/HEMIND171009006G","url":null,"abstract":"Welded joints are analysed as critical regions in a pressure vessel in respect to structural failure due to the elastic-plastic fracture/crack growth. To assess structural integrity of pressure vessels used in chemical industry the risk based procedure has been introduced and applied in the case of a large spherical pressure vessel used as a vinyl-chloride monomer (VCM) storage tank in HIP Azotara Pancevo. The risk matrix has been used, taking into account the basic definition of risk, being the product of the probability and consequence, and applied to different regions of welded joints, having different mechanical properties, i.e. crack resistance. To estimate probability, the failure assessment diagram (FAD) has been used, as an engineering tool, defined according to the position of the operating point for different regions of the welded joint, relative to the critical point on the limit curve. Generally speaking, consequence is estimated based on pressure vessel parameters, or by detailed analysis of health, safety, business and security issues, but in the analysed case, the worst case scenario is assumed, with the highest consequence due to potential disaster for environment and fatalities.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"177-182"},"PeriodicalIF":0.9,"publicationDate":"2018-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49293895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-30DOI: 10.2298/HEMIND180228012G
Branka Grujić, Z. Vuković, Jelena Veljković‐Giga, S. Ibrić, D. Dekanski
Nutrition and dietary supplements have a significant role in the prevention and treatment of cardiovascular disease. Olive and vine leaves, thanks to their constituents, represent powerful natural antioxidants exhibiting cardioprotective activity. High concentrations of active ingredients can be provided by means of extraction. Dry herbal extracts are highly sensitive to moisture and elevated temperature and from the pharmaceutical and technological point of view these are raw materials with inadequate technological properties. The aim of this study was to investigate and to compare the influence of different excipients in capsule formulation of these two dry extracts i.e. the selection of excipients that will ensure appropriate critical process parameters in the manufacturing procedure. The monitored quality characteristics include flowability, bulk density and tapped density that are critical for technological feasibility of the capsule-filling operation. The effects of excipients on the above parameters have been experimentally studied and the appropriate capsule formulations have been developed based on the obtained results, which will ensure homogeneity and stability of the preparation.
{"title":"An investigation into the effects of excipients on quality characteristics of a dry herbal extract containing capsule","authors":"Branka Grujić, Z. Vuković, Jelena Veljković‐Giga, S. Ibrić, D. Dekanski","doi":"10.2298/HEMIND180228012G","DOIUrl":"https://doi.org/10.2298/HEMIND180228012G","url":null,"abstract":"Nutrition and dietary supplements have a significant role in the prevention and treatment of cardiovascular disease. Olive and vine leaves, thanks to their constituents, represent powerful natural antioxidants exhibiting cardioprotective activity. High concentrations of active ingredients can be provided by means of extraction. Dry herbal extracts are highly sensitive to moisture and elevated temperature and from the pharmaceutical and technological point of view these are raw materials with inadequate technological properties. The aim of this study was to investigate and to compare the influence of different excipients in capsule formulation of these two dry extracts i.e. the selection of excipients that will ensure appropriate critical process parameters in the manufacturing procedure. The monitored quality characteristics include flowability, bulk density and tapped density that are critical for technological feasibility of the capsule-filling operation. The effects of excipients on the above parameters have been experimentally studied and the appropriate capsule formulations have been developed based on the obtained results, which will ensure homogeneity and stability of the preparation.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"183-189"},"PeriodicalIF":0.9,"publicationDate":"2018-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42774192","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-07-30DOI: 10.2298/10.2298/HEMIND180515016D
Александар Б. Декански, Владимир В. Панић
Кроз преглед принципа рада уређаја за динамичко складиштење енергије и њихове најновије генерације, електрохемијских суперкондензатора, као и компоненти и активних материјала који се користе за њихову израду и опис различитих приступа изради, изложено је тренутно стање у развоју истраживања суперкондензатора као важног сегмента склопова за алтернативно напајање електричном енергијом. Дискутоване су њихове предности и недостаци у односу на друге врсте електрохемијских извора струје, пре свега батерија.
{"title":"Електрохемијски суперкондензатори: Принцип рада, компоненте и активни материјали","authors":"Александар Б. Декански, Владимир В. Панић","doi":"10.2298/10.2298/HEMIND180515016D","DOIUrl":"https://doi.org/10.2298/10.2298/HEMIND180515016D","url":null,"abstract":"Кроз преглед принципа рада уређаја за динамичко складиштење енергије и њихове најновије генерације, електрохемијских суперкондензатора, као и компоненти и активних материјала који се користе за њихову израду и опис различитих приступа изради, изложено је тренутно стање у развоју истраживања суперкондензатора као важног сегмента склопова за алтернативно напајање електричном енергијом. Дискутоване су њихове предности и недостаци у односу на друге врсте електрохемијских извора струје, пре свега батерија.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"229-251"},"PeriodicalIF":0.9,"publicationDate":"2018-07-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41375568","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-05DOI: 10.2298/HEMIND170924004M
Aleksandra Mitrović, B. Bojovic, D. Stamenković, Dejana Popović
The aim of this work was to develop new soft contact lens (SCL) materials which would, after recommended and existing machining processes, improve surface roughness. Nanomaterials were incorporated into commercial material for SCL (SL38) based on PHEMA, which were derived by the technology in the production lab of the company Soleko (Milan, Italy). Nanophotonic SCLs (SL38-A, SL38-B, SL38-C) were produced in the company Optix (Belgrade, Serbia) from the obtained materials. For the surface characterization of SCLs, AFM analysis and lacunarity method were performed. The results showed that SL38-B average roughness value is lower than SL38-A and SL38. The topography parameters of SL38-C were between the parameters of SL38-A and SL38-B. Lacunarity analysis of AFM images confirmed that SCLs surface state should belong to either group of adequate (slanted p -diagram) or inadequate (contorted p -diagram) roughness concerning tear film stability. Nanophotonic SCL SL38-C evince more acceptable performance consider SCL surface functional behavior compare other SCLs. The positive result of incorporating nanomaterials into basic material for SCL is better quality of the nanophotonic SCLs surfaces. On the bases of these experiments, the assumption that incorporation of fullerene derivate can play a role in the prevention of a significant increase in roughness is confirmed.
{"title":"Characterization of surface roughness of new nanophotonic soft contact lenses using lacunarity and AFM method","authors":"Aleksandra Mitrović, B. Bojovic, D. Stamenković, Dejana Popović","doi":"10.2298/HEMIND170924004M","DOIUrl":"https://doi.org/10.2298/HEMIND170924004M","url":null,"abstract":"The aim of this work was to develop new soft contact lens (SCL) materials which would, after recommended and existing machining processes, improve surface roughness. Nanomaterials were incorporated into commercial material for SCL (SL38) based on PHEMA, which were derived by the technology in the production lab of the company Soleko (Milan, Italy). Nanophotonic SCLs (SL38-A, SL38-B, SL38-C) were produced in the company Optix (Belgrade, Serbia) from the obtained materials. For the surface characterization of SCLs, AFM analysis and lacunarity method were performed. The results showed that SL38-B average roughness value is lower than SL38-A and SL38. The topography parameters of SL38-C were between the parameters of SL38-A and SL38-B. Lacunarity analysis of AFM images confirmed that SCLs surface state should belong to either group of adequate (slanted p -diagram) or inadequate (contorted p -diagram) roughness concerning tear film stability. Nanophotonic SCL SL38-C evince more acceptable performance consider SCL surface functional behavior compare other SCLs. The positive result of incorporating nanomaterials into basic material for SCL is better quality of the nanophotonic SCLs surfaces. On the bases of these experiments, the assumption that incorporation of fullerene derivate can play a role in the prevention of a significant increase in roughness is confirmed.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"157-166"},"PeriodicalIF":0.9,"publicationDate":"2018-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47090035","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-05DOI: 10.2298/HEMIND170928005M
A. Maslarevic, M. Bakic, B. M. Djukic, B. Rajicic, Vesna Maksimovic
Delovi masina i konstrukcija su tokom rada izloženi delovanju agresivne radne sredine koja u kratkom vremenskom periodu može da narusi njihov integritet. U zavisnosti od radnih uslova, povrsina materijala može da bude izložena raznim mehanizmima ostecenja, od kojih se izdvajaju eroziona i koroziona ostecenja. Produžetak radnog veka ugroženih zona masinskih konstrukcija moguce je izvesti razlicitim postupcima nanosenja zastitnih prevlaka, a najcesce su to razliciti postupci navarivanja i metalizacije. Cilj ovog rada je karakterizacija prevlake izrađene od nerđajuceg celika klase 316L, koja je nasla siroku primenu u hemijskoj i petrohemijskoj industriji, nanete plazma postupkom navarivanja koriscenjem dodatnog materijala u obliku praha, na konstrukcioni celik S235JR. U radu je izvrseno merenje tvrdoce u karakteristicnim zonama prevlake i osnovnog materijala, kao i mikrostrukturna karakterizacija prevlake na optickom i skenirajucem elektronskom mikroskopu. Takođe, izvrseno je eroziono ispitivanje prevlake promenom osnovnih uticajnih parametara ispitivanja, pre svega ugla nastrujavanja i brzine cestica erodenta.
{"title":"Characterization of a coating 316L applied by plasma transferred arc","authors":"A. Maslarevic, M. Bakic, B. M. Djukic, B. Rajicic, Vesna Maksimovic","doi":"10.2298/HEMIND170928005M","DOIUrl":"https://doi.org/10.2298/HEMIND170928005M","url":null,"abstract":"Delovi masina i konstrukcija su tokom rada izloženi delovanju agresivne radne sredine koja u kratkom vremenskom periodu može da narusi njihov integritet. U zavisnosti od radnih uslova, povrsina materijala može da bude izložena raznim mehanizmima ostecenja, od kojih se izdvajaju eroziona i koroziona ostecenja. Produžetak radnog veka ugroženih zona masinskih konstrukcija moguce je izvesti razlicitim postupcima nanosenja zastitnih prevlaka, a najcesce su to razliciti postupci navarivanja i metalizacije. Cilj ovog rada je karakterizacija prevlake izrađene od nerđajuceg celika klase 316L, koja je nasla siroku primenu u hemijskoj i petrohemijskoj industriji, nanete plazma postupkom navarivanja koriscenjem dodatnog materijala u obliku praha, na konstrukcioni celik S235JR. U radu je izvrseno merenje tvrdoce u karakteristicnim zonama prevlake i osnovnog materijala, kao i mikrostrukturna karakterizacija prevlake na optickom i skenirajucem elektronskom mikroskopu. Takođe, izvrseno je eroziono ispitivanje prevlake promenom osnovnih uticajnih parametara ispitivanja, pre svega ugla nastrujavanja i brzine cestica erodenta.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"139-147"},"PeriodicalIF":0.9,"publicationDate":"2018-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43953751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-05DOI: 10.2298/HEMIND170924008K
M. Kostić, L. Nikolić, V. Nikolić, Dušan Petković, M. Igić, N. Krunić, M. Manić, N. Gligorijević, G. Radenković
Acrylic restorations in the mouth are exposed to strong occlusal forces. Their mechanical properties depend on the type and method of their polymerization. The aim of this study is a comparative analysis of mechanical properties (flexural strength and modulus of elasticity) of acrylic materials before and after the post-polymerization treatments (water boiling, microwave irradiation and water storage). The study included denture base resins, as well as an acrylate for orthodontic appliances impregnated with aesthetic beads. Flexural strength, modulus of elasticity and the deflection were measured immediately after polymerization, after a hot and microwave post-polymerization and after immersion in a water bath at the temperature of 37 °C. The applied post-polymerization methods resulted in an increase in flexural strength and modulus of elasticity relative to the initial values for all tested materials. Being aware of the reduction in fracture risk of dental prosthesis after a proposed post-polymerization procedure, it could be used in all clinical situations where there is an increased risk of damage to dentures.
{"title":"Effects of water boiling, microwave, and water bath post-polymerization on mechanical properties of acrylic denture resins","authors":"M. Kostić, L. Nikolić, V. Nikolić, Dušan Petković, M. Igić, N. Krunić, M. Manić, N. Gligorijević, G. Radenković","doi":"10.2298/HEMIND170924008K","DOIUrl":"https://doi.org/10.2298/HEMIND170924008K","url":null,"abstract":"Acrylic restorations in the mouth are exposed to strong occlusal forces. Their mechanical properties depend on the type and method of their polymerization. The aim of this study is a comparative analysis of mechanical properties (flexural strength and modulus of elasticity) of acrylic materials before and after the post-polymerization treatments (water boiling, microwave irradiation and water storage). The study included denture base resins, as well as an acrylate for orthodontic appliances impregnated with aesthetic beads. Flexural strength, modulus of elasticity and the deflection were measured immediately after polymerization, after a hot and microwave post-polymerization and after immersion in a water bath at the temperature of 37 °C. The applied post-polymerization methods resulted in an increase in flexural strength and modulus of elasticity relative to the initial values for all tested materials. Being aware of the reduction in fracture risk of dental prosthesis after a proposed post-polymerization procedure, it could be used in all clinical situations where there is an increased risk of damage to dentures.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"129-137"},"PeriodicalIF":0.9,"publicationDate":"2018-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41560037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2018-06-05DOI: 10.2298/HEMIND170529007D
Ljubiša Dubonjić, V. Filipovic, N. Nedic, Vladimir Đorđević
H ¥ control theory has achieved a very high level, which is not followed by appropriate application in industry. Some reasons are: synthesis of H ¥ controllers is complex and based on the numerical Nevanlinna-Pick procedure, high order of controllers (higher than the order of the process) and sensitivity to deviation of controller coefficients (fragile controller). On the other hand, PI (PID) controllers are still dominant in industry, which places the problem of design of fixed structure controllers at the forefront. The mentioned problem is very difficult. This paper proposes a simple interactive procedure for design of H ¥ PI controllers with the presence of constraints (given relative stability) based on D-decomposition. The catalogue of responses to references, suppression of disturbances and minimum of H ¥ criteria of control is created. The selection of controllers, based on the catalogue, is left to the user. The application of H ¥ PI controllers to a CSTR (continuous stirred-tank reactor) is demonstrated.
{"title":"Design of an H(lemniscate) PI controller with given relative stability and its application to the CSTR problem","authors":"Ljubiša Dubonjić, V. Filipovic, N. Nedic, Vladimir Đorđević","doi":"10.2298/HEMIND170529007D","DOIUrl":"https://doi.org/10.2298/HEMIND170529007D","url":null,"abstract":"H ¥ control theory has achieved a very high level, which is not followed by appropriate application in industry. Some reasons are: synthesis of H ¥ controllers is complex and based on the numerical Nevanlinna-Pick procedure, high order of controllers (higher than the order of the process) and sensitivity to deviation of controller coefficients (fragile controller). On the other hand, PI (PID) controllers are still dominant in industry, which places the problem of design of fixed structure controllers at the forefront. The mentioned problem is very difficult. This paper proposes a simple interactive procedure for design of H ¥ PI controllers with the presence of constraints (given relative stability) based on D-decomposition. The catalogue of responses to references, suppression of disturbances and minimum of H ¥ criteria of control is created. The selection of controllers, based on the catalogue, is left to the user. The application of H ¥ PI controllers to a CSTR (continuous stirred-tank reactor) is demonstrated.","PeriodicalId":12913,"journal":{"name":"Hemijska Industrija","volume":"72 1","pages":"115-127"},"PeriodicalIF":0.9,"publicationDate":"2018-06-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45390864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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