Predetermined Proportions Research Articles

COMPARATIVE EFFECT OF WOODFLOUR AND GRANULATED RICE HUSK ON THE THERMAL INSULATION OF TERMITE HILL CLAY

This research work covered the comparative effect of wood flour (saw dust) and granulated rice husk on the thermal insulation of termite hill clay. The raw clay samples were mined from the Federal University of Technology Akure Campus and processed. Likewise, the saw dust and rice husk were also processed and grinded. The clay samples and the additives were sieved to obtain 300 microns and were mixed in predetermined proportions of 0, 2, 4, 6, 8 and 10 wt. %. Cylindrical samples were developed from the mixtures which were compacted and then air dried before oven dried and finally fired. The fired samples were subjected to selected tests to determine their insulation and refractory properties. These tests include porosity, linear shrinkage, volumetric shrinkage, bulk density, thermalconductivity, thermal shock resistance and cold crushing tests. It was discovered that the saw dust samples meet the ASTM standard for insulating bricks while the rice husk samples did not. Saw dust samples with 2 and 8 wt. % were ones with optimum properties.

Evaluating German PISA stratification designs: a simulation study

Stratification is an important design feature of many studies using complex sampling designs and it is often used in large-scale assessment (LSA) studies, such as the Programme for International Student Assessment (PISA), for two main reasons. First, stratification variables that achieve a high between and low within strata variance can improve the efficiency of a survey design. Second, stratification allows one to, explicitly or implicitly, control for sample sizes across subpopulations. It ensures that some parts of a population are in the sample in predetermined proportions. In this study, we determine through simulation which stratification scheme is best for PISA in Germany. For this, we consider the constraints imposed by the international sampling design, the available information about schools, and specific national characteristics of the German educational system. We examine seven different stratification designs selected based on scenarios used in past LSAs in Germany and theoretical considerations for future implementations. The chosen scenarios were compared with two reference scenarios: (1) an unstratified design and (2) a synthetic optimal stratification design. The simulation study reveals that the stratification design currently applied in PISA produces satisfactory results regarding sampling precision. The present stratification design is based on Germany's federal states and school types. However, this approach leads to small strata, which has been problematic for estimating sampling variance in previous cycles. Therefore, alternative stratification scenarios were considered and, in addition to overcoming the small-strata problem, also led to smaller standard errors for estimates of student mean performance in mathematics, science, and reading. As a result of this study, we recommend considering three different stratification designs for Germany in future cycles of PISA. These recommendations aim to: (1) improve the sampling efficiency while keeping the sample size constant, (2) follow a sound methodological approach, and (3) make conservative and cautious changes while maintaining a reflection of the structure of the German federal school system with different school types. These suggestions include a reinvented stratification of grouped German federal states and designs with school types as explicit stratifiers and federal states as implicit stratifiers.

Influence of quartz and marble on the performance of particulate-filled rigid polyurethane foams

This work was carried out to investigate the roles of quartz and marble on the performance of polyurethane particulate-filled composites. Prior to the mixing, the quartz and marble were pulverized and sieved to obtain an average particle size of less than 90 µm. Polyurethane (PU) was produced from isocyanate and polyol by a two-step method in which marble and quartz particles were incorporated in predetermined proportions. Three different weight ratios were utilized to investigate the physical, chemical, and mechanical behavior of the pristine rigid polyurethane foam (RPUF) and the marble and quartz-filled RPUF using analytical equipment such as FTIR, XRF, and SEM. The mechanical properties were performed according to the ASTM standards, where the compressive and flexural strengths were investigated using the universal testing machine. Overall, the RPUF shows the hydroxyl bands, while the principal elements of fillers are Calcium and Silicon. It was discovered from the results that adding these fillers improved the mechanical properties of the filled samples, where the compressive strength was enhanced.

The Impact of Remuneration as Reward System on Job Satisfaction within the Hospitality Industries in Ghana

This research used a qualitative study method which is to draw analysis from inductive angles. It has the following objectives as first to determine the impact of remuneration has on job satisfaction of employees, secondly, to further understand whether there is equity in remuneration policies that are applied to employees in general, and thirdly, to establish other remuneration systems that exists in most hospitality pay policies. The aim of this research is to assess the impact of remuneration and job satisfaction among hotel workers, there is the need to gather data on remuneration and job satisfaction of hospitality service in Ghana. This is an inductive study based on non-probability sampling technique. A quota sampling of 50 AH Hotel workers responded to the questionnaire. Quota sampling is a non-probability sampling method that relies on the non-random selection or convenience of a predetermined number or proportion of units. The research designed closed ended and open questions in the interview questionnaire (as data collection instrument in qualitative nature) which the respondents gave their feedback. The research findings shows that remuneration payment has greater impact on job satisfaction because many of the employees were happy with their salaries/wages. This is the more reason why they are retained as loyal staff with good morale behaviours, punctuality at work, and are also, good team players.

Cubosomes as versatile lipid nanocarriers for neurological disorder therapeutics: a comprehensive review.

Cubosomes are novel vesicular drug delivery systems with lipidic liquid crystal nanoparticles formed of predetermined proportions of amphiphilic lipids. They have a honeycomb-like structure and are thermodynamically stable. These bicontinuous lipid layers are separated into two water-based channels internally that can be used by various bioactive substances, including drugs, proteins, and peptides. This complex structure is responsible for its high drug-loading capacity. Cubosomes are thought to be promising vehicles for various routes of administration because of their extraordinary characteristics, including bioadhesion, the capacity to encapsulate hydrophilic, and hydrophobic, as well as amphiphilic substances, high resistance to environmental stress, and their ability to achieve controlled release through modification. One of the essential elements for improving patient compliance is the ability of these well-defined nano-drug delivery systems to boost the effectiveness of targeting while lowering the side effects/toxicities of payloads. The large internal surface area, a sufficiently uncomplicated fabrication procedure, and biodegradability make it an attractive nano lipid carrier for drug delivery. This review outlines the recent advancement of cubosomes for managing various neurological disorders, highlighting their potential in this field.

Effects of fine aggregate content on the unsaturated hydraulic characteristics of recycled concrete aggregate

Recycled concrete aggregate (RCA) can be used in landfill and slope cover systems, where its unsaturated hydraulic properties play an important role. The hydraulic behavior of RCAs can be potentially controlled through mixing coarse and fine aggregates by a pre-determined proportion, which lacks experimental validation. In this study, water retention curve (WRC) and permeability function (PF) of RCAs with different fine aggregate contents ( fc) were investigated. Experiments on 9 RCAs with different gradations reveal that when fc is between 20% and 30%, a second air entry value appears, and the shape of both WRC and PF becomes bimodal, which is probably resulted from an uneven dual-peak pore size distribution. With an increasing fc, the first air entry value and the residual water content increases. The unsaturated coefficient of permeability decreases with the increasing fc for a low suction level (<0.1 kPa), but increases with the raise of fc for high suction (>10 kPa). Overall, adopting a properly mixed RCA with fc value of less than 10% or over 40%, instead of a narrowly graded RCA, is recommended for coarse- and fine-grained layers in a capillary barrier, respectively.

Characterization of animal shells-derived hydroxyapatite reinforced epoxy bio-composites

Environmental issues have geared the interest of researchers toward the use of naturally occurring materials for various applications in recent times. Hydroxyapatite particles (HAp) for biomedical applications were synthesized from egg and snail shells and used for the fabrication of bio-composites in this research. The shells were prepared by thoroughly cleaning before subjecting to calcination as well as wet-chemical precipitation treatment to obtain 50 µ sized hydroxyapatite particles that were used for the development of the bio-composites. The composites were fabricated with an open mold stir casting technique after mixing the constituents in predetermined proportions. Mechanical, wear, and physical properties evaluations were carried out on the composites and control samples while the images of the fractured surfaces were examined using a scanning electron microscope. It was revealed from the results that the addition of hydroxyapatite to epoxy improved the properties of the composite where most of the optimal values emerged from 15 wt% HAp-reinforced samples. It was discovered that snail shell HAp-based composites had superior enhancements than the eggshell HAp-based composites which showed that the source of the animal shell influences the characteristics of the ensuing properties. Flexural strength and modulus were 63.95 and 774.64 MPa, respectively; hardness was 40.25 HS, wear index was 0.07, and thermal conductivity was 0.545 W/mK for the snail shell HAp-based composites. Hence, synthesized HAp from snail shells is more structurally stable than eggshell-based and can be used for biomedical applications.

Development and characterization of moringa oleifera fruit waste pod derived particulate cellulosic reinforced epoxy bio-composites for structural applications

The desire for environment-friendly materials and sustainability has brought a paradigm shift in the way engineers and the entire material research community thinks while attempting to develop new material, particularly for engineering applications. This study is carried out to underscore the suitability of particulate moringa oleifera fruit pod (MOFP) reinforced epoxy bio-composites on selected properties for structural applications. The dried waste fruit pods were processed as calcined and pulverized fruit pod particulates, respectively. Their respective bio-composites were developed by blending the selected materials in predetermined proportions using the open mould processing method. The MOFP particles were characterized with SEM/EDS and XRD while mechanical and wear properties of the developed bio-composites were evaluated. The results showed that the pulverized MOFP reinforced epoxy bio-composites showed improved properties than the calcined MOFP bio-composites in most of the properties considered. This was noticed to be due to the presence of more elemental constituents and at higher proportions in pulverized particles than in the calcined particles. It was discovered that 15 wt.% pulverized MOFP reinforced epoxy bio-composites gave about 67.9%, 28.7%, 8.8%, and 8.8% enhancement and with a value of 70.2 HS, 39.02 MPa, 198.4 MPa, and 753.28 MPa in hardness, flexural strength, flexural modulus, and tensile modulus, respectively to emerge as the reinforcement content with the optima properties. Based on the findings, MOFP particles reinforced epoxy-based biocomposites can be used in applications where stiffness and high strength are not essential requirements; packaging applications; in electrical component applications such as circuit boards, and cables due to their low thermal conductivity.

MICROSTRUCTURAL CHARACTERISATION, RHEOLOGICAL AND WATER ABSORPTION PROPERTIES OF FILLED POLYURETHANE FOAM

This work investigates the microstructural characterization, rheological and water absorption properties of granite and feldspar filled polyurethane foam. Foaming of polyurethane with the use of synthetic materilas as suitable additives remain a major setback for polyurethane foams. Hence, granite and feldspar are selected as the fillers, pulverized and sieved to ˂90 µm and are randomly dispersed into the polyurethane matrix. The matrix constituents were mixed in the same ratio while fillers were introduced via a one-shot system approach in predetermined proportions of 3-7 wt%. The work was carried out to identify optimum fillers to be utilized in the production of rigid polyurethane foams given the effect of the fillers on the microstructural characterisation, rheological and water absorption properties of the foams. SEM, XRF and FTIR analysis were used characterize the foams while rheological and water absorption tests are also carried out. The presence of the fillers in the foam showed a rupture in the structure of the foams with the cells having similar arrangements. The cream, gel, rise, and the tack-free time was delayed with the presence of the filler particles. It was discovered that 7 wt% feldspar addition enhances the cream and gel time while 3 wt% granite enhance rise and tack free time, respectively in the optima conditions. It was discovered that the two fillers had inverse effects on the rheological properties. The addition of granite and feldspar degrades the sulfonic acid groups and promoted the appearance of Si-O stretching vibration band

How cooperative advertising interacts with distributional contracts in a dual-channel system

With the development of E-commerce, an increasing number of online platforms are conducting advertising campaigns to expand their sales. In some situations, the manufacturer is willing to share the advertising cost, while in others it is not. Additionally, recently, many online platforms have started choosing an agency contract, instead of a wholesale contract, to obtain a predetermined proportion of revenue from the manufacturer to make profits. This paper studies a scenario of a manufacturer selling through both a direct channel and a platform channel to investigate the interaction between a manufacturer’s cooperative advertising strategy and a platform’s distribution contract choice. We develop a stylized model based on game theory to drive the optimal prices and advertising level under different contracts. By using a representative consumer function, we drive the following interesting results. Firstly, under the wholesale contract, a manufacturer prefers cooperating only when the cost-sharing rate is small, but under an agency contract, when the revenue-sharing rate is large, the manufacturer will not choose to cooperate even if the cost-sharing rate is low. Secondly, the platform’s profit does not always increase in the revenue-sharing rate. Finally, under some conditions, the platform would prefer that the manufacturer not share the cost. Specifically, when the competition intensity is small and the revenue-share rate is high, the platform would rather choose an agency contract to cover all advertising costs on its own than a wholesale contract where the manufacturer is willing to share advertising costs. We also consider direct channel advertising as well in an extension, and the qualitative results still hold.

Performance of Fly Ash as Replacement for Non-Renewable Constituent in Asphaltic Concrete for Road Development

The non-renewable constituent used in asphalt concrete consumed large amount of materials resulting an increase in the price of asphalt mixture and consequently the cost of road development. On the other hand, huge industrial waste being generated daily from human activities causes environmental degradations. Thus, the study evaluates the performance of fly ash (FA) in asphalt concrete development targeted for road application. The aggregate, bitumen, and fly ash were characterized before being used. The stone dust in asphalt mixture was replaced with FA in predetermined proportions of 2, 4, 6, and 8% to produce a cylindrical specimen of asphalt mixture concrete. Marshal stability test, flow test, X-ray diffraction (XRD), X-ray Fluorescence (XRF) and Scanning Electron Microscope (SEM) was conducted on the composite samples. From the results, stability values of 7.39, 7.70, 7.90 and 8.22 KN was obtained at 2, 4, 6 and 8% replacements, respectively. Hence, the optimum value of 8.22 KN obtained from 8% partial replacement with FA is adequate for heavy traffic while other partial replacement from 2- 6% with stability within the range of 7.39-7.90 KN is suitable for medium traffic in accordance with the criteria for the marshal mix design method provided by Asphalt institute (1997). Corresponding values of 3.7, 3.5, 3.3 and 3.0 mm was obtained for the flow. The flow, air void, void in mineral aggregates and void filled with bitumen results all satisfied Nigeria general specification for road and bridges (1997). Therefore, fly ash can be used as partial replacement in asphaltic concrete to enhance the performance of the mix with a reduced cost for pavement construction.

Strength and durability of flyash, GGBS and cement clinker stabilized dispersive soil

Dispersive soils are highly susceptible to erosion due to higher sodium content, and it deflocculates in the presence of flowing water. Under saturated conditions, the attractive forces are less than the repulsive forces, and this will help the particle to segregate and to move in suspension. In this investigation, an attempt has been made to stabilize the dispersive soil with cement clinker, ground granulated blast furnace slag (GGBS) and flyash. Samples were prepared with the different predetermined proportions of dispersive soil, cement clinker, GGBS, and fly ash to determine the strength and durability of the stabilized soils. Results of unconfined compressive strength (UCS) are found to be increased significantly by mixing additives in different proportions. From the results of the UCS tests, the optimum mix proportion was obtained with the mixing of 20% of flyash, 15% of GGBS and 30% of cement clinker in dispersive soil. Outcomes of this study suggest that the combined mixture of cement clinker, flyash, and GGBS are more effective to improve the strength than an alone mix. To evaluate the effect of freeze-thaw cycles and water immersion aging on the strength properties of different mix proportion, 0, 1, 3, 6, 9 and 12 cycles freeze-thaw tests and 32 days water immersion tests were done on cylindrical samples at 7, 14, 28, 60 and 90 days curing periods. A coefficient of strength loss/gain was also defined to determine the influence of freezing-thawing and water immersion aging on the durability of the mix proportion. The X-raydiffraction tests (XRD) divulge the formation of hydrated particles play a vital role to enhance the strength because of the reaction between the soil and the additives.

Development of nanostructured bioplastic material for wound healing

The development of new biomaterials whose characteristics are as close as possible to the properties of living human tissues is one of the most promising areas of regenerative medicine. This work aimed at creating a bioplastic material based on collagen, elastin and hyaluronic acid and studying its structure and properties to assess the prospects for further use in clinical practice. Bioplastic material was obtained by mixing collagen, hyaluronic acid and elastin in predetermined proportions with distilled water. We treated the material with photochemical crosslinking to stabilize biofilm in a liquid medium and form a nanostructured scaffold. A commercial human skin fibroblast cell culture was used to assess the biomaterial cytotoxicity and biocompatibility. The visualization and studies of the biomaterial structure were performed using light and scanning electron microscopy. It has been shown that the obtained biomaterial is characterized by high resilience; it has also a high porosity. The co-culturing of the bioplastic material and human fibroblasts did not reveal any of its cytotoxic effects on cells in culture. It was shown that the biomaterial samples could maintain physical properties in the culture medium for more than 10 days, while the destruction of the matrix was observed 3–4 weeks after the beginning of incubation. Thus, the created biomaterial can be used on damaged skin areas due to its physical properties and structure. The use of the developed biomaterial provides effective conditions for good cell proliferation, which allows us to consider it as a promising wound cover for use in clinical practice.

Development of nanostructured bioplastic material for wound healing.

The development of new biomaterials whose characteristics are as close as possible to the properties of living human tissues is one of the most promising areas of regenerative medicine. This work aimed at creating a bioplastic material based on collagen, elastin and hyaluronic acid and studying its structure and properties to assess the prospects for further use in clinical practice. Bioplastic material was obtained by mixing collagen, hyaluronic acid and elastin in predetermined proportions with distilled water. We treated the material with photochemical crosslinking to stabilize biofilm in a liquid medium and form a nanostructured scaffold. A commercial human skin fibroblast cell culture was used to assess the biomaterial cytotoxicity and biocompatibility. The visualization and studies of the biomaterial structure were performed using light and scanning electron microscopy. It has been shown that the obtained biomaterial is characterized by high resilience; it has also a high porosity. The co-culturing of the bioplastic material and human fibroblasts did not reveal any of its cytotoxic effects on cells in culture. It was shown that the biomaterial samples could maintain physical properties in the culture medium for more than 10 days, while the destruction of the matrix was observed 3–4 weeks after the beginning of incubation. Thus, the created biomaterial can be used on damaged skin areas due to its physical properties and structure. The use of the developed biomaterial provides effective conditions for good cell proliferation, which allows us to consider it as a promising wound cover for use in clinical practice.

Соочистка рекомбинантных модифицированных глюкагоноподобного и глюкозозависимого инсулинотропного пептидов для создания двухкомпонентного препарата для лечения сахарного диабета типа 2 и ожирения

In addition to the previously developed recombinant modified human glucagon-like peptide 1 (rmglp1, Glypin), a recombinant modified human glucose-dependent insulinotropic peptide (RMGIP) has been obtained. A new universal reverse-phase HPLC technique has been proposed allowing quantitative analysis of rmGlp1 and rmGip separately and as part of a two-component preparation. The data show that the design of recombinant human rmGip according to the Glypine formula makes it possible to produce one-component and two-component preparations containing various rmGip and rmGlp1 protein ratios ranging from 1:0 to 20:1, using cell biomass samples mixed in predetermined proportions. Studies of human rmGip activity in a mouse model revealed reduced specific activity and signs of weak antagonistic effects. In this regard, there is a need for further study of human rmGip activity in a mouse model, including the use of alternative mouse or rat rmGip. type 2 diabetes mellitus; two-component drug, glucose-dependent insulinotropic peptide, glucagon-like peptide-1 The work was supported by the Internal Grant from National Research Center Kurchatov Institute.

Comparative investigation of the influence of kaolin and dolomite on the properties of polyurethane foam

This work investigates the influence of kaolin and dolomite on the properties of polyurethane foam. The selected fillers were pulverized and sieved to obtained < 90 μm that were used as reinforcements in the polyurethane matrix in a randomly dispersed mode. The matrix constituents were mixed in the same ratio while fillers were introduced via a one-shot system approach in predetermined proportions of 3–7 wt.%. The work was carried out to identify optimum fillers to be utilized in the production of polyurethane rigid foams given the effect of the fillers on the physical, mechanical, and chemical properties of the foam. FTIR, XRF, and SEM and mechanical property tests were carried out on the filled polyurethane foam. The presence of the fillers in the foam showed a rupture in the structure of the foams with the cells having similar arrangements. The addition of dolomite and Kaolin degrades the sulfonic acid groups and promoted the appearance of Si–O stretching vibration band. The density, hardness, flexural and compressive strengths of the polyurethane foam were enhanced with the the addition of dolomite and kaolin particles.

Abrasion and Physical Properties of Rattan Cane (<i>Calamus deeratus</i>) Fibre Based Epoxy Composites

The effects of fibre content (5–30 wt%) and fibre treatment on abrasion, water absorption, specific gravity, and density properties of epoxy/rattan cane fibre composites were studied. Epoxy resin reinforced with the alkaline treated rattan cane fibre fibres was produced by compression technique in predetermined proportions. Abrasion and physical properties tests were carried out on the developed composites. The results showed that the reinforced composite samples have better enhancement in all the properties tested than the unreinforced control sample. Least Water Absorption (WA) value of 1.4 % were obtained within the 1 week and 2 week for the reinforced samples. Samples reinforced with 10 wt. % rattan fibres had the highest abrasion resistance, while the sample with 5 wt.% rattan fibre addition had the best water absorption resistance. The products of this research could find applications in automotive fields where exposure to moisture and wear are encountered.

Abrasion and Physical Properties of Rattan Cane (<i>Calamus deeratus</i>) Fibre Based Epoxy Composites

The effects of fibre content (5–30 wt%) and fibre treatment on abrasion, water absorption, specific gravity, and density properties of epoxy/rattan cane fibre composites were studied. Epoxy resin reinforced with the alkaline treated rattan cane fibre fibres was produced by compression technique in predetermined proportions. Abrasion and physical properties tests were carried out on the developed composites. The results showed that the reinforced composite samples have better enhancement in all the properties tested than the unreinforced control sample. Least Water Absorption (WA) value of 1.4 % were obtained within the 1 week and 2 week for the reinforced samples. Samples reinforced with 10 wt. % rattan fibres had the highest abrasion resistance, while the sample with 5 wt.% rattan fibre addition had the best water absorption resistance. The products of this research could find applications in automotive fields where exposure to moisture and wear are encountered.

Influence of designated properties on the characteristics of dombeya buettneri fiber/graphite hybrid reinforced polypropylene composites

This research presents the behavior of dombeya buettneri fiber/graphite hybrid composites which was studied to harness a favorable balance between the inherent advantages and disadvantages of natural and synthetic reinforcements. The fibers after extraction were chemically treated for surface modification. The composite was developed using compression molding process by randomly dispersing the reinforcements in the polypropylene matrix in predetermined proportions. The developed samples were tested to ascertain the response of the materials to the selected properties. Experimental results showed that hybrid composite sample C which is a blend of 12 wt% dombeya buettneri fiber (DBF) and 8 wt% graphite particle (GP) gave enhanced results in many of the properties which includes; hardness, impact, thermal insulation and abrasion resistance properties. Also, the hybrid composites sample denoted as sample E which is the blend of 6 wt% DBF and 14 wt% GP produce higher enhancement in the flexural properties and Young’s Modulus of Elasticity than other samples. Composite sample reinforced with dombeya buettneri fiber as single reinforced composites performed more in ultimate tensile strength compared to other samples while graphite particle reinforced sample emerges as the best in thermal conductivity. Diffusion of water into the composites also obeys Fick’s law where sample C was seen to be the best among the composites. It was therefore, discovered that the synergy between the two reinforcements has encouraged the improvement of polypropylene (PP) properties in a unique mode.

Mechanical and wear behaviour of pulverised poultry eggshell/sisal fiber hybrid reinforced epoxy composites

This study investigates the effects of calcined and uncalcined eggshell particles (ESP) and sisal fiber (SF) on the mechanical and wear properties of eggshell particles/sisal fiber reinforced epoxy composites. Egg shell was processed to obtain calcined and uncalcined egg shell particulate of −43 μm and sisal fibers was extracted by soil retting and treated with NaOH. The composite was developed using the hand lay-up method by blending the selected materials in predetermined proportions. SEM/EDS and XRD of the egg shell particles were carried out while mechanical and wear properties of the developed composites were evaluated. SEM images of the fracture surfaces were also examined. The results showed that eggshell particles contain CaCO3 and the uncalcined ESP/SF reinforced epoxy composite showed improved properties than the calcined ESP/SF composites in most of the tests performed. Also, it was observed that most of the tests gave the best results at different weight fractions. However, 3 wt. % emerged as the weight fraction with optimum values.