Good Quality Material Research Articles

The variability in commercial laboratory aggregate testing for road construction in South Africa

Simple data comparisons were undertaken using project data to illustrate the need for duplicate test analyses in road construction material investigations for hard rock aggregate sources. Test data was sourced from projects commissioned by the South African National Roads Agency SOC Limited (SANRAL). All test results except the polished stone value were reported by commercial geotechnical laboratories that are accredited with the South African National Accreditation System (SANAS). Only samples subjected to duplicate test analyses were used, as this method allows direct comparisons. The tests used for comparison included the polished stone value, wet and dry versions of the Aggregate Crushing Value test, wet and dry versions of the 10% Fines Aggregate Crushing Value test, the ethylene glycol-soaked version of the 10% Fines Aggregate Crushing Value test, and the water absorption test of both the fine (-5.00 mm) and coarse (+5.00 mm) material fractions. The results show that duplicate testing is firmly justified, as test results reported were often highly variable, despite all participating laboratories being SANAS-accredited and using standardised methods. Further consideration was then given to the additional cost of duplicate testing at project stage investigations compared to the cost implications of having erroneously reported materials failing in service or having good-quality materials rejected.

The procurement of quartz as a tool stone

The archaeological data suggest that the procurement of quartz was often times not a random or adventitious event, but rather an organized task of exploitation targeting geologic exposures which afforded good quality material in terms of composition, form, and quantity. In the absence of professionally collected data on quartz quarries or quartz extraction areas, an inferential approach can be substituted to afford some clarity to the issue. The study of patterning in recorded archaeological sites with dominant quartz tool stone assemblages can provide the means for identifying the geologic source areas and assist in precisely locating procurement areas.

The impact of fertilizers on the productivity of white mustard

Recently, scientists and producers have been paying increasing attention to niche crops that are able to significantly diversify the monocultural oil field of dominance in the crop rotation of sunflower, soybean and rapeseed. In today's climate, one of these crops is mustard, which at the same time, with the ability to form stable yields of seeds and raw materials of good quality, is distinguished by its relative unpretentiousness to external factors. Purpose. Improvement of elements of technology of cultivation and determination of their influence on productivity of mustard white. Methods. The studies involved the use of standardized methods: field – to determine the yield, biometric records and measurements, laboratory – to determine the agrophysical properties of the soil, the content of the basic nutrients in it, to determine the structure of the crop; calculated – evaluation of the economic efficiency of the elements of white mustard growing technology studied; statistical – analysis of variance. The article presents the results of studies to study the effect of different doses of fertilizers, micro fertilizers on seed yields and oil the content in white mustard seeds. Optimal parameters of elements of technology of cultivation of mustard white, which provide maximum yield in the conditions of the northern forest-steppe of Ukraine, are established. As a result of the research, it was found that the highest seed yield of white mustard seed (2,58 t/ha) with oil content (43,29 %) was provided by the application of fertilizer with fertilizer at a dose of N45P60K90 and foliar feeding with Tropicel. The significance of the influence of the investigated factors on the crop yield is estimated. It was established that in 2016–2018. factors in terms of the degree of influence on the yield of the white mustard variety Belaya Princess in terms of importance can be arranged as follows: mineral fertilizers – 14.3 %, treatment of crops with micronutrient fertilizer Tropikel – 52.2 %. Cost-effec-tiveness analysis showed that profitability (225 %) and profit (UAH 32158) reached the highest values by growing white mustard using technology that involves the introduction of N45P60K90 and foliar fertilization of Tropikel microfertilizers. Keywords: mustard white, mineral fertilizers, micro fertilizers, yield, seed quality, cost-effectiveness, Tropicel.

Analisis Kepuasan Pelayanan dan Faktor yang Mempengaruhi Keputusan Pelanggan untuk Memilih Smartphone Samsung di Jabodetabek Menggunakan Metode IPA dan Model Kano

Smartphones are one of the must-have devices for modern society today. With the high demand for smartphones lately, many companies are competing to produce smartphones that suit consumer needs. Indonesia is one of the developing countries where the growth rate of smartphone use can still increase so that many smartphone manufacturers sell their products to Indonesia. From this phenomenon, researchers want to know the level of satisfaction of users of one of the leading smartphone brands in Indonesia and even in the world, namely Samsung. The purpose of this study is to determine what factors are considered good by customers and the company must maintain these services and what things are deemed not good and need to be improved again. This study uses the IPA method to determine the level of conformity between company services and customer expectations and the Kano model used to determine which services are included in the performance, basic, or delighter categories. From the results of these two methods can be integrated using the IPA-Kano integration table. Some things that still need to be improved from Samsung smartphones according to users who have filled out this questionnaire include good quality materials at a good selling price, attractive and modern product designs, product quality has a good price level, sufficient camera quality for purposes daily needs, and bonuses that make consumers satisfied.

Mg acceptor doping in MOCVD (010) β -Ga2O3

In this Letter, in situ Mg doping in β-Ga2O3 was demonstrated via metalorganic chemical vapor deposition (MOCVD) epitaxy. The electrical insulating property of the Mg acceptors in β-Ga2O3 was found to be intrinsically activated in the as-grown Mg-doped β-Ga2O3 thin films. Growth conditions for MOCVD β-Ga2O3 were further explored and optimized at a lower growth temperature regime, leading to a better confinement of the Mg-doping profile. Detailed analysis of Mg diffusion characteristics revealed a diffusion barrier energy Ebarrier ∼ 0.9 eV for Mg in MOCVD β-Ga2O3, which is likely related to an interstitial-assisted process. Surface morphologies and electron transport were characterized on samples grown with different growth temperatures and Mg doping levels. The MOCVD growth method demonstrated its feasibility to grow semi-insulating Mg-doped β-Ga2O3 epilayers with controllable Mg incorporation while maintaining good material quality and smooth surface morphology. From capacitance-voltage charge profiling, it is verified that the Mg-doped buffer layer grown at the substrate-epilayer interface could effectively compensate the charge accumulation at the interface. The in situ acceptor doping of Mg in MOCVD β-Ga2O3 will provide versatility for designing β-Ga2O3 power devices.

Sustainable Construction of Earth Dams: Use of Heterogeneous Material from the Dam Site

The volumes of soil required for the construction of an earth dam are usually of importance, so that, consequently, a key aspect to mitigate the negative impacts of dam construction, both from an economic and environmental point of view, is the use of materials in the vicinity of the dam location. However, this is often complicated because the existence of good quality materials with homogeneous properties, necessary for the dam core, is scarce in sites near the dam and their presence in sufficient volume for its construction is not usual. Unfortunately, using and transporting soil with good geotechnical characteristics to construct the core in a faraway location is economically and environmentally unsustainable. Therefore, the possibility of using less suitable material at the dam site as part of the core must be studied. Thus, in the present research the use of a soil of great heterogeneity in its geotechnical properties with a great dispersion of permeability is analyzed. Considering permeability as a random variable, combinations of representative values of heterogeneous soils are analyzed using their mean permeability and coefficients of variation that allow generating different lognormal distribution functions to carry out a Monte Carlo analysis. By maintaining the soil’s global heterogeneity, it was possible to study an unlimited disposition of lifts of different permeability. The statistical formulation allowed the research of the variation of the seepage flows and maximum gradients produced as a function of the variability of their mean permeability, being able to detect the factors with the greatest influence on the generation of high flows and gradients. Thus, it was possible to verify how high gradients were obtained for situations in which the seepage flow rates were moderate and low; the highest maximum gradients were observed in the lowest lifts of the dam core. In addition, based on the results of the Monte Carlo analysis, design charts have been developed for flow rates and maximum gradients, dependent on the mean permeability and the coefficient of variation, which allow judging whether heterogeneous material can be used, under conditions of safety, for the construction of the core of a dam.

Comparison of growth structures for continuous-wave electrically pumped 1.55 μm quantum dash lasers grown on (001) Si

Semiconductor lasers directly grown on silicon offer great potential as critical components in high-volume, low-cost integrated silicon photonics circuits. Although InAs/InP quantum dash (QDash) lasers on native InP substrate emitting at 1.5 μm (C-band) have demonstrated notable performance, the growth of InAs/InP QDash lasers on silicon remains undeveloped because of the 8% lattice mismatch between InP and silicon. Here we report advances of growth techniques leading to the first C-band room-temperature continuous-wave electrically pumped QDash lasers on CMOS standard (001) silicon substrates by metalorganic chemical vapor deposition. A correlation between various material characterizations and device performance is analyzed for different QDash laser structures grown on planar nominal (001) silicon. With the optimized QDash growth and improved fabrication process, the lowest threshold current density of 1.5 kA / cm 2 was determined on an 8 μm × 1.5 mm device on planar silicon with a single facet output power exceeding 14 mW. The device results illustrate the good material quality of the QDash lasers grown on silicon, suggesting potential applications for other active components of photonic integrated circuits, such as semiconductor optical amplifiers, modulators, and photodetectors.

Identifying Carrier Behavior in Ultrathin Indirect-Bandgap CsPbX3 Nanocrystal Films for Use in UV/Visible-Blind High-Energy Detectors.

High-energy radiation detectors such as X-ray detectors with low light photoresponse characteristics are used for several applications including, space, medical, and military devices. Here, an indirect bandgap inorganic perovskite-based X-ray detector is reported. The indirect bandgap nature of perovskite materials is revealed through optical characterizations, time-resolved photoluminescence (TRPL), and theoretical simulations, demonstrating that the differences in temperature-dependent carrier lifetime related to CsPbX3 (X = Br, I) perovskite composition are due to the changes in the bandgap structure. TRPL, theoretical analyses, and X-ray radiation measurements reveal that the high response of the UV/visible-blind yellow-phase CsPbI3 under high-energy X-ray exposure is attributed to the nature of the indirect bandgap structure of CsPbX3 . The yellow-phase CsPbI3 -based X-ray detector achieves a relatively high sensitivity of 83.6 μCGyair-1 cm-2 (under 1.7 mGyair s-1 at an electron field of 0.17 V μm-1 used for medical diagnostics) although the active layer is based solely on an ultrathin (≈6.6μm) CsPbI3 nanocrystal film, exceeding the values obtained for commercial X-ray detectors, and further confirming good material quality. This CsPbX3 X-ray detector is sufficient for cost-effective device miniaturization based on a simple design.

Comparison of the existing and calculated blast design parameters for the rock mass conditions at Bamesso-Latet rock quarry

Blasting is the most cost effective methodology to break rock for mining engineering applications. A good production blast will break only the rock that is needed to be removed, leaving the host rock with minimal damage. Accurate measurement of blast, fragmentation is important in mining and quarrying operations, in monitoring and optimizing their design. Currently, there are several methods available to predict damage due to blasting. The accuracy of many of these methods is questionable, and in most cases, the methodologies over predict the results. This paper presents a practical method (i.e. Langefors’s method) that we shall use in Bamesso-Latet rock quarry to do a comparison between the existing and calculated blast design parameters. The proposed method allows to assess the rock damage from blasting. It shows great potential as a practical aid to control and get a good quality of the fragmented material in Bamesso-Latet rock quarry.

AUTOMATIC FISH GRILLER BASED ON TEMPERATURE CONTROLLER

The automatic fish grill is a tool that is very helpful for food vendors who are processed in a roasting manner. For now, conventional automatic grills that are already on the market have very expensive prices so that many traders still use manual fish grills which are less efficient in the process of doing them. The purpose of making this automatic fish grill design is to help human work to save more time and energy. The automatic fish roasting box is designed with heat absorbers in each layer, equipped with two racks, each measuring 50cm and also equipped with 2 250 watt heaters. From the test results using different types of carp with different weights, it shows that the automatic fish grill works well and gets a 100% percentage result with evenly cooked fish. The economical level of automatic fish grill has a good value, the whole design of automatic fish grill uses good quality materials and materials. For now, automatic roasters on the market have very expensive prices, this difference in price has made many traders not take full advantage of the technology. Because of this problem, researchers created an automatic fish grill based on a temperature controller, which is targeted at an inexpensive price, but can still be used safely and with maximum results. Thus, using a temperature controller-based automatic fish grill design can help simplify work to make it more efficient and safer.

Challenging Issues of Silicon Manufacturing Technology in Bangladesh

The knowledge related to available high-quality sand deposits, Si manufacturing process and different challenging issues in manufacturing is essential for developing the silicon industry in Bangladesh, which is addressed in this article. For high-tech applications, the primary element silica needs to be 98% pure, at least. A case study in Bangladesh shows that Bipinganj sand, with the high quartz percentages, low moisture content, is suitable for the industrial-grade silicon production. No trace of Boron content has been found in the sand of Shameshwari river near Bipinganj locality. Some other potential sand deposits in Bangladesh which contain a high amount of silica are Balijuri of Sherpur district, Moulvibazar, Dakshin zangal of Hathhazari Upazila in Chittagong district, Chauddagram of Comilla district and Shajibazar of Habiganj district etc. Metallurgical grade silicon (MG-Si) is the precursor for the solar grade (SoG) and electronic-grade silicon. In photovoltaic and electronic applications, an electric arc furnace is used for the growth of MGS. Some parameters, such as furnace temperature and heat loss, need to be considered for good quality material production. MG-Si can be produced through both carbon reduction and magnesium reduction processes. Mg reduction is comparatively expensive. Silicon production from waste glasses can be a potential technology for MG-Si production in respective to Bangladesh.

Preliminary results based on geochemical sedimentary constraints on the hydrocarbon potential and depositional environment of a Messinian sub-salt mixed siliciclastic-carbonate succession onshore Crete (Plouti section, eastern Mediterranean)

This study details new geochemical analysis from an outcrop in Crete to improve understanding of the hydrocarbon potential of the southern margin of the Hellenic Arc along the continental convergent zone of the central Mediterranean Ridge. Seventeen samples were collected from the Late Miocene sub-salt sedimentary succession of Plouti section in central Crete and were studied in terms of their organic geochemical features using Rock-Eval VI pyrolysis. Results of this investigation revealed intervals with sufficient organic material of good enough quality and quantity to be considered as potential source rocks. The obtained data generally present poor to fair and/or good in some cases hydrocarbon generation potential. The TOC values range from 0.03 to 1.99%, with an average fair (2.1 mg HC/g rock) hydrocarbon potential. A Type III kerogen was identified, indicating a terrestrial origin organic matter. T max and Production Index values suggest that the most promising parts of the section (organic-rich sediments) are immature with respect to oil generation and have not experienced high temperature during burial. Overall, the present study offers the opportunity to advance our understanding on the hydrocarbon potential onshore Crete and further investigate hydrocarbon prospectivity in the adjoining area, and particularly, the Greek part of the Mediterranean Ridge, a region with crucial economic and strategic importance.

Using Oil Palm Segregation Genetics to Decipher Illegitimate Seed Distribution Channels to Smallholder Farmers in Cameroon

Planting material or seed is the most determinant factor for oil palm productivity alongside agro climatological and management considerations. A study was conducted to determine the different varieties of oil palm planted in smallholders’ plantations, the distribution channels for oil palm seeds and all the actors involved in the seed trade sector in Cameroon. This is a bid to secure the supply of only improved planting materials to smallholder farmers. 230 oil palm smallholder plantations were surveyed and individual palms were subjected to varietal determination. The Chi-Square Test (c2) for Fixed Ratio Hypothesis (= 0.05) was used to determine whether the observed ratio deviates significantly from the Mendelian hypothesized genetic segregation ratio. Up to 65% of smallholder farms were found to be planted with poor planting material distributed in the different Mendelian ratios; 100% Dura, 50% Tenera and 50% Dura (1:1), 25% Dura, 50% Tenera and 25% Pisifera (1:2:1). The source of this poor quality planting material for these farms was deduced to come from private nursery entrepreneurs and workers of industrial plantations such as the Cameroon Development Corporation (CDC), Cameroon Palm Oil Company (SOCAPALM), Common Initiative Groups (CIG’s) and Non-Governmental Organisations (NGO’s). Farmers supplied by government services especially the Ministry of Agriculture and Rural Development and some of its specialized development projects all received good quality material. Thus, this is the only means now available which can assure the distribution of seeds good quality seeds

Research on monolithic AlGaInP/AlGaInAs/GaInAs/Ge quadruple-junction solar cell for high efficiency lattice-matched tandem photovoltaic device

Lattice-matched AlGaInP/AlGaInAs/GaInAs/GaInNAs(Sb)/Ge five-junction (5J) solar cell can be expected to achieve a practical efficiency high as 36% under the air mass (AM0) spectrum. In this work, AlGaInP/AlGaInAs/GaInAs/Ge quadruple-junction (4J) cells and relevant subcells are investigated as research foundation of Ge-based 5J device. An efficiency of 4J cell is obtained as 30.45% (AM0, 25 °C), with short-circuit current density (JSC), open-circuit voltage (VOC), and fill factor (FF) as 11.78 mA cm−2, 4.131 eV, and 85.5%, respectively. The JSC is close to the demand of 5J device with 36% efficiency, the high VOC and FF indicates a good material quality of 4J solar cell.

Production methods of ceramic-reinforced Al-Li matrix composites: A review

Recently, the increasing need for good quality, high performance, and low-cost materials has directed research to composite materials rather than monolithic materials. In the case of metal matrix composites (MMCs), composites based on aluminum matrix have been widely developed for the automobile and aerospace industry as well as structural applications due to having a low cost, high wear resistance, and high strength to weight ratio. Moreover, a facile and economical method for the production of the composites is a very important factor for expanding their application. Ceramic reinforcements such as graphite, silicon carbide, alumina, and fly ash particulates can be introduced in metal matrices. Moreover, there has been considerable interest in developing Al-Li alloys and composites because of having high specific strength and high specific modulus. The present article has focused on the development of aluminum-lithium alloy composites as well as their production methods.

Rock Material Recycling in Tunnel Engineering

In the construction industry, especially in tunneling or large-scale earthworks projects, huge quantities of excavation material are generated as a by-product. Although at first glance such material is undesirable, in many cases this material, if suitably treated and processed, can be recycled and reused on the construction site and does not necessarily need to be removed and deposited as waste at a landfill. In the simplest case, the material can be used as filling material with the least demanding requirements with regard to rock quality. Material of better quality often can be recycled as aggregate and be used as a substitute for conventional mineral aggregates. This approach generates numerous benefits regarding the costs for material procurement, storage and transport. In addition, reduction in environmental impact and demand for landfill volume can be achieved. The challenge lies in the fact that excavation material is not a standard aggregate in terms of geometric, physical and chemical characteristics and is subject to quality deviations during tunnel driving, mainly depending on the varying geology and applied excavation method. Therefore, preliminary research and experimental testing as well as specific evaluation and continuous examination of the rock quality during tunnel driving is necessary as well as ongoing adjustment of the rock processing plant to finally accomplish a high-quality level of recycled aggregates. This article illustrates the material investigations and treatment processes for the specific example of the Brenner Base Tunnel, the longest underground railway line in the world that is currently under construction. There, material recycling has already been successfully implemented.

СОВРЕМЕННЫЙ ПОДХОД К ПЕРЕОБРАБОТКЕ ДАННЫХ ПРОШЛЫХ ЛЕТ

This paper provides a brief description of the process and the results of reprocessing old seismic data of CDPP 2D, worked out in Soviet times and rewritten from old media immediately before reprocessing. Experience has shown that it is possible to obtain material of good quality, suitable not only for structural, but also for dynamic interpretation, with a more expressive reflection of the structure of deep horizons. Considerable efforts, including the cost of manual labor, required for such reprocessing, can pay off in the end with a good result.

Carbohydrates stimulated Amaryllidaceae alkaloids biosynthesis in Leucojum aestivum L. plants cultured in RITA® bioreactor.

BackgroundLeucojum aestivum L. is an important medicinal plant which produces Amaryllidaceae alkaloids, especially galanthamine and lycorine. Research is currently exploring the possibility of producing these alkaloids using biotechnological methods, including in vitro cultures. The biosynthesis of alkaloids may be affected by the types and concentrations of carbohydrate sources used in the medium. In the present investigation we performed such studies on in vitro cultures of L. aestivum with a view to obtaining plant material of good quality, characterized, in particular, by a high content of valuable Amaryllidaceae alkaloids.MethodsWe examined the effects of various types of carbohydrate sources—sucrose, glucose, fructose and maltose—at different concentrations (30, 60 and 90 g/L)—on the quality of L. aestivum plants grown in the RITA® bioreactor. The plants’ quality was assessed by their biomass increments, as well by as analysing photosynthetic pigments, endogenous sugar, phenolics and Amaryllidaceae alkaloid content. We also investigated the effect of sugars on the activity of the antioxidant enzymes catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD).ResultsThe highest biomass increments were observed in plants cultivated in the medium containing 90 g/L sucrose. The highest CAT activity was noted in cultures growing in the medium supplemented with 90 g/L maltose, while the highest POD activity was observed in the presence of 90 g/L fructose and 60 g/L maltose. No differences in SOD activity were observed. Moreover, the sugars did not affect the contents of chlorophyll a and carotenoids, whereas the highest amount of chlorophyll b was recorded in plants growing in the medium with 60 g/L maltose. No statistically significant differences were observed in the contents of endogenous sugars and phenolics in any in vitro conditions. However, the addition of sugar had a decisive effect on the biosynthesis of the Amaryllidaceae alkaloids. The highest distribution of alkaloids occurred in plants cultured in the medium containing 60 g/L sucrose. Six Amaryllidaceae alkaloids were detected in the plant tissue. The addition of 30 g/L fructose in the medium resulted in the accumulation of five alkaloids, including ismine, which was not identified in other analysed tissues. The highest concentration of galanthamine was observed in plants cultured in the presence of 30 g/L fructose and 60 g/L sucrose (39.2 and 37.5 µg/g of dry weight (DW), respectively). The plants grown in the medium containing 60 g/L sucrose exhibited the highest lycorine content (1048 µg/g of DW).ConclusionsThe type and concentration of sugar used in the medium have an essential influence on the biosynthesis of Amaryllidaceae alkaloids in L. aestivum plants cultured in a RITA® bioreactor. The results point to an interesting approach for commercial production of galanthamine and lycorine.

Stabilization of Expansive Soil Using Chemical Stabilizer with Cement

This Research work is aimed to evaluate the suitability of slightly alkaline liquid sodium silicate for stabilizationof black cotton soil of India. The study also aimed to investigate the effect of applying liquid sodium silicatewith ordinary Portland cement on engineering properties of treated soil. The Laboratory testing involved duringexperimentation are Atterberg limit test, Proctor test, California Bearing Ratio (CBR) test, Swelling test andUnconfined Compressive Strength (UCS) test. The locally available black cotton soil was treated on variouscombinations of liquid sodium silicate with ordinary Portland cement. The cement was taking 3 % constant andliquid sodium silicate varies 1%, 2%, 3%, 5% and 7% of dry weight of Soil. Samples were cured for 4,7,14 and28 days before testing. It was observed that(1) CBR and UCS values increases and reduced the swelling properties up to 3% combination.(2) Beyond 3% combination it reduces the strength development and increases the swelling properties.(3) Curing enhanced strength development from 4 to 28 days. [8]Findings of the Laboratory investigation imply that good quality materials, dense compaction, longer curing andproper proportion of stabilizer should be applied for Cementious stabilization. Only the liquid sodium silicate isnot a suitable stabilizer but it relatively gives encouraging results with combination of 3% cement by dry weightof soil. The Combination of 3% liquid sodium silicate with 3% cement by dry weight of soil was observed to bethe best combination for stabilization of expansive soil as black cotton soil.

Numerical child restraint system analysis in 6 years old infant during a dolly rollover test

This research analyzes the head and chest injuries with a finite element model of Hybrid III six years old during the vehicle rollover, using a passive safety Child restraint system (CRS). Vehicle seats and passive safety systems were modeled in CAD software. Subsequently, all elements were analyzed using the finite element method in the LS-DYNA® software. The border conditions were established for each study, in accordance with the Federal Motor Vehicle Safety Standard (FMVSS), following the FMVSS 213 standard for the mounting and fastening of the infant, the FMVSS 208 for the dolly rollover test methodology with which the vehicle rollover was performed. The vehicle Toyota Yaris 2010 was considered in all the analyzes. The numerical simulations were performed during an interval of 1 s, and there were obtained values every 2 ms to analyze the efficiency of the system and the restriction performance of the CRS system. It was compared the behavior when the chair uses a 5-point seatbelt, with respect to using the 3-point seatbelt, and what happens when holding the chair with the single seatbelt and with the ISOFIX anchorage. Three cases of studies were analyzed: Study I; CRS Study II; CRS with ISOFIX anchorage; and Study III; CRS with a seatbelt of 5-points. The outcome shows that the best restriction efficiency is that of the CRS 5 points seatbelt because it presents the lowest level of chest injury. In conclusion, the main factor to reduce injuries during a rollover accident is the correct anchoring of CRS, this is achieved with ISOFIX system, on the other hand, a good quality of material and a correct thickness used for the headrest could reduce the risk of a head injury.