Results Of Resistance Tests Research Articles

Predicting practical ship powering and speed loss in waves using added resistance test results

ABSTRACT This paper introduces a practical technique for accurately estimating ship propulsion and speed loss in the presence of waves. Utilising the previously established self-propulsion estimation framework, our approach enhances the method, which previously solely considered bare hull resistance, propeller performance, thrust deduction factor, and wake fraction, by incorporating added resistance test results. The full-scale DTC container ship is the focus of our investigation, providing a thorough examination of its performance in different sea states. The model's predictive abilities are enhanced by incorporating test data on added ship resistance, and it addresses a crucial aspect that is generally disregarded while estimating self-propulsion. This research is considered to be a contribution to the advancement of ship hydrodynamics, as it offers a practical and reliable tool for ship designers, operators, and researchers to accurately assess powering requirements and speed loss in harsh ocean conditions.

Study on the improvement of fatigue and crack resistance of semi-flexible pavement materials using the mixing -molding method

This study focuses on two significant issues pertaining to conventional grout-molded semi-flexible pavement material (P-SFP): the difficult of achieving a high grouting rate and the limited scope for enhancing asphalt content, both of which contribute to the poor crack resistance of the SFP. To address these problems, the Mixed-Molding Method Semi-Flexible Pavement Material (M-SFP) is proposed, which utilizes a combination of mixed-molding method to enhance the crack resistance and fatigue life of SFP. In order to investigate the effects of asphalt film thickness and gradation type, four different gradations and five different asphalt contents of M-SFP were designed based on the volume filling theory. The effects of asphalt film thickness and gradation type on the cracking resistance and fatigue life of M-SFP were investigated through various tests, including low-temperature bending, semi-circular bending tensile, and four-point bending fatigue test. The results were then compared with those of the control P-SFP. The test results show that the strain energy density of M-SFP is increased by 24.9 % and the fracture energy is increased by 52.1 % compared with the conventional P-SFP; the number of fatigue life times under 200με, 225με, and 250με microstrain are increased by 53.6 %, 41.3 %, and 47.3 %, respectively. Based on crack resistance test results, it is recommended that the design asphalt film thickness of M-SFP exceed 10μm. Furthermore, measurements of the air void content reveal that the M-SFP exhibits significantly better compactness compared to the P-SFP. In conclusion, it shows that the Mixing-Molding method can be used to obtain semiflexible pavement materials with higher asphalt dosage, better cracking resistance, better degree of compactness, and longer fatigue life. In addition, the correlation analysis between the cracking resistance results and the rigid-flex ratio indicates that the recommended design rigid-flex ratio for SFP should be less than 2.06.

Influence of Endodontic Cavity Design on Interfacial Voids, Class II Resin Composites Sealing Ability and Tooth Fracture Resistance: An In Vitro Study.

Objective: The aim of this in vitro investigation is to study the effect of endodontic cavity design on interfacial voids, class II resin composite sealing ability, and fracture resistance in mandibular premolars. Methods: A total of 48 single-rooted mandibular premolars received compound class II preparations with either traditional flare access cavities (group A) or contracted endodontic cavity preparations (group B). Each study group was subdivided according to the coronal restoration into two sub-groups as α and β. In the α group, a microhybrid composite was used after etch-and-rinse bonding technique using an MDP-containing universal adhesive. In the β group, a self-adhesive composite was used as coronal restoration after endodontic treatment (n = 12) for each subgroup. A micro-CT analysis was performed to assess the obturation interfacial voids and tracing of class II cervical interfacial adaptation. The tooth fracture resistance testing was then performed adding an extra group of 12 sound non-prepared teeth, which were tested as the control for fracture strength testing. A one-way ANOVA and post-hoc testing were used together with descriptive statistics for an analysis of the mean values of obturation interfacial voids. A two-way ANOVA was used to assess the fracture resistance test results, and to find the influence of endodontic access design and the type of composite material on the fracture resistance testing. Chi-square testing was employed to analyze the cervical interfacial seal of the class II restorations. Results: A one-way ANOVA revealed that there were no statistically significant differences between test groups in the amount of obturation interfacial voids (p > 0.05). There were no statistically significant differences between test groups in terms of cervical interfacial sealing ability (p > 0.05). A two-way ANOVA revealed that no statistically significant differences between test groups including the control group existed in terms of the fracture resistance testing (p > 0.05). Conclusions: Although it does not improve tooth fracture resistance, the contracted endodontic access cavity does not deteriorate the quality of obturation in terms of the interfacial porosity. The self-adhesive composite does not improve the efficiency of cervical interfacial adaptation or tooth fracture resistance regardless of the endodontic access cavity shape, yet it revealed a substantial load-bearing capacity.

Isolation of Lactobacillus spp. from Healthy Infants' Feces and Study of their Antibiotic Susceptibility

This study aimed to isolate Lactobacillus spp. bacteria from the feces of healthy newborns and investigate their susceptibility to antibiotic resistance. 120 fecal samples were obtained from infants under 12 months of age and susceptibility was identified using biochemical tests and molecular identification methods. A total of 30 positive isolates, chosen randomly from the 90 positive samples, were selected to conduct a safety assessment. the isolates were analyzed for their hemolytic activity and susceptibility to antibiotics. Using 16S rRNA sequencing, a total of 30 positive isolates were determined to be lactobacillus spp. The results of the antibiotic resistance test indicated that the majority of the isolates showed susceptibility to tetracycline, chloramphenicol, gentamicin, clindamycin, and amoxicillin while demonstrating resistance to vancomycin, nalidixic acid, streptomycin, and amikacin. conclusion: Based on these specific traits, the isolates of Lactobacillus spp. demonstrated favorable qualities as probiotics.

Characterization method of conductive film state of micro-cathode arc thrusters

Micro-Cathode Arc Thruster (μCAT) is an advanced electric propulsion system developed in the past decades to meet the maneuvering requirements of space microsatellites. However, the constraint on the its application is the short lifespan of the thruster. This is attributed to the conductive film, a key component of thruster discharge. In this study, we propose a measurement method for μCAT conductive film, and enables the evaluation of the evolution process of film thickness. The method is based on the four-probe resistivity testing theory and size effect fitting model, and establishes a method for characterizing the thickness and resistivity of μCAT conductive films. A comparison was made between the corrected resistivity test results of 1, 2, 5, and 10 μm film and the fitting results of the titanium film, revealing an error ofapproximately 10%. Additionally, a total of 2500 ignition experiments were conducted to verify the film thickness and resistance measurement of this method. This research serves as a valuable basis for the lifetime investigation of μCAT. Consequently, the thickness of the film progressively decreases with each discharge cycle, and the resistivity exhibits a corresponding increase due to the size effect. This method could be used as an effective method for exploring the μCAT lifespan and performance.

The Impact of Natural Fibers on Thermal Resistance and Spalling in High-performance Concrete

This article presents an experimental approach to evaluate the effectiveness of palm fibers as a natural innovative solution to enhance the thermal resistance of high-performance concrete (HPC) under fire conditions. The utilization of palm fibers aims to promote local materials, since locally sourced materials may be more affordable due to their abundance. Four different high-performance concrete formulations were tested. The first, called HPCSF, which is composed of fibreless silica fumes, served as a reference mix. The second, HPCPSF, included the addition of polypropylene fibers to silica fume. The third, HPCDFSF, integrates date palm fibers with silica fume. Finally, the fourth, HPCPQSSF, combined polypropylene fibers with varying amounts of quarry sand and silica sand, in addition to silica fume. The results of the fire resistance tests show that the incorporation of palm fibers into the concrete mixture improves structural strength, reduces spalling, prevents crack formation under high-temperature conditions, and increases fire resistance in HPC.

The epidemiological characteristics of the outbreak of Dengue fever in Fuzhou City from 2016 to 2023

To analyze the epidemiological characteristics of dengue fever in Fuzhou City from 2016 to 2023, it was found that a total of 1 697 cases of Dengue fever (1 512 local cases and 185 imported cases) were reported in Fuzhou City from 2016 to 2023, and a total of 15 dengue-related public health emergencies were reported, with an average duration of the epidemic. The average duration of the epidemic was 71.6 days. Local dengue fever cases: the peak incidence period was concentrated in August-October, accounting for 96.69% (1 462/1 512); distributed in 10 counties and districts, the three counties with the highest annual average incidence rate were Minhou County (9.95/100 000), Cangshan District (6.03/100 000), and Taijiang District (5.58/100 000); in 2019 (Moran's I=0.18, P<0.05) and 2023 (Moran's I=0.5, P<0.05) the spatial distribution of local dengue fever cases in Fuzhou City showed a clustering pattern, with Gulou, Taijiang, Cangshan, and Jin'an districts as high-high clustering areas, and the outbreaks basically clustered in the urban areas; the median age was 47 years old, and the proportion of 40-70 years old was 50.93% (770/1 512). Among the local cases of Dengue fever, 81.15% (1 227/1 512) were unemployed, and 6.81% (103/1 512) were students with the highest proportion.The median time between onset diagnosis was 3.38 d, 6.67 d, 3.50 d, 3.75 d in 2016-2019, and 3.46 d in 2023, respectively, and the years of onset. The difference in the median time between onset and diagnosis was not statistically significant (χ²=8.556 4, P>0.05). Imported cases: mainly from Southeast Asian countries, Cambodia, Papua New Guinea, Indonesia accounted for the highest proportion of 62.70% (116/185); May to September is the active period of Aedes albopictus, and the results of Aedes albopictus resistance test showed that the mosquito larvae were sensitive to residual chlorpyrifos, and the Aedes albopictus adult mosquitoes showed sensitivity to two organophosphorus insecticides (chlorpyrifos, malathion), and to one type of Aedes albopictus adults were sensitive to two kinds of organophosphorus insecticides (chlorpyrifos, malathion) and a kind of pyrethroid carbamate insecticide (carbofuran).

The Usefulness of Soil Penetration Resistance Measurements for Improving the Efficiency of Cultivation Technologies

The research results of soil penetration resistance (SPR) tests carried out on sandy clay using four cone probes with different dimensions of the measuring tip are presented in this study. It was indicated that the values of SPR can be used to diagnose the cultivation layer and, on this basis, determine whether it is necessary to cultivate it and select tools for the required treatment. Tests were carried out on three levels of soil density, 1.37, 1.43 and 1.51 g∙cm−3, and two moisture contents, 7.64% and 10.4%. The results show that the probe with the smallest cone with apex angles of 30° and 60° on the least dense soil indicated higher SPR by over 50% more than other probes with the highest cone and the same opening angles. The change in cone opening angle from 30° to 60° led to an increase in probe indications in the range of 10–25%, depending on the diameter of the cone tip. The statistical analysis shows that values of probe indications were statistically significant and were influenced by soil density, probe cone tip dimensions, the surface of the base and the apex angle. The values of SPR are fundamental in diagnosing the quality of the soil’s top layer, determining the necessity of breaking it up, and selecting the optimal tools for this procedure. To improve the efficiency of agricultural crop cultivation technologies. This is particularly important when carrying out cultivation procedures in an environmentally friendly manner. The measurements will help support the introduction of sustainable farming practices, including direct seeding, no-till cultivation, or precision agriculture, reducing soil degradation and increasing environmental benefits.

Utilization of spent bleaching earth as green filler and plasticizer in the manufacture of rubber compounds for solid tire production

This study utilized spent bleaching earth (SBE) as a single form of filler and plasticizer in the manufacture of rubber components for solid tire vulcanizate. SBE, an underutilized byproduct of vegetable oil purification, is abundantly available globally and can be used as a filler and plasticizer in rubber compounds. This aligns with environmental sustainability principles, reduces disposal costs, and lowers raw material expenses in rubber manufacturing. In this research, the SBE was applied for each formula from SBE-02 to SBE-05 at ratios of 15–30 per hundred rubber (phr). As a comparison, carbon black (CB) filler (65 phr), CaCO3 (35 phr), and plasticizer derived from petroleum in the form of paraffinic oil (PO) (6 phr) were used. Rubber components were produced by masticating natural and synthetic rubber in an open mill, followed by the addition of filler, plasticizer, accelerator, co-activator, anti-degradant, and vulcanization agent. The resulting compounds were vulcanized at 150 °C and 10 MPa for 17 minutes. The test results demonstrated that incorporating SBE at a ratio of 15 phr (SBE-02) significantly reduced the cure time (t90) to 8 minutes and 20 seconds, the shortest among all tested formulations. The mechanical properties of the SBE-02 vulcanizate rubber met the requirements for solid wheelchair tire applications, with a hardness of 70 Shore A. However, its abrasion resistance test result of 189.1 g/cm³ was the lowest among the formulations tested. Furthermore, the scorch time (ts2) of the SBE-02 was determined to be 2 minutes and 35 seconds. Results from a 1000x magnification scanning electron microscope (SEM) reveal air gaps on all sample surfaces of different sizes. The elements C, O, Zn, Si, Ca, and Pb dominate the SEM-EDX results for all rubber vulcanizate samples from all three spectra, in varying weight percentages. The identification of functional groups with FTIR on all rubber vulcanizate samples shows Si–O–Si bending at 2, 4, and 5 and Si–O–Al stretching at 3, 5 on the wave number spectrum of 680–413 cm−1 Si–O–Si on the wave number spectrum 1100–1050 cm−1 from the infrared spectrum.

Prevalence And Pattern Sensitivity Multidrug Antibiotics Resistant Pseudomonas aeruginosa in the High Care Unit at Dr. Soetomo General Academic Hospital Period 2022-2023

The prevalence of Multidrug antibiotic-resistant Pseudomonas aeruginosa (MDRPA) has been increasing during the decade And has become attention in hospital patients. This retrospective descriptive descriptive aimed to determine the prevalence of MDRPA and its sensitivity patterns. Data were taken from results of bacterial culture and antibiotic resistance tests from various clinical specimens from patients at Dr. Soetomo General Academic Hospital throughout 2022-2023. The resistance test was carried out using a Vitek 2 compact instrument. MDRPA is defined as Pseudomonas aeruginosa that is not sensitive to three or more of the following classes of antibiotics: meropenem or imipenem, ciprofloxacin, gentamicin or amikacin, ceftazidime or cefepime, and piperacillin/ tazobactam. The prevalence of MDRPA was 57.0%. MDRPA isolates were also the most common origin from the burn unit and HCU A (high care unit A), mostly from pus specimens and sputum. Pseudomonas aeruginosa sensitivity was best with piperacillin/tazobactam (55.5%), meropenem (54.8%), amikacin (47.5%), gentamicin (46.5%), cefepime (46.3%), ceftazidime (45.0%), ciprofloxacin (44.7%) and aztreonam (43.2%). The sensitivity of MDRPA to antibiotics is much lower than that of Pseudomonas aeruginosa. This study showed high number of MDRPA specifically in Surabaya and the pattern sensitivity of Pseudomonas aeruginosa can become guidelines in choosing antibiotics treatment for patients.

СРЕДСТВА ПОЛУЧЕНИЯ И ПЕРСПЕКТИВЫ ПРИМЕНЕНИЯ КОМПРЕССИОННОЙ ПЕНЫ В ПОЖАРОТУШЕНИИ

The subject of the article is modern fire extinguishing technologies based on compression foam. The purpose of the study is to study the means of obtaining and the prospects for using compression foam in fire fighting. Methods: analysis and synthesis, modeling. The results obtained indicate that compression foam has a number of advantages compared to water and conventional air-aspirated foam, so it can be used to extinguish fires in many industries and areas. A diagram of the production of compression foam is presented (the foam concentrate acts as a foaming agent) and a diagram of an autonomous installation for the production of compression foam. It is noted that one of the significant advantages of CAFS is the ability to create a finished product that matches a specific type of fuel or a specific situation. The characteristics of the SmartCAFS product have been defined. A typology of the use of compression foam depending on the type of incident is presented. The results of fire resistance tests of various foams are presented. It is concluded that fire suppression systems using compression foam have significant advantages, such as minimizing the spread of fire, the volume of water required to cover large areas, costs and placement, and the integration of CAFS with digital technologies.

Analysis of Tribological Properties of Hardfaced High-Chromium Layers Subjected to Wear in Abrasive Soil Mass.

This article presents the results of abrasion wear resistance tests of wear-resistant steel and surfacing under laboratory conditions and natural operation. Abrasion wear resistance determined on the basis of the study by determining geometrical characteristics of the alloying additives using computer image analysis methods, as well as examining the changes occurring on the surface of the workpieces and their wear intensity. Based on the results obtained from laboratory tests, it was noted that AR steel exhibited 14 times greater wear than the padding weld. This wear is affected by alloy additives, which, for the padding weld, are chromium additives. The microstructure image shows that soil mass had a destructive effect mainly on the matrix of the material, whereas in the areas with high concentrations of chromium precipitates, this effect was significantly weaker. The operational test results showed that within the area of the tine subjected to hardfacing, the material loss was lower than that for the same area of the tine in the as-delivered state. For the hardfaced tine, a 7% loss of volume was noted in relation to the operating part before testing and following the friction process. However, for the operating part in the as-delivered state, this difference amounted to 12%.

Four-quadrant propeller hydrodynamic performance mapping for improving ship motion predictions

On the path toward fully autonomous sea vessels, forecasting a ship’s exact velocity and position during its route plays a crucial role in dynamic positioning, target tracking, and autopilot operations of the unmanned body navigating toward predetermined locations. This paper addresses the prediction of the operational performance of a free-running submarine advancing in a straight route (in surge motion). Along with the forward advancing vessel (straight-ahead motion) the study covers all possible scenarios of ship’s surge, including crash-ahead, crash-back, and astern motions. Conventional maneuvering models cannot handle motions other than forward advancement due to the absence of propeller data in all four quadrants of hydrodynamic performance map. This study proposes an approach for predicting submarine performance in all these surge conditions by utilizing four-quadrant propeller performance and resistance test data. We developed an in-house code, SMot4QP, to simulate ship speed and position in the time domain. We obtained satisfying results for the straight-ahead and crash-ahead motions, while the crash-back and astern maneuvers require further refinement due to propeller wake interaction with the hull. The proposed method is capable of predicting the motions of all types of vessels using the ship’s resistance and four-quadrant propeller test results. Thus, SMot4QP offers a fast and robust alternative to computationally expensive free-running self-propulsion simulations for operational performance prediction in broader naval applications.

Management of Severe Odontogenic Infection: Case Report

Introduction: Submandibular abscess caused by odontogenic infection is a frequent case, but in some cases it can be deadly because it spreads and blocks the respiratory tract. The purpose of this study is to described a case of fatal submandibular abscess with early management effective. Case report: A 46 years old male patient with complaints of left submandibular, submental, left buccal and left temporal swelling. History of systemic disease was denied. Patients complain of tightness and changes in voice. Therapeutic intervention consists of Covid- 19 screening, complete blood lab, abscess decompression under local anesthesia, left submandibular and submental through and through drainage incisions, drainage incisions in the buccal area as well as multiple tooth extractions and penrose drain applications both extra oral and intra oral carried out in general narcotics, and swab culture sensitivity and antibacterial resistance tests were carried out. The antibiotics given were ceftriaxone and metronidazole. The patient was followed up and showed good general condition and decreased swelling. Conclusion: Odontogenic infections that spread and block the respiratory tract can be deadly. The abscess can expand even more quickly during preparation for surgery. Decompression of an abscess can be an effective treatment so that the abscess does not spread further and can reduce the risks of the operation being carried out. The management carried out must be complete and comprehensive, in this case a drainage incision and extraction of the focal infection are carried out. Initially, broad spectrum antibiotics can be given, but if the results of the antibacterial resistance test are obtained, it is very important to give more specific antibiotics. Submandibular abscess with poor prognostic consequences obstructed respiratory tract must be treated immediately and closely monitored. Keywords: Abscess, Odontogenic infection, Decompression

ИССЛЕДОВАНИЕ ВЛИЯНИЯ СОСТАВА КОМПОЗИТОВ, СОДЕРЖАЩИХ ИМПАКТНЫЕ АЛМАЗЫ, НА ИХ ЭКСПЛУАТАЦИОННЫЕ ХАРАКТЕРИСТИКИ ПРИ ЛЕЗВИЙНОЙ ОБРАБОТКЕ ЦВЕТНЫХ МЕТАЛЛОВ

The paper presents the results of resistance tests of tool composite materials containing nanostructured impact diamonds, in comparison with composites based on synthetic superhard materials, diamond and cubic boron nitride (cBN), and ВК-8 (VK-8) (WC + 8 % Co) hard alloy, during blade processing of workpieces made of brass ЛС-59 (LS -59) (57–60 % Cu) and aluminum alloy AK-7 (Al 92–94 %, Si 6–8 %). Samples of composite materials for wear resistance studies were obtained by thermobaric sintering in a highpressure apparatus. The performance of composites was assessed by the wear of the cutter back surface, as well as by a specially developed method for studying the performance characteristics of composite superhard materials, based on determining their specific productivity. As a result of the tests, it is found that composites based on impact diamonds have the highest resistance when turning non-ferrous metal alloys. In particular, the wear resistance of a composite material containing impact diamonds with the addition of cBN exceeds the wear resistance of cutters made of composite 02 (belbor) by 1.5–3 times, and that of cutters made of hard alloy VK-8 by 8–10 times. Additions of impact diamond to hard alloy in the amount of 6.25 and 12.5 vol.% increase the relative wear resistance of the hard alloy composite compared to the original VK-8 alloy by 10–15 and 20–25 %, respectively.

Investigating lactic acid bacteria genus Lactococcus lactis properties: Antioxidant activity, antibiotic resistance, and antibacterial activity against multidrug-resistant bacteria Staphylococcus aureus

BackgroundLactic acid bacteria (LAB) are utilized as a starter culture in the manufacturing of fermented dairy items, as a preservative for various food products, and as a probiotic. In our country, some research has been carried out, even if LAB plays a principal role in food preservation and improves the texture and taste of fermented foods, that is why we tried to evaluate their probiotic effect. The objective of this research was to determine the antibacterial activity of Lactococcus lactis (L. lactis) against Staphylococcus aureus (S. aureus) ATCC 29213, investigate their antioxidant activity, and characterize their sensitivity against 18 antibiotics. MethodsA total of 23 LAB (L. lactis subsp. cremoris, L. lactis subsp. Lactis diacetylactis, L. lactis subsp. lactis) were isolated from cow's raw milk. The antibacterial activity was performed using two techniques, competition for nutrients and a technique utilizing components nature, using the disk diffusion method. The sensitivity of the studied LAB to different antibiotics was tested on Man rogosa sharp (MRS) agar using commercial antibiotic disks. All strains of LAB were examined for their antioxidant activity. The antioxidant activity of L. lactis was tested by 2,2-diphenyl-1 picrylhydrazyl (DPPH). ResultsThe results showed that the MRS medium was more adapted than Muller Hinton Agar (MHA) to investigate the antibacterial activity of L. lactis against S. aureus ATCC 29213. Also, L. lactis exhibited a notable degree of antibacterial activity against S. aureus ATCC 29213. L. Lactis subsp. Lactis displayed higher antibacterial activities, followed by L. lactis ssp. lactis biovar. diacetylactis, and lastly, L. lactis ssp. cremoris against S. aureus ATCC 29213. Lc 26 among all strains of L. lactis showed a high potential antibacterial activity reaching 40 ± 3 mm against S. aureus ATCC 29213. All strains of L. lactis showed a slightly moderate antioxidant activity (10.56 ± 1.28%-26.29 ± 0.05 %). The results of the antibiotic resistance test indicate that all strains of L. lactis were resistant to cefotaxime, sulfamethoxazole-trimethoprim, and streptomycin and were sensitive to Ampicillin, Amoxicillin, Penicillin G, Teicoplanin, Vancomycin, Gentamicin 500, Tetracycline, and Chloramphenicol. These test results indicate that this strain falls within the criteria of not posing any harmful effects on human health. The important antibacterial properties recorded for all L. Lactis strains were derived from the production of antibacterial active metabolites, such as protein, diacetyl, hydrogen peroxide, and lactic acid, together with the fight for nutrients. ConclusionThis study suggests that the strains of L. lactis could be added as an antibacterial agent against S. aureus ATCC 29213 and can provide an important nutritional property for their antioxidant potential.

The mechanical and frost resistance properties of pressed concrete blocks mixed with the polymeric aluminum chloride waste residue.

This study aims to research on the mechanical and frost resistance properties of pressed concrete blocks mixed with the polymeric aluminum chloride (PAC) waste residue. Experimental studies on the activity index of volcanic ash, mechanical property, frost resistance and microstructure of pressed concrete blocks mixed with PAC waste residue were carried out. The results show that the activity index of volcanic ash of PAC waste residue reaches 74.96% at a particle size of 0.075mm or less and a curing age of 28days. Based on results of mechanical property tests, the optimum dosage of PAC waste residue is 15%, at which time the compressive and bending strength only decreases by 14.57% and 15.84%. Based on results of frost resistance tests, the optimum dosage of PAC waste residue for pressed concrete blocks is 10%. After 50 freeze-thaw cycles, when the dosage of PAC waste residue is 10%, the strength loss rate is only 3.04%. XRD and SEM tests show that PAC waste residue participates in chemical reactions. With a small amount of PAC waste residue, the structure of the specimen remains dense and therefore the strength decreases less.

Exploring the relationship between the supination resistance test and the effects of foot orthoses on the foot and ankle biomechanics during walking

BackgroundThe effects of foot orthoses on lower limb biomechanics during walking have been studied extensively. However, the lack of knowledge regarding the effects of various foot orthoses models for the same population complicates model selection in clinical practice and research. Additionally, there is a critical need to enhance our ability to predict the outcomes of foot orthoses using clinical tests, such as the supination resistance test. Research questionWhat are the effects of two commonly prescribed types of FO (thin-flexible and medially wedged) on lower limb biomechanics during gait? Is there a correlation on these effects with the results of the supination resistance test? MethodsTwenty-three participants with flat feet were enrolled in this cross-sectional descriptive study. Participants underwent walking trials under three conditions: shod, thin-flexible FOs and medially wedged FOs. Midfoot, ankle, knee and hip angles, moments were calculated. Repeated measure ANOVAs were employed for within-group comparison across conditions. Correlations between the effects of FOs on foot and ankle angles/moments and supination resistance were determined using regression analyses using a statistical parametric mapping approach. ResultsThin-flexible and medially wedged FOs reduced midfoot dorsiflexion angles and ankle inversion moments. Medially wedged FOs also decreased midfoot and ankle abduction angles, midfoot plantarflexion moments compared to thin-flexible FOs and shoes. Moderate to good correlations between the supination resistance test and the medially wedged FOs were observed for the frontal and transverse ankle angles and moments. SignificanceMedially wedged FOs are more effective in modifying lower limb biomechanics during walking compared to thin-flexible FOs. Greater supination resistance was associated with more pronounced effects for medially wedged FOs on foot and ankle biomechanics. These findings hold promise for refining orthotic prescription strategies, potentially offering advantages to individuals with musculoskeletal disorders.

Comparison of Tire Rolling Resistance Measuring Methods for Different Surfaces

The rolling resistance of car tires is one of the most important parameters characterizing tires today. This resistance has a very significant contribution to the energy consumption of wheeled vehicles. The climate crisis has forced tire and car manufacturers to place great emphasis on the environmental impact of their products. Paradoxically, the development of electric vehicles has led to an even greater importance of rolling resistance, because in electric vehicles, a large part of the influence of grade resistance and inertial resistance has been eliminated due to re-generative braking, which resulted in rolling resistance and air resistance remain as the most important factors. What is more, electric and hybrid vehicles are usually heavier, so the rolling resistance is increased accordingly. To optimize tires for rolling resistance, representative test methods must exist. Unfortunately, the current standards for measuring rolling resistance assume that tests are carried out in conditions that are far from real road conditions. This article compares the results of rolling resistance tests conducted in road conditions with the results of laboratory tests conducted on roadwheel facilities. The overview of results shows that the results of tests conducted in accordance with ISO and SAE standards on steel drums are very poorly correlated with more objective results of road tests. Significant differences occur both in the Coefficients of Rolling Resistance (CRR) and in the tire ranking. Only covering the drums with replicas of road surfaces leads to a significant improvement in the results obtained. For investigations of rolling resistance in non-steady-state conditions, the flat track testing machine (TTF), equipped with asphalt cassettes, is shown to provide measurement data in agreement with the road test data.

Production of a sustainable cement through the usage of clay as binding element

The formulation of a calcined clay-based hydraulic binder is an innovative solution for reducing the carbon footprint in the construction industry. This binder is made from calcined clay, a natural and abundant material that does not require high-temperature firing in the 400C to 950C range. In our study, we worked respectively under the following temperatures: 550C, 650C, 750C and 850C, unlike traditional binders whose clinker is fired at a temperature of around 1450C. The blaine tests showed that the binder had been well ground, resulting in a much finer binder. We then obtained various blaines varying between 5000 and 8000 Cm2/g, unlike the blaine of the traditional binder, which is 3800 Cm2/g; the residue rate is very high compared with that of the traditional binder, due to the grinding carried out in a laboratory ball mill. The results of resistance tests at 30% gave 34.8, 48.8, 36.5 and 46 respectively; those at 40% gave 42.7, 45.4, 44.4 and 44.8, while the resistance of traditional binder gave 42.5. In other words, we obtained strengths comparable to those of the traditional binder. In addition, it was found that the manufacture of calcined clay-based hydraulic binders reduces CO2 emissions compared with traditional binders, which emit very high levels of CO2, making the production of calcined clay-based binders a more environmentally-friendly option for the cement industry. The financial assessment carried out at the end of this study shows that the production of a calcined clay-based binder is more economical than that of a traditional binder (Portland cement).