Test Method For Resistance Research Articles

Experimental Study on Fire Resistance of Building Steel Structure Fireproofing Material

The definition and connotation of the steel structure fire protection material are briefly given, and the relationship between the fire resistance and the HP/A is analyzed and summarized according to the domestic refractory test data of the typical laboratory exposed steel structure. According to the existing specification, the necessity of fireproof protection, the application and basic requirements of the steel structure fire protection material and the necessity of adopting the steel structure fire protection material are put forward, pointing out the existing problems of fire protection technology, exploring other fire protection materials. Reasonable proposal have been given for the fire resistance test standard system, the relevant standards and norms of the system: Develop different fire resistance test methods should be made for different fire situations, and the corresponding assessment methods should be made for practical engineering application. And then the further content that needs to be studied in this field has been pointed out. Although there are many deficiencies that the steel structure fire protection materials transfers from the development, product characteristics, test methods or standard systems and test data to the actual application of the transition, but the actual demand decisions the broad prospects of this area, so it is of great significance to carry out its fire performance test.

Multimethod Longitudinal HIV Drug Resistance Analysis in Antiretroviral-Therapy-Naive Patients.

The global intensification of antiretroviral therapy (ART) can lead to increased rates of HIV drug resistance (HIVDR) mutations in treated and also in ART-naive patients. ART-naive HIV-1-infected patients from Cameroon were subjected to a multimethod HIVDR analysis using amplification-refractory mutation system (ARMS)-PCR, Sanger sequencing, and longitudinal next-generation sequencing (NGS) to determine their profiles for the mutations K103N, Y181C, K65R, M184V, and T215F/Y. We processed 66 ART-naive HIV-1-positive patients with highly diverse subtypes that underlined the predominance of CRF02_AG and the increasing rate of F2 and other recombinant forms in Cameroon. We compared three resistance testing methods for 5 major mutation sites. Using Sanger sequencing, the overall prevalence of HIVDR mutations was 7.6% (5/66) and included all studied mutations except K65R. Comparing ARMS-PCR with Sanger sequencing as a reference, we obtained a sensitivity of 100% (5/5) and a specificity of 95% (58/61), caused by three false-positive calls with ARMS-PCR. For 32/66 samples, we obtained NGS data and we observed two additional mismatches made up of minority variants (7% and 18%) that might not be clinically relevant. Longitudinal NGS analyses revealed changes in HIVDR mutations in all five positive subjects that could not be attributed to treatment. In one of these cases, superinfection led to the temporary masking of a resistant virus. HIVDR mutations can be sensitively detected by ARMS-PCR and sequencing methods with comparable performances. Longitudinal changes in HIVDR mutations have to be considered even in the absence of treatment.

Testing of the Oxidation Resistance of MgAlON Materials with Non-isothermal Oxidation Method

In order to establish a standardized testing method for the oxidation resistance of refractory materials, one of their most important properties, China national standard GB/T 32329-2015 has been issued in 2015, which title is “Test method for oxidation resistance of oxynitride materials—non-isothermal oxidation”. GB/T 32329-2015 provides a standard characterizing method for oxidation resistance. In this paper we validate this standard through testing the oxidation resistance of six MgAlON samples with the non-isothermal oxidation method described in this standard. We conclude that the oxidation resistance property of MgAlON materials could be well described with these indicators: the oxidation weight gain per unit area, the initial oxidation temperatures and the maximum oxidation rate temperatures. Our experiments show that this method is scientific and feasible.

Designing and Implementation a Lab Testing Method for Power Cables Insulation Resistance According with STAS 10411-89, SR EN ISO/CEI/17025/2005

Insulation resistance measurement is one of the most important tests required by standards and regulations in terms of electrical safety. Why these tests are is to prevent possible accidents caused by electric shock, damage to equipment or outbreak of fire in normal operating conditions of electrical cables. The insulation resistance experiment refers to the testing of electrical cable insulation, which has a measured resistance that must be below the imposed regulations. Using a microcontroller system data regarding the insulation resistance of the power cables is acquired and with SCADA software the test results are displayed.

Flame-Retardant Pressure-Sensitive Adhesives Derived from Epoxidized Soybean Oil and Phosphorus-Containing Dicarboxylic Acids

In this study, novel biobased pressure-sensitive adhesives (PSAs) derived from epoxidized soybean oils and carboxylic acid-terminated polyesters were developed with flame retardance, thermal stability, and peel strength comparable to those of current PSAs. The dynamic mechanical analysis indicated that the PSAs exhibited a dynamic mechanical response consistent with related high-performance PSAs. The thermal properties of the PSAs were investigated by thermogravimetric analysis, and the results suggested that the onset decomposition temperatures in both nitrogen and air atmospheres were improved by incorporating both 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-10-phosphaphenanthrene-10-oxide (DDP) and 2-(6-oxido-6H-dibenz oxaphosphorin-6-yl)-1,4-hydroxyethoxyphenylene (DOPO-HQ-HE) as the flame-retardant monomer. Microscale combustion calorimetry, the limiting oxygen index test, UL-94, and the test method for flame resistance of PSA tapes were used to evaluate the flame retardance of the PSAs....

Laboratory test method for dirt pickup resistance and stain removal

The pollution characteristics of current atmospheric particulates was summarized in the present investigation. The composition and proportion of the pollution sources used for dirt pickup resistance and stain removal test were adjusted, and the pollution sources used for new type dirt pickup resistance and stain removal test produced. In addition, a new dirt pickup method was adopted, and a set of new type laboratory dirt pickup resistance and stain removal tests developed by taking comprehensive consideration of the existing state and dirt pickup mode of actual atmospheric particulates. It verifies the rationality, feasibility and effectiveness of new test methods for dirt pickup resistance and stain removal based on the contrast test over the new and old test methods.

Criteria for Freeze-Thaw Resistant Concrete Mixtures

Abstract Concrete, especially for improved durability, is typically specified with prescriptive provisions. More recently there has been increasing interest in evolving towards performance-based specifications, both within state highway agencies and industry (FHWA, 2014, “Guide to Developing Performance-Related Specifications, FHWA-RD-98-155, FHWA-RD-98-156, FHWA-RD-98-171, Vol. III, Appendix C,” http://www.fhwa.dot.gov/publications/research/infrastructure/pavements/pccp/pavespec/, last accessed July 28, 2014; ACI Committee 329, Report on Performance-Based Requirements for Concrete, American Concrete Institute, Farmington Hills, 2010; The P2P Initiative, 2014, “National Ready Mixed Concrete Association, Silver Spring,” http://www.nrmca.org/p2p/, last accessed July 28, 2014). One of the challenges in successfully implementing performance-based specifications is the existence and use of reliable test methods and specification criteria that can measure the potential durability of concrete mixtures and provide the expected service life. A state pooled fund research project (TPF-5 (179), 2014, “Evaluation of Test Methods for Permeability (Transport) and Development of Performance Guidelines for Durability,” http://www.pooledfund.org/Details/Study/406, last accessed July 28, 2014) was developed with an objective to propose performance criteria for concrete that will be resistant to penetration of chlorides, cycles of freezing and thawing, and sulfate attack. This paper summarized results pertaining to freeze-thaw resistance. Concrete freeze-thaw (F-T) performance was evaluated by ASTM C666/C666M-15 (AASHTO T161-08 (Standard Method of Test for Resistance of Concrete to Rapid Freezing and Thawing, Standard Specifications for Transportation Materials and Methods of Sampling and Testing, Part 2A: Tests, AASHTO, Washington DC, 2013)) and deicer salt scaling resistance was evaluated by ASTM C672/C672M-12. It was examined whether F-T performance of concrete correlated with results of rapid index tests for fluid transport characteristics of concrete. These tests included the rapid chloride permeability, absorption, and initial and secondary sorptivity. The impact of degree of saturation on the F-T resistance of concrete was also explored. Criteria for F-T resistant concrete mixtures depending on type of exposure were suggested.

Comparative study of attrition measurements of commercial FCC catalysts by ASTM fluidized bed and jet cup test methods

Catalyst loss due to fines generation by attrition is a major problem in refinery fluid catalytic cracking (FCC) units as it impacts inventory loss. Attrition resistance of catalyst is one of the critical parameter in catalyst selection for a FCC unit. ASTM D5757 fluidized bed attrition test is the most commonly used attrition resistance test method to rank FCC catalysts and additives. In the present study, catalyst attrition tests were performed for FCC catalysts using an ASTM fluidized bed, cylindrical jet cup and conical jet cup. Performance ranking shows that attrition index obtained by these tests vary, but the order of ranking remains unchanged for ASTM fluidized bed and conical jet cup test methods as compared to cylindrical jet cup test. The investigation conducted here shows that morphology of attrited fresh FCC catalyst using conical jet cup was found to be similar to plant equilibrium catalyst and also takes less attrition time relative to ASTM fluidized bed.

Issues of standardizing requirements for resistance and strength of railroad automation and signaling systems used in high-speed railways versus external mechanical impact

We discuss the problems of adaptation of requirements for resistance and strength versus external mechanical impact for railroad automation and signaling systems used for Russian high-speed railways. We present an analysis of the requirements and test methods for resistance and strength versus external mechanical impact for railway railroad automation and signaling systems in the current Russian standards. Based on the classification of automation and signaling equipment, the requirements and tests are compared to the similar ones of the European standards used for the design of high-speed railway railroad automation and signaling systems. It is proven necessary to change the mechanical strength requirements imposed by Russian standards in the design of railway railroad automation and signaling systems. We considered the possibility of adaptation of requirements and test methods for railroad automation and signaling systems in the present Russian standards to the problems of design of high-speed railway equipment. In this paper, we provide recommendations for designers on how to select the requirements for resistance and strength versus external mechanical impact and test methods for railroad automation and signaling systems used in high-speed railways.

The Effect Of Sulphuric Acid on The Properties of Random Glass Fiber Polyester Composite

Many supplementary investigations are necessary to accomplish the central demand for a chemical resistance test method of glass fiber reinforced resins. The effect of sulfuric acid (H 2 SO 4 - concentration 10%) on mechanical and chemical properties of malti layers random glass fiber reinforced with polyester resin composite were studied. The samples were immersed on the chemicals for six weeks. The effect of the sulfuric acid on the mechanical properties (tensile, bending, hardness) and physical properties (absorbility) has been studied on the random glass fiber polyester composite. The results showed the mechanical properties in most cases decreased such as the tensile, bending and hardness and the absorbility 5.3%.

Fire performance of sandwich wall assemblies

Abstract Fire performance is often identified as a difficult obstacle to overcome in designing lightweight sandwich panels suitable for use in building applications. Fireproofing generally increases the weight and cost of sandwich panels, reducing the field of application of such solutions. This study presents the fire performance evaluation of different non-loadbearing sandwich wall assemblies, based on the fire resistance test methods recommended by EN 13501-2, EN 1363-1 and EN 1364-1. The main objectives of the present study are: (i) to evaluate the fire performance of different core materials; (ii) to evaluate the fire performance of different fireproofing materials; (iii) to classify the fire resistance of different wall assemblies; and (iv) to design a sandwich panel which withstands a 60 min fire exposure without compromising its integrity (E) and thermal insulation (I) capabilities. Expanded polystyrene foam (EPS), polyethylene terephthalate foam (PET), cork agglomerate (CA) and stone wool (SW) were tested as core materials. Fireproofing gypsum boards (FG) and magnesium oxide boards (MGO) were tested as fireproofing materials. The skins of all sandwich panels tested were glass fibre reinforced polymers (GFRP). Cork agglomerate cores exhibited the lowest thermal decomposition rate under fire exposure and cork agglomerate core sandwich wall assemblies proved to withstand fire exposure for the intended duration, presenting the required performance, even dismissing the use of fireproofing boards.

Damage sensing and fracture detection of CNT paste using electrical resistance measurements

The damage sensing properties of carbon nanotube (CNT) paste were investigated as an easy means of detecting cracking. 1wt% CNT paste was fabricated with different epoxy formulations and hardeners (amino and polyamide types) for use in stress sensing tests. The inherent properties of epoxy resins with the different hardeners were compared for different CNT paste applications. An electrical resistance test method was used to evaluate the state of dispersion of the CNT in the epoxy matrices. In the damage sensing tests, 30wt% CF/PP composites were used as the base materials because the polypropylene (PP) has a low crack resistance. In the damage sensing tests an artificial crack was introduce first in the 30wt% CF/PP composites. Then this crack was filled with CNT paste for the evaluation of crack extension and fracture. It was observed that when fracture occurred at the interface between CF/PP composite and the CNT paste the electrical resistance of the test specimen underwent a sudden jump. The changes in electrical resistance facilitated the detection of fracture and crack extension in the CF/PP composites. Additionally, layers of CNT paste was spread on CF/PP composite specimen at three different locations. As these specimens were tested in tension the location of damage in the in the CF/PP composites could also be identified by following the changes in electrical resistance. CNT paste was feasible to repair crack region by blunting due to the stress transfer through crack interface. The tests revealed that CNT pastes based on amino type epoxy was better for this damage detection than the polyamide type, at least in part due to its enhanced dispersion.

High Prevalence of HIV Low Abundance Drug-Resistant Variants in a Treatment-Naive Population in North Rift Kenya.

The advent of antiretroviral treatment (ART) has resulted in a dramatic reduction in AIDS-related morbidity and mortality. However, the emergence and spread of antiretroviral drug resistance (DR) threaten to negatively impact treatment regimens and compromise efforts to control the epidemic. It is recommended that surveillance of drug resistance occur in conjunction with scale-up efforts to ensure that appropriate first-line therapy is offered relative to the resistance that exists. However, standard resistance testing methods used in Sub-Saharan Africa rely on techniques that do not include low abundance DR variants (LADRVs) that have been documented to contribute to treatment failure. The use of next generation sequencing (NGS) has been shown to be more sensitive to LADRVS. We have carried out a preliminary investigation using NGS to determine the prevalence of LDRVS among a drug-naive population in North Rift Kenya. Antiretroviral-naive patients attending a care clinic in North Rift Kenya were requested to provide and with consent provided blood samples for DR analysis. DNA was extracted and amplified and nested PCR was conducted on the pol RT region using primers tagged with multiplex identifiers (MID). Resulting PCR amplicons were purified, quantified, and pyrosequenced using a GS FLX Titanium PicoTiterPlate (Roche). Valid pyrosequencing reads were aligned with HXB-2 and the frequency and distribution of nucleotide and amino acid changes were determined using an in-house Perl script. DR mutations were identified using the IAS-USA HIV DR mutation database. Sixty samples were successfully sequenced of which 26 were subtype A, 9 were subtype D, 2 were subtype C, and the remaining were recombinants. Forty-six (76.6%) had at least one drug resistance mutation, with 25 (41.6%) indicated as major and the remaining 21 (35%) indicated as minor. The most prevalent mutation was NRTI position K219Q/R (11/46, 24%) followed by NRTI M184V (5/46, 11%) and NNRTI K103N (4/46, 9%). Our use of NGS technology revealed a high prevalence of LADRVs among drug-naive populations in Kenya, a region with predominantly non-B subtypes. The impact of these mutations on the clinical outcome of ART can be ascertained only through long-term follow-up.

A more reliable measurement method for metal/graphene contact resistance

The contact resistance of metal/graphene is becoming a major limiting factor for graphene devices. Among various kinds of contact resistance test methods, the transmission line model is the most common approach to extract contact resistance in graphene devices. However, experiments show that in some cases there exists large inaccuracy and instability using this method. In this study, we added a cross-bridge structure at the terminal of the transmission line as a supporting test. This modified transmission line measurement structure can easily compare not only the transmission line and Kelvin contact resistance, getting a more reliable value, but also the other contact-related parameters, such as specific contact resistivity, transfer length and the graphene sheet resistance under and outside contact metal at the same time. The new measurement test is very helpful in enabling us to study the contact property accurately. The specific contact resistivity in our experiment is in the range of 2.0 × 10−6 Ω · cm2 and 3.0 × 10−6 Ω · cm2 at room temperature. With the temperature decreasing from 290 K to 60 K, the transfer length fluctuates around 1.7 μm, and the specific contact resistivity reduces to less than 2.0 × 10−6 Ω · cm2.

A comparative evaluation of floor slip resistance test methods

Floor slipperiness is among the most influential parameters affecting the life safety of users. However, slip resistance coefficients determined using some methods do not correspond well to the perception of slipperiness by real users. From a life safety standpoint, a suitable test method for the slip resistance of a floor surface reflects slipperiness as sensed by users. We compared the results of three slip resistance test methods and their correspondence with sensed slipperiness as reported by users. The JIS A 1454 test method was found to be a better test of slip resistance than EN 13893 and ASTM D 2047.

Direct current resistance testing methods of carbon fibre reinforced polymer

An experiment platform was established for direct current resistance testing methods of carbon fibre reinforced polymer composites in this paper. Drastic differences have been found in the volume resistance of carbon fibre reinforced polymers between the theoretical values and testing values obtained with a classic three-electrode testing method for solid dielectric materials. Thus, on the basis of the experimental circuit and structures of carbon fibre reinforced polymers, an improved three-electrode testing method was put forward. The experimental results, which reflect the electric characteristics, surface coating materials and internal layer structures of carbon fibre reinforced polymers were subsequently obtained and can be well explained by the inferred conduction model, in which the electric field extension and surface current effect were considered comprehensively. This work provides a theoretical support for further research of electric characteristics, thermal degradation and weight loss of carbon fibre reinforced polymers and also lays a solid foundation for its wide applications in aerospace industries.

Comparative Analysis of Methods for Testing Materials for Fatigue Cracking Resistance

The conventional methods of testing for fatigue cracking resistance (compact samples) are compared with testing with a constant amplitude of the stress intensity factor (DCB samples). Examples are presented of the effect of the ambient environment on the growth rate of a crack in a DCB sample and constant growth rate of a crack in a double beam sample with constant amplitude of the stress intensity factor. The advantages and limitations of the testing methods studied are discussed. It is noted that DCB samples and double-beam samples with crack length independent stress intensity factor hold promise for studying the regularities of crack growth not only under cyclic but also under prolonged static loading.

Transmission of HIV drug resistance: lessons from sensitive screening assays.

The review discusses new technologies for the sensitive detection of HIV drug resistance, with a focus on applications in antiretroviral treatment (ART)-naïve populations. Conventional sequencing is well established for detecting HIV drug resistance in routine care and guides optimal treatment selection in patients starting ART. Access to conventional sequencing is nearly universal in Western countries, but remains limited in Asia, Latin America, and Africa. Technological advances now allow detection of resistance with greatly improved sensitivity compared with conventional sequencing, variably increasing the yield of resistance testing in ART-naïve populations. There is strong cumulative evidence from retrospective studies that sensitive detection of resistant mutants in baseline plasma samples lacking resistance by conventional sequencing more than doubles the risk of virological failure after starting efavirenz-based or nevirapine-based ART. Sensitive resistance testing methods are mainly confined to research applications and in this context have provided great insight into the dynamics of drug resistance development, persistence, and transmission. Adoption in care settings is becoming increasingly possible, although important challenges remain. Platforms for diagnostic use must undergo technical improvements to ensure good performance and ease of use, and clinical validation is required to ensure utility.

Towards more representative test methods for corrosion resistance of PEMFC metallic bipolar plates

Metallic bipolar plates are of increasing interest to automotive polymer electrolyte membrane fuel cell (PEMFC) manufacturers due to their low cost, high power density, ease of manufacture, high conductivity and good mechanical properties but minimising the undesirable effects of corrosion remains a key challenge. Unfortunately, reliable assessment of the applicability of stainless steels with a range of coatings and surface treatments has been hampered by a lack of representative ex situ test methods. Here we characterise the local environment experienced by a bipolar plate during fuel cell operation via in situ measurement of pH and corrosion potential for an uncoated 316L stainless steel bipolar plate in a single cell PEMFC. We demonstrate that the degradation mode is more akin to corrosion in relatively dilute thin liquid layers, rather than the fully immersed conditions employed in conventional ex situ screening tests. A key observation is that the corrosion potential of the bipolar plate is only weakly coupled to the potential of the nearest Pt electrode due to the low ionic conductivity of the discontinuous aqueous phase in the gas diffusion layer (GDL). However, localised polarisation of the steel can occur in the presence of oxygen as a result of galvanic coupling with the carbon GDL at wetted interfaces, a process which may be enhanced by the creviced geometry. The implications for development of more representative ex situ test protocols are discussed.

Correlation of fracture resistance of molar teeth with weight

Background: The aim of this study was to determine a standardizing model for fracture resistance test methods in which molar teeth are used. Materials and Methods: Fifty freshly extracted human mandibular molar teeth were selected. Each tooth was numbered and data were obtained by measuring the mesiodistal (MD) and buccolingual (BL) dimensions, length, and weight. Tests for fracture strength were performed using a universal testing machine, and for each sample, the force at the time of fracture was recorded in Newton. The correlations of the MD and BL dimensions, lengths, and weights of the teeth to the fracture strength values were evaluated using the Pearson correlation coefficient. Results: Significant correlations were not observed between the fracture strength values and MD dimensions (r = 0.055, P > 0.05), BL dimensions (r = 0.074, P > 0.05), and lengths of the teeth (r = 0.017, P > 0.05); however, they were observed with the weights of the teeth (r = 0.312, P < 0.05). Conclusions: The fracture resistance of molar teeth increases as their weights increases. These weights should be standardized during fracture resistance studies when distributing sample molar teeth into the study groups.