Minimum Acceptable Value Research Articles

Structure, texture, and mechanical properties of an MA2-1hp magnesium alloy after two-stage equal-channel angular pressing and intermediate annealing

The effect of two-stage equal-channel angular pressing (ECAP) on the microstructure, the texture, and the mechanical properties of an MA2-1hp magnesium alloy is analyzed. ECAP leads to the formation of a submicrocrystalline structure with an average grain size of 640 nm, which includes Mg17Al12 phase particles with an average grain size of 240 nm and a volume fracture of 5.5%. A scattered tilted basal texture forms after ECAP, and its experimental pole figures are used for calculating orientation distribution functions and determining the volume fractions of the main orientations and the Schmid factors for different deformation systems. An increased activation of basal slip is found after both the first and the second stages of ECAP. As a result of two-stage ECAP, the strength properties of the alloy that correspond to the minimum acceptable values achieved by direct compression are obtained. Ductility is 44 and 18% after the first stage of ECAP plus subsequent annealing and after the second stage, respectively, which is almost four and two times higher than the initial value. The resulting strength mechanical properties of the alloy after the first and the second ECAP stages are analyzed using the Hall-Petch relation.

CV-joint remanufacturing parameter optimization

Quality assessment process is based on a standard procedure. These standards are developed as a combined effort. It requires deep knowledge about structural material in addition to component`s behavior under external loads. Remanufactured components pose another difficulty to assess their quality in the form of unknown usage rate. This paper represents optimization of quality assessment criteria for remanufactured CV-joints. Working surface hardness of the CV-joint elements is measured at certain depth interval. A minimum acceptable surface hardness value for the BJ-outer joint elements is suggested based on existing research. Remanufactured CV-joint Housing, Inner race and Cage surface machining steps are studied and machining parameter optimization is performed through laboratory based durability test results. The test results of optimized machining parameters are compared with the test results of unmachined test samples. Mean-time-to-failure is calculated along with Weibull distribution parameters. Also, Birfield joint inner race bending and rotating torque are measured and standard parameters for remanufactured CV-joint are determined. Those quality assessment criteria for remanufactured CV-joints are developed.

Decision-making in the manufacturing environment using a value-risk graph

A value-risk based decision-making tool is proposed for performance assessment of manufacturing scenarios. For this purpose, values (i.e. qualitative objective statements) and concerns (i.e. qualitative risk statements) of stakeholders in any given manufacturing scenario are first identified and are made explicit via objective and risk modeling. Next, performance and risk measures are derived from the corresponding objective and risk models to evaluate the scenario under study. After that, upper and lower bounds, and target value is defined for each measure in order to determine goals and constraints for the given scenario. Because of the multidimensionality nature of performance, the identified objectives and risks, and so, their corresponding measures are usually numerous and heterogeneous in nature. These measures are therefore consolidated to obtain a global performance indicator of value and global indicator of risk while keeping in views the inter-criteria influences. Finally, the global indicators are employed to develop minimum acceptable value and maximum acceptable risk for the scenario under study and plotted on the VR-Graph to demarcate zones of "highly desirable", "feasible", "and risky" as well as the "unacceptable" one. The global scores of the indicators: (value-risk) pair of the actual scenario is then plotted on the defined VR-Graph to facilitate decision-making by rendering the scenarios' performance more visible and clearer. The proposed decision-making tool is illustrated with an example from manufacturing setup in the process context but it can be extended to product or systems evaluation.

Assessing the Proportion of Conformance of a Process from a Bayesian Perspective

The question of assessing the capability of a process to produce according to some specifications connected with a measurable characteristic (X) of the items produced through it is of great importance in statistical process control. These specifications consist of the lower specification limit (L), which is the minimum acceptable process value; the upper specification limit (U), which is the maximum acceptable process value; and the target value (T), which coincides with the most desirable process value. Process capability indices constitute the most commonly used tool for measuring process capability. Every process capability index combines the values of process specifications, with those of the parameters of the process, that is, the mean (μ) and the standard deviation (σ), takes non-negative values, and its large values provide evidence of a capable process. The development and the estimation of a process capability index simplify substantially when the studied process is assumed to be normally distributed and most of the work that has appeared in the literature on this issue has been based on this assumption. For more details on various aspects of process capability indices, such as properties, estimation techniques, and interrelations, the reader

Value-Risk Graph: A decision-making tool for supply chain and industrial system engineering

A value-risk based decision-making tool is proposed for performance evaluation of industrial systems at build-time. For this purpose, stakeholders’ expectations and concerns, respectively expressed in terms of objectives and risks, are identified and transformed into global value and risk indicators using principles, tools and techniques of performance measurement, risk assessment and decision-making disciplines. Moreover, minimum acceptable value and maximum acceptable risk for the scenario understudy are computed. They are then used to demarcate zones of “highly feasible”, “feasible”, “risky” as well as “unacceptable” situations on the proposed Value-Risk Graph in order to facilitate the decision-making process. The proposed decision-making tool is illustrated with an example dealing with manufacturing process design but it can be applied to any kind of product or system evaluation.

Groundwater Quality Assessment for Drinking and Irrigation Purposes in Obuasi Municipality of Ghana, A Preliminary Study

Groundwater quality of the Obuasi municipality was assessed to understand the contamination processes due to the presence of various contaminant sources and complicated geochemical processes and the suitability of groundwater for irrigation and drinking purpose for a sustainable agriculture and basic human needs. Water samples were collected during the raining season when a rise in water table was expected and during the dry season. They were analyzed for major cations and anions. Parameters like sodium adsorption ratio, % sodium, electrical conductivity, total hardness, total dissolve solutes and stoechiometric relations were calculated on the basis of chemical data. A questionnaire was also used to investigate perception of consumers on taste and odour. Comparison of the concentration of the chemical constituents with World Health Organization (WHO) drinking water standards of 2004 and various classifications show that present status of groundwater in Obuasi is good for drinking and irrigation purposes. Concentrations of major cations and anions in the groundwater systems vary spatially and temporally. Abundance of these anions is in the following order: $Ca^{2+}\>>\>Na^+\>>\>Mg^{2+}\>>\>K^+ = HCO_3^-\>>\>Cl^-\>>\> SO_4^{2-}\>>\>H_2SiO_4\>>\>Br^-\>>\>PO_4^{2-}\>>\>F^-$. In terms of rainy season impact, Obuasi groundwater shows dilution and flushing, however, samples show excessive leaching of different chemical components into the groundwater system leading to the enrichment of different anions and cations and this indicate pollution from extraneous sources. No clear correlation between the quality parameters and perceived quality in terms of satisfactory taste response were obtained at electrical conductivity values lower than the threshold minimum acceptable value.

Geotechnical Evaluation of Reddish Brown Tropical Soils

Laboratory investigations were carried out on reddish brown tropical soils from Moniya, Ibadan Southwestern Nigeria to determine the basic unconfined compressive strength of the soil samples which is an important factor to be considered when considering materials as liners in waste containment structure. Clay mineralogy, major element geochemical analyses were carried out by means of X-ray diffractometry and X-ray fluorescence spectrometry respectively. The engineering tests such as sieve size analyses, Atterberg limits, natural moisture contents, specific gravity and compaction using four different compactive efforts namely reduced proctor, standard proctor, West African standard and modified proctor. The tests were carried out in line with the procedures of the British standard 1377 of 1990 and Head of 1992. The soils were found to contain kaolinite as the major minerals with some mixtures of smectite, muscovite, halloysite, quartzite, biotite and aluminium phosphate. Values of the unconfined compressive strength obtained within 12.5 and 22.5% moulding water contents equal to or greater than 200 kN/m2 which is the minimum acceptable value required for containment facilities. The maximum dry density, Mg/m3 ranged between 1.68 and 1.98 while Optimum moisture content, % ranged between 12.3 and 21.2. Hence, unconfined compressive strength values were found to be greater than 200 kN/m2 at dry unit weight of 16.20 kN/m3 especially when WAS and modified proctor compactive efforts were used which met the minimum required unconfined compressive strength of 200 kN/m2 for hydraulic barriers in waste containment facilities.

Limites de confiança para variáveis em análises de sementes de espécies florestais exóticas

Este trabalho teve por objetivo propor padrões para a padronização dos índices das análises de sementes de espécies florestais. Para tanto, foram utilizados resultados de análises de sementes dessas espécies a partir do ano de 1997 até 2007, pertencentes aos arquivos do Laboratório de Análise de Sementes da Fundação Estadual de Pesquisa Agropecuária - FEPAGRO, localizado em Santa Maria, RS. Os limites de confiabilidade foram construídos a partir de uma análise de normalidade dos dados e da utilização do critério do pseudossigma. Os limites de confiança estabeleceram os valores mínimos aceitáveis para que um lote de sementes seja comercializado, propondo que valores de germinação dentro dos limites de confiabilidade muito baixos ou baixos devem ser descartados, pois não apresentam índices germinativos aceitáveis.

Definition of the procedure to determine the suitability and durability of an anti-graffiti product for application on cultural heritage porous materials

Abstract Anti-graffiti protection is becoming a common practice in many urban buildings, especially in areas of social decay. When Cultural Heritage objects are affected by graffiti, the application of anti-graffiti products can result not only in an unsatisfactory result but also in an irreversible damage of an invaluable cost. The materials commonly found in these constructions are very frequently porous and present different types of decay forms. For this reason, the protection of these materials should be carefully considered. This paper proposes a criterion to decide on the suitability and durability of an anti-graffiti product prior to its application in a porous surface of a protected building. Performance classifications are defined for a series of properties including colour and gloss, and hydric and durability properties, and minimum acceptable values or reductions in these properties are recommended.

Discussion on the influence of truncation of ground motion residual distribution on probabilistic seismic hazard assessment

Recent studies on assessment of a very low annual probability of exceeding (APE) ground motions, 10−4 or less, have highlighted the importance of the upper bound of ground motions when very low probability results are acquired. The truncation level adopted in probabilistic seismic hazard analysis (PSHA) should be determined by an aleatory uncertainty model (i.e., distribution model) of ground motions and the possible maximum and minimum ground motion values of a specific earthquake. However, at the present time, it is impossible to establish the upper bound model for ground motions based on the source characteristics and/or ground motion propagation. McGuire suggested a truncation level be fixed at a number of ɛ = 6, or the distribution of residuals be truncated in such a manner that site intensity cannot be greater than the epicenter intensity. This study aims to find a reasonable and feasible truncation level to be used in PSHA when the physical mechanism is not available to find the extreme ground motion. A mathematical analysis of the influence of the truncation level on PSHA, case studies of sites in different seismotectonic settings, and a distribution analysis of ground motion residuals are conducted in this study. It is concluded that ɛ = 4 is the minimum acceptable value for engineering applications for APEs within 0.002 to 10−4, and for low APEs, such as 10−5 and 10−6, the value of e should be no less than 5 in most regions of China.

Padrões para germinação, pureza, umidade e peso de mil sementes em análises de sementes de espécies florestais nativas do Rio Grande do Sul

O presente trabalho teve como objetivo propor padrões de confiabilidade, em relação à germinação, pureza, peso de mil sementes e grau de umidade das sementes, visando ao controle de qualidade das análises de sementes de espécies florestais. Para tanto, foram utilizados resultados de análises de sementes de espécies florestais em laboratório, a partir do ano de 1997 até 2007, obtidos dos arquivos do Laboratório de Análise de Sementes da Fundação Estadual de Pesquisa Agropecuária do Estado do Rio Grande do Sul. Os padrões de confiabilidade foram construídos com base em uma análise de normalidade dos dados e da utilização do critério do pseudossigma. Os limites se mostraram eficientes no estabelecimento do valor mínimo aceitável para que um lote de sementes seja comercializado, propondo que valores de germinação dentro dos limites de confiabilidade baixos devem ser descartados, pois não apresentam índices germinativos aceitáveis.

Infertility in a beef bull due to a failure in the capacitation process

The objective of this case report was to identify the cause of apparent idiopathic infertility in a Red Angus (beef) bull. Semen was collected by electroejaculation and submitted to a series of assays, including evaluation of sperm motility by computer-assisted sperm analysis (CASA), sperm morphology and DNA integrity, semen cryopreservation, AI, IVF, induction of the acrosome reaction, and determination of the level of sperm proteins associated with bull fertility potential. Total (92 ± 2%) and progressive (79 ± 4%) sperm motility; sperm concentration (1647 ± 429 × 106 sperm/mL); proportions of morphologically normal sperm (83 ± 6%) and DNA integrity (96 ± 2), and acrosome-intact sperm (64 ± 4%) exceeded minimum acceptable values. Frozen sperm had good total (58.7 ± 6.7%) and progressive (43.9 ± 9.2%) motility immediately after thawing. However, AI of 16 heifers resulted in no pregnancies and blastocyst production rate (following IVF using sperm from this infertile bull) was nearly identical to that produced using dead sperm (a control of parthenogenesis; 2 ± 2 and 2 ± 3%; respectively P < 0.05). Treatment with a calcium ionophore (A23187) failed to induce the acrosome reaction in sperm from the infertile bull (P < 0.05). Evaluation of several proteins associated with the fertility potential of bulls revealed that the level of Binder Sperm Protein-1 (BSP1), known to be associated with the capacitation process, was much greater on sperm from the infertile bull compared to that of his sire. In conclusion, we inferred that the idiopathic infertility in this bull was caused by a failure to complete the capacitation process.

Linear Mixed-Effects Models for Paint Pavement-Marking Retroreflectivity Data

The objective of this paper is to present an improved paint pavement-marking retroreflectivity degradation model. Previous degradation-modeling methods were reviewed and studied. The paint-marking retroreflectivity data were collected on 25 two-lane rural highways in North Carolina from November 2007 to May 2010. A linear mixed-effects model (LMEM) was selected as most appropriate for the paint-marking retroreflectivity data. The LMEM took into account the correlation among repeated measurements of the data set and produced more accurate predictions than other methods. LMEMs were established for white edge and yellow center paint pavement markings. The LMEM results showed that the estimated white edge pavement marking life cycle is 37.5 months and yellow center marking life cycle is 38.9 months on average when using 100 and 65 mcd/m2/lx as the minimum acceptable retroreflectivity values for white and yellow paint markings. A model comparison indicated that the LMEM provided a more accurate prediction tha...

Kinematics of galaxies in compact groups

We obtained new Fabry-Perot data cubes and derived velocity fields, monochromatic, and velocity dispersion maps for 28 galaxies in the Hickson compact groups 37, 40, 47, 49, 54, 56, 68, 79, and 93. We also derived rotation curves for 9 of the studied galaxies, 6 of which are strongly asymmetric. Combining these new data with previously published 2D kinematic maps of compact group galaxies, we investigated the differences between the kinematic and morphological position angles for a sample of 46 galaxies. We find that one third of the unbarred compact group galaxies have position angle misalignments between the stellar and gaseous components. This and the asymmetric rotation curves are clear signatures of kinematic perturbations, probably because of interactions among compact group galaxies. A comparison between the <i>B<i/>-band Tully-Fisher relation for compact group galaxies and for the GHASP field-galaxy sample shows that, despite the high fraction of compact group galaxies with asymmetric rotation curves, these lay on the TF relation defined by galaxies in less dense environments, although with more scatter. This agrees with previous results, but now confirmed for a larger sample of 41 galaxies. We confirm the tendency for compact group galaxies at the low-mass end of the Tully-Fisher relation (HCG 49b, 89d, 96c, 96d, and 100c) to have either a magnitude that is too bright for its mass (suggesting brightening by star formation) and/or a low maximum rotational velocity for its luminosity (suggesting tidal stripping). These galaxies are outside the Tully Fisher relation at the 1<i>σ<i/> level, even when the minimum acceptable values of inclinations are used to compute their maximum velocities. Including such galaxies with <i>v<i/> < 100 km s<sup>-1<sup/> in the determination of the zero point and slope of the compact group <i>B<i/>-band Tully-Fisher relation would strongly change the fit, making it different from the relation for field galaxies, which has to be kept in mind when studying scaling relations of interacting galaxies, especially at high redshifts.

Interrater Reliability of Manual Pavement Distress Evaluations

Many government agencies are faced with the challenge of pavement evaluation and maintenance as part of their pavement management systems. These agencies perform or contract manual or automated distress surveys over the pavement network to monitor the structure performance and obtain the necessary data to calculate pavement condition indexes. Although manual distress ratings are done according to well-defined criteria, a certain amount of subjectivity and the experience of the raters have an undoubted influence on the ratings. This study proposes a new approach to estimate the interrater or intercrew reliability for manual or semiautomated distress data collection. The proposed analysis acknowledges that a certain degree of variability in the visual distress ratings is likely to occur and, thus, minimum acceptable values of complete and partial agreements of the crews or raters are suggested. The statistical approach to validate the level of agreement between the ratings of two raters or crews is based on the use of the chi-square distribution to test hypotheses about multinomial experiments.

McMonnies Questionnaire: Enhancing Screening for Dry Eye Syndromes with Rasch Analysis

To determine, by using Rasch analysis, whether the McMonnies questionnaire possesses the properties of a measure and whether screening for dry eye syndromes (DESs) can be enhanced by using different scoring approaches. The questionnaire was self-administered by 43 female Sjögren syndrome patients (>45 years) recruited from a specialized rheumatology clinic and 140 age-matched control subjects. Data were scaled by using Rasch analysis and were assessed for response category behavior and ability to reliably discriminate between severity of the participant's dry eye symptoms (i.e., person separation reliability; minimum acceptable value, 0.80). Standard summary statistics of screening performance were calculated for raw and Rasch-scaled scores from receiver-operating characteristic analysis including area under the curve (AUC). Best predictors (i.e., questions) from a discriminant analysis were used to calculate a discriminant function for both Rasch-scaled and raw scores. Response categories were not used as intended, necessitating a collapse of categories. Person separation reliability was inadequate (0.75). A Rasch-scaled discriminant cutoff score of -2.29 logits from seven items provided an AUC of 0.99 with 95% sensitivity. However, discriminant raw score from modification in the scoring of a question (e.g., use of medications), used as one rather than multiple questions, provided an AUC (0.97) that was not significantly different (z = 1.11, P = 0.27), with 98% sensitivity, and required only two questions. In this population, the McMonnies questionnaire does not function as a measure. However, various scoring methods can be used to efficiently screen for DES.

Activities of Daily Vision Scale: What Do the Subscales Measure?

Previous Rasch analysis of the Activities of Daily Vision Scale (ADVS) did not address psychometric properties of its subscales or provide detailed assessment of dimensionality (whether the ADVS measures one or multiple constructs). This study was designed to examine these properties. Two hundred thirty-two participants (mean age, 74.2 years) awaiting cataract surgery self-administered the ADVS. Rasch analysis was used to assess the ADVS and its five subscales for unidimensionality (by principal components analysis, [PCA]), precision by person separation (discrimination between strata of participant ability), and targeting (matching of item difficulty to participant ability). Adequate person separation (minimum acceptable value, 2.0) is the fundamental requirement for measurement. Only the near vision subscale had adequate measurement properties (person separation, 2.30). The entire ADVS showed a misfit to the Rasch model and lacked unidimensionality. PCA confirmed the presence of two additional traits-driving and glare disability-but neither possessed adequate person separation when assessed individually. Deleting these traits restored unidimensionality, but additional items misfit, necessitating item reduction. Finally, an eight-item ADVS-Near Vision Scale showed good fit and unidimensionality. Its contents were identical with the original near vision subscale. Targeting was suboptimal (2.30 logits). Only one subscale, near vision, met the criteria for measurement. The revised eight-item ADVS-Near Vision subscale is a unidimensional measure of visual disability in cataract patients with mild visual disability. However, it is limited by measurement of near visual ability only. For more comprehensive measurement of visual disability, other questionnaires such as Catquest-9SF are preferable for cataract surgery outcomes assessment.

Synthesis of Distillation Column Sequences for Nonsharp Separations

In this paper an algorithm to generate all possible distillation column sequences for a nonsharp separation of c components to m multicomponent as well as pure desired products, based on the product specifications, is presented. Each desired product is defined by the minimum and maximum acceptable values of product rates as well as the concentration of each component. The possible sequences are generated by the introduction of a separation matrix. In the proposed algorithm each sequence can include between 1 and c − 1 simple and/or complex distillation columns and bypass streams. The sequences with less than c − 1 distillation columns can be generated systematically by the proposed algorithm. Also, a design strategy has been proposed for the optimization of the sequences. This algorithm has been used for a nonsharp separation example. A sequence with less than c − 1 number of distillation columns and bypass streams is selected as the optimum structure for this example. This optimum sequence can cause sign...

Analysis of the properties of a steering shaft used as a back-up for a steer-by-wire system during system failure

An analysis is presented to determine the best selection criteria for the properties of a steering shaft to be used as a back-up apparatus for a steer-by-wire (SBW) system during system failure. The properties of interest are the steering-shaft stiffness and its damping coefficient. A mathematical model representing the failed state of an SBW system is derived, and a set of experiments to validate the model is presented. Once the model had been validated, further predictions of the car's handling behaviour for a range of steering-shaft properties and different road speeds were completed by simulations in MATLAB/Simulink. A minimum stiffness which did not cause the car to become unstable owing to overshoot was determined, and the minimum acceptable damping coefficient value was derived. It is concluded that the suggested stiffness and damping coefficient values increased the steering ratio, and the results of further investigations are presented, which confirm that the vehicle is safe to be driven in the event of SBW system failure if the recommended shaft properties are used.

Agronomic and economic performance of reservoir sediment for rehabilitating degraded soils in Northern Ethiopia

Nutrient export through sediment is, often, not given due attention in improving the fertility of soils. A Randomized Complete Block Design (RCBD) (replicated three times) was conducted to assess the effect of sediment, collected from a microdam, on the yield of a local wheat cultivar (Triticum aestivum) grown on a Luvisol and a Vertisol during cropping season of 2003 and 2004 in Tigray, Ethiopia. In the first season, the treatments consisted of applying 34.3 Mg sediment ha−1 (T1), 0.1 Mg urea ha−1 (T2), 4 Mg manure ha−1 (T3) and a control plot (T4). The experiment was repeated in the 2004 cropping season using the same indicator crop but without the use of T1 and T3 inputs to evaluate the residual effect of these treatments on crop productivity. Plant height, plant density, spike length, straw and grain yield were compared among the treatments. After harvest, surface soil (0–25 cm) samples were taken and analyzed for total Nitrogen (Ntot), available Phosphorous (P), Soil Organic Carbon (SOC), Cation Exchange Capacity (CEC), and porosity to examine treatments effect on these soil properties. Higher CEC, exchangeable bases, SOC, Ntot, available P and micronutrients except Cu characterized sediment compared to the two soils used. Application of sediment increased the average grain and straw yield of wheat by 72% and 12%, respectively, in the Luvisol, and by 38% and 23%, respectively, in the Vertisol relative to the control. However, the application of sediment didn’t change the physicochemical properties of the Vertisol, but in the Luvisol CEC and available P were increased significantly. Like manure, sediment provided marginal rate of return above the minimum acceptable value (100%) by farmers, demonstrating the potential of these resources to improve degraded soils and boost farmers’ income.