Search results for: step-stress partially accelerated life tests

Authors: Wei Yongxiang, Zhu Haoyue, Tang Heng, Yuan Qunwei

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In order to study the preparation method of gear fatigue load spectrum for loaders, the load signal of four typical working conditions of loader is collected. The signal that reflects the law of load change is obtained by preprocessing the original signal. The torque of the drive axle is calculated by using the rain flow counting method. According to the operating time ratio of each working condition, the two-dimensional load spectrum based on the real working conditions of the drive axle of loader is established by the cycle extrapolation and synthesis method. The two-dimensional load spectrum is converted into one-dimensional load spectrum by means of the mean of torque equal damage method. Torque amplification includes the maximum load torque of the main reduction gear. Based on the theory of equal damage, the accelerated cycles are calculated. In this way, the load spectrum of the loading condition of the drive axle is prepared to reflect loading condition of the loader. The load spectrum can provide reference for fatigue life test and life prediction of loader drive axle.

Keywords: load spectrum, axle, torque, rain-flow counting method, extrapolation

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Authors: Milad Abolfazli, Milad Bazli

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In this critical review, the topic of how composites maintain their tensile strength when exposed to elevated temperatures will be studied. A comprehensive database of 761 tests have been analyzed and closely examined to study the various factors that affect the strength retention. Conclusions are drawn from the collective research efforts of numerous scholars who have investigated this subject. Through the analysis of these tests, the relationships between the tensile strength retention and various effective factors are investigated. This review is meant to be a practical resource for researchers and engineers. It provides valuable information that can guide the development of composites tailored for high-temperature applications. By offering a deeper understanding of how composites behave in extreme heat, the paper contributes to the advancement of materials science and engineering.

Keywords: tesnile tests, high temperatures, FRP composites, mechanical perfomance

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Authors: Viliam Makis, Farnoosh Naderkhani, Leila Jafari

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In this paper, we present a model and an algorithm for the calculation of the optimal control limit, average cost, sample size, and the sampling interval for an optimal Bayesian chart to control the proportion of defective items produced using a semi-Markov decision process approach. Traditional p-chart has been widely used for controlling the proportion of defectives in various kinds of production processes for many years. It is well known that traditional non-Bayesian charts are not optimal, but very few optimal Bayesian control charts have been developed in the literature, mostly considering finite horizon. The objective of this paper is to develop a fast computational algorithm to obtain the optimal parameters of a Bayesian p-chart. The decision problem is formulated in the partially observable framework and the developed algorithm is illustrated by a numerical example.

Keywords: Bayesian control chart, semi-Markov decision process, quality control, partially observable process

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Authors: Nihit Madireddi, P. A. Mahanwar

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We have aimed to produce a self-cleaning transparent polymer coating with polyurethane (PU) matrix as the latter is highly solvent, chemical and weather resistant having good mechanical properties. Nano-silica modified by 1H, 1H, 2H, 2H-perflurooctyltriethoxysilane was incorporated into the PU matrix for attaining self-cleaning ability through hydrophobicity. The modification was confirmed by particle size analysis and scanning electron microscopy (SEM). Thermo-gravimetric (TGA) studies were carried to ascertain the grafting of silane onto the silica. Several coating formulations were prepared by varying the silica loading content and compared to a commercial equivalent. The effect of dispersion and the morphology of the coated films were assessed by SEM analysis. All coating standardized tests like solvent resistance, adhesion, flexibility, acid, alkali, gloss etc. have been performed as per ASTM standards. Water contact angle studies were conducted to analyze the hydrophobic character of the coating. In addition, the coatings were also subjected to salt spray and accelerated weather testing to analyze the durability of the coating.

Keywords: FAS, nano-silica, PU clear coat, self-cleaning

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Authors: Seyed Reza Mirmahdi, Seyedeh Maryam Hashemi Jabali

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This research was conducted to evaluate the effects of group spiritual therapy on increasing the life expectancy and mental health among the elderlies. This was a quasi-experimental research using a pretest-posttest design with a control group conducted over a population including all the elderly people of Tehran in 2012-13. A randomized sampling method was used to select 30 elderly people living in Parham nursing home that were then randomly assigned into two control and experimental groups of 15 people each. The instruments used were Miller’s life expectancy and mental health test (SCL.90.R) standard questionnaires. Individuals in experimental group received 12 sessions of group spiritual therapy while those in control group did not receive any kind of therapy. The tests were performed again for all the subjects (30 individuals) at the end of the experiment. To test the hypotheses, the data collected by questionnaires were analyzed using descriptive methods through relevant tables and charts and also inferential methods through the analysis of covariance using the SPSS software. Results showed that group spiritual therapy leads to a significant increase in both mental health and life expectancy in the experimental group of elderlies living in Parham nursing home compared to those in the control group.

Keywords: spiritual therapy, life expectancy, mental health, elderlies

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Authors: Dwi Endarti, Susi a Kristina, Rizki Noorizzati, Akbar E Nugraha, Fera Maharani, Kika a Putri, Asninda H Azizah, Sausanzahra Angganisaputri, Yunisa Yustikarini

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Cost utility analysis is the most recommended pharmacoeconomic method since it allows widely comparison of cost-effectiveness results from different interventions. The method uses outcome of quality-adjusted life year (QALY) or disability-adjusted life year (DALY). Measurement of QALY requires the data of utility dan life years gained. Utility is measured with the instrument for quality of life measurement such as EQ-5D. Recently, the EQ-5D is available in two versions which are EQ-5D-3L and EQ-5D-5L. This study aimed to compare the EQ-5D-3L and EQ-5D-5L to examine the most suitable version for Indonesian population. This study was an observational study employing cross sectional approach. Data of quality of life measured with EQ-5D-3L and EQ-5D-5L were collected from several groups of population which were respondent with chronic diseases, respondent with acute diseases, and respondent from general population (without illness) in Yogyakarta Municipality, Indonesia. Convenience samples of hypertension patients (83), diabetes mellitus patients (80), and osteoarthritis patients (47), acute respiratory tract infection (81), cephalgia (43), dyspepsia (42), and respondent from general population (293) were recruited in this study. Responses on the 3L and 5L versions of EQ-5D were compared by examining the psychometric properties including agreement, internal consistency, ceiling effect, and convergent validity. Based on psychometric properties tests of EQ-5D-3L dan EQ-5D-5L, EQ-5D-5L tended to have better psychometric properties compared to EQ-5D-3L. Future studies for health related quality of life (HRQOL) measurements for pharmacoeconomic studies in Indonesia should apply EQ-5D-5L.

Keywords: EQ-5D, Health Related Quality of Life, Indonesian Population, Psychometric Properties

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Authors: Swarnalata Sahoo, Smita Mohanty, S. K. Nayak

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Environmentally friendly Polyurethane(PU) synthesis from Castor oil(CO) has been studied extensively. Probably due to high proportion of fatty hydroxy acids and unsaturated bond, CO showed better performance than other oil, can be easily utilized as commercial applications. In this work, cured PU polymers having different –NCO/OH ratio with and without catalyst were synthesized by using partially biobased Isocyanate with castor oil (CO). Curing time has been studied by observing at the time of reaction, which can be confirmed by AT-FTIR. DSC has been studied to monitor the reaction between CO & Isocyanates using non Isothermal process. Curing kinetics have also been studied to investigate the catalytic effect of the NCO / OH ratio of Polyurethane. Adhesion properties were evaluated from Lapshear test. Tg of the PU polymer was evaluated by DSC which can be compared by DMA. Surface Properties were studied by contact angle measurement. Improvement of the interfacial adhesion between the nonpolar surface of Aluminum substrate and the polar adhesive has been studied by modifying surface.

Keywords: polyurethane, partially bio-based isocyanate, castor oil, catalyst

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Authors: Faozia A. S. Abuhtana, Yahia S. Abujnah, Said O. Gnann

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Ultra High Temperature (UHT) processed milk is widely distributed and preferred in numerous countries all over the world due its relatively high quality and long shelf life. Because of the notable high consumption rate of UHT in Libya in addition to negligible studies related to such product on the local level, this study was designed to assess the shelf life of locally produced as well as imported reconstituted sterilized whole milk samples marketed in Tripoli, Libya . Four locally produced vs. three imported brands were used in this study. All samples were stored at room temperature (25± 2C ) for 8 month long period, and subjected to physical, chemical, microbiological and sensory tests. These tests included : measurement of pH, specific gravity, percent acidity, and determination of fat, protein and melamine content. Microbiological tests included total aerobic count, total psychotropic bacteria, total spore forming bacteria and total coliform counts. Results indicated no detection of microbial growth of any type during the study period, in addition to no detection of melamine in all samples. On the other hand, a gradual decline in pH accompanied with gradual increase in % acidity of both locally produced and imported samples was observed. Such changes in both pH and % acidity reached their lowest and highest values respectively during the 24th week of storage. For instance pH values were (6.40, 6.55, 6.55, 6.15) and (6.30, 6.50, 6.20) for local and imported brands respectively. On the other hand, % acidity reached (0.185, 0181, 0170, 0183) and (0180, 0.180, 0.171) at the 24th week for local and imported brands respectively. Similar pattern of decline was also observed in specific gravity, fat and protein content in some local and imported samples especially at later stages of the study. In both cases, some of the recorded pH values, % acidity, sp. gravity and fat content were in violation of the accepted limits set by Libyan standard no. 356 for sterilized milk. Such changes in pH, % acidity and other UHT sterilized milk constituents during storage were coincided with a gradual decrease in the degree of acceptance of the stored milk samples of both types as shown by sensory scores recorded by the panelists. In either case degree of acceptance was significantly low at late stages of storage and most milk samples became relatively unacceptable after the 18th and 20th week for both untrained and trained panelists respectively.

Keywords: UHT milk, shelf life, quality, gravity, bacteria

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Authors: Emine Feyza Şükür, Mevlüt Türköz, Murat Dilmeç, Hüseyin Selçuk Halkacı

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In this study, a warm bulge test system was designed, built and experimentally validated to perform warm bulge tests with all necessary systems. In addition, performance of each sub-system is validated through repeated production and/or test runs as well as through part quality measurements. Validation and performance tests were performed to characterize the repeatability of the system. As a result of these tests, the desired temperature distribution on the sheet metal was obtained by the heating systems and the good repeatability of the bulge tests was obtained. Consequently, this study is expected to provide other researchers and manufacturer with a set of design and process guidelines to develop similar systems.

Keywords: design, test unit, warm bulge test unit, validation test

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Authors: Ekkehard Fehling, Paul Capewell

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In recent years, the importance of masonry glued by polyurethane adhesive has increased. In 2021, the Institute of Structural Engineering of the University of Kassel was commissioned to carry out quasi-static in-plane shear tests on prefabricated brick masonry panel systems with 2K PUR adhesive in order to investigate the load-bearing behavior during earthquakes. In addition to the usual measurement of deformations using displacement transducers, all tests were documented using an optical measuring system (“GOM”), which was used to determine the surface strains and deformations of the test walls. To compare the results with conventional mortar walls, additional reference tests were carried out on test specimens with thin-bed mortar joints. This article summarizes the results of the test program and provides a comparison between the load-bearing behavior of masonry bonded with polyurethane adhesive and thin bed mortar in order to enable realistic non-linear modeling.

Keywords: masonry, shear tests, in-plane, polyurethane adhesive

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Authors: Nur Farizah Binte Mohd Sedek

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Divine love is ubiquitous in many religions and philosophies. In the Islamic Sufi tradition, it is recognized as an “intense yearning for unification” with God. Previous literature demonstrates that divine love plays a role in forming meaning and purpose in one’s life. However, previous research has not explored the effects of the Islamic practice of divine love contemplation on meaning and purpose in life. The current study used an experimental design to investigate whether a divine love contemplation intervention has an impact on meaning and purpose in life in Muslims through the framework of Islamic Psychology. The sample consisted of 34 participants (7 males and 27 females) who were randomly assigned to one of two groups: Intervention (n = 20) and Control (n = 14). Participants in the intervention group did a general litany and a divine love supplication and contemplation exercise, while participants in the control group did only a general litany exercise. Three hypotheses were tested using a mixed-design two-way (split-plot) Analysis of Variance (ANOVA) to determine whether participants in the intervention group will report a significant increase in 1) divine love, 2) meaning in life, and 3) purpose in life from before to after the intervention, whereas participants in the control group will not report a significant change in the mentioned constructs. The results supported Hypothesis 1, in that a significant interaction between group and time emerged for divine love. Specifically, the intervention group reported a significant increase in divine love from before to after the intervention, whereas the control group did not report a significant change in divine love. Furthermore, the effect size was large, even though the mean difference was negligible, indicating that this change was substantial enough to have a considerable effect on the sample. However, the tests of the second and third hypotheses were not significant, suggesting that the divine love contemplation intervention did not have a significant impact on meaning or purpose in life. Suggestions for future research include qualitative phenomenological studies that could be conducted to glean experiential insight into the constructs from the participants’ individual accounts.

Keywords: divine love, meaning in life, purpose in life, contemplation, islamic psychology

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Authors: Alireza Monzavi Chaleshtari, Mahnaz Aliakbari Dehkordi, Afsaneh Bayat, Amin Asadi Hieh

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The purpose of this research was to investigate the pattern of structural relationships of quality of life based on anxiety and rumination with the mediation of personality types in psoriasis patients. Methods: The community of this research is made up of the members of Psoriasis Society of Iran - Sadafak. In the sample size of 2266 people, according to Morgan's table, 327 people will be considered as a statistical sample. To assess the quality of life, the 26-item questionnaire of the World Health Organization, anxiety with software SPSS and appropriate to the conditions were used to test the hypotheses, correlation matrix tests and factor analysis. Results: There is a relationship between quality of life with anxiety and rumination in psoriasis patients. The mediating role of personality types showed Psychotic annoyance has a significant relationship with anxiety (physical and emotional symptoms). Extraversion, agreeing and being conscientious play a mediating role in a significant relationship between quality of life in psoriasis patients. Also, irritability plays a mediating role in a meaningful relationship between rumination in psoriasis patients. Conclusion: According to the obtained results, it can be said that psoriasis patients with physical and emotional symptoms of anxiety and rumination have a low quality of life. Also, negative personality types (perfectionism and neuroticism) can cause or aggravate skin disorders in these patients. In other words, psychological factors are considered predisposing, accelerating and perpetuating factors in psoriasis skin disorders, so it is suggested to pay attention to these variables in the success of treating patients with psoriasis.

Keywords: quality of life, anxiety, rumination, personality types, psoriasis.

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Authors: Khaled Alshamari

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Synthesized partially phosphorylated polyvinyl phosphate derivative (PPVP) was functionalized to extract Zirconium (IV) from Egyptian zircon sand. The specifications for the PPVP composite were approved effectively via different techniques, namely, FT-IR, XPS, BET, EDX, TGA, HNMR, C-NMR, GC-MS, XRD and ICP-OES analyses, which demonstrated a satisfactory synthesis of PPVP and zircon dissolution from Egyptian zircon sand. Factors controlling parameters, such as pH values, shaking time, initial zirconium concentration, PPVP dose, nitrate ions concentration, co-ions, temperature and eluting agents, have been optimized. At 25 ◦C, pH 0, 20 min shaking, 0.05 mol/L zirconium ions and 0.5 mol/L nitrate ions, PPVP has an exciting preservation potential of 195 mg/g, equivalent to 390 mg/L zirconium ions. From the extraction–distribution isotherm, the practical outcomes of Langmuir’s modeling are better than the Freundlich model, with a theoretical value of 196.07 mg/g, which is more in line with the experimental results of 195 mg/g. The zirconium ions adsorption onto the PPVP composite follows the pseudo-second-order kinetics with a theoretical capacity value of 204.08 mg/g. According to thermodynamic potential, the extraction process was expected to be an exothermic, spontaneous and beneficial extraction at low temperatures. The thermodynamic parameters ∆S (−0.03 kJ/mol), ∆H (−12.22 kJ/mol) and ∆G were also considered. As the temperature grows, ∆G values increase from −2.948 kJ/mol at 298 K to −1.941 kJ/mol at 338 K. Zirconium ions may be eluted from the working loaded PPVP by 0.025M HNO₃, with a 99% efficiency rate. It was found that zirconium ions revealed good separation factors towards some co-ions such as Hf⁴+ (28.82), Fe³+ (10.64), Ti⁴+ (28.82), V⁵+ (86.46) and U⁶+ (68.17). A successful alkali fusion technique with NaOH flux followed by the extraction with PPVP is used to obtain a high-purity zirconia concentrate with a zircon content of 72.77 % and a purity of 98.29%. As a result of this, the improved factors could finally be used.

Keywords: zirconium extraction, partially phosphorylated polyvinyl phosphate (PPVP), acidic medium, zircon

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Authors: Sahira N. Muslim, Alaa N. Mohammed, Saba Saadoon Khazaal, Batool Kadham Salman, Israa M. S. AL-Kadmy, Sraa N. Muslim, Ahmed S. Dwaish, Sawsan Mohammed Kareem, Sarah N. Aziz, Ruaa A. Jasim

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Tannase has wide applications in food, beverage, brewing, cosmetics and chemical industries and one of the major applications of tannase is the production of gallic acid. Gallic acid is used for manufacturing of trimethoprim. In the present study, a local fungal strain of Penicillium expansum A₄ isolated from spoilt apple samples gave the highest production level of tannase. Tannase was partially purified with a recovery yield of 92.52% and 6.32 fold of purification by precipitation using ammonium sulfate at 50% saturation. Tannase led to increased antimicrobial activity of ceftazidime against Pseudomonas aeruginosa and S. aureus and had a synergism effect at low concentrations of ceftazidime, and thus, tannase may be a useful adjuvant agent for the treatment of many bacterial infections in combination with ceftazidime.

Keywords: ceftazidime, Penicillium expansum, tannase, antimicrobial activity

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Authors: Fahed Alrshoudi

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Saudi Arabia is ranked the third of the largest suppliers of Dates worldwide (about 28.5 million palm trees), producing more than 2 million tons of dates yearly. These trees produce large quantity of dates palm seeds (DPS) which can be considered literally as a waste. The date seeds are stiff, therefore, it is possible to utilize DPS as coarse aggregates in lightweight concrete for certain structural applications and to participate at reusing the waste. The use of DPS as coarse aggregate in concrete can be an alternative choice as a partial replacement of the stone aggregates (SA). This paper reports the influence of partially replaced stone aggregates with DPS on the hardened properties of concrete performance. Based on the experimental results, the DPS has the potential use as an acceptable alternative aggregates in producing structural lightweight concrete members, instead of stone aggregates.

Keywords: compressive strength, tensile Strength, date palm seeds, aggregate

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Authors: Jihad S. Daba, J. P. Dubois

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Understanding the statistics of non-isotropic scattering multipath channels that fade randomly with respect to time, frequency, and space in a mobile environment is very crucial for the accurate detection of received signals in wireless and cellular communication systems. In this paper, we derive stochastic models for the probability density function (PDF) of the shift in the carrier frequency caused by the Doppler Effect on the received illuminating signal in the presence of a dominant line of sight. Our derivation is based on a generalized Clarke’s and a two-wave partially developed scattering models, where the statistical distribution of the frequency shift is shown to be consistent with the power spectral density of the Doppler shifted signal.

Keywords: Doppler shift, filtered Poisson process, generalized Clark’s model, non-isotropic scattering, partially developed scattering, Rician distribution

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Authors: Fiona Lourenco, William Allen

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Dentofacial deformities are primarily surgically treated via orthognathic surgery. Health-related quality of life is concerned with aspects of quality of life that relate specifically to an individual’s health. Design and Setting: Retrospective analysis of patients who had orthognathic surgery from January 2018 - December 2022 at the trust using the previously validated Orthognathic Quality of Life questionnaire (OQoL). Materials and Methods: 32 Patient questionnaires (which included pre-operative and post-operative separate sections) were obtained via telephone survey. The data was analysed using the two-tailed paired t-test and Wilcoxon signed-rank test. Results: The change in perception post-surgery was highly significant (both tests resulted in p<0.001 for overall analysis as well as for each domain). Overall, a 74% improvement in QoL was seen following orthognathic surgery. Reports of improvement in each domain were as follows: 71% in the social aspect of the deformity domain, 76% in facial aesthetics, 60% in function, and 57% improvement in awareness of facial deformity. Conclusion: The assessment of QoL is becoming progressively imperative in clinical research. The above data shows that orthognathic surgery has a significant improvement in the QoL of patients post-operatively. The results demonstrate improvement in all domains, with perceptions in facial aesthetics seeing the highest change post-operatively.

Keywords: dentofacial, oral, facial asymmetry, orthognathic surgery, quality of life

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Authors: Younes Abed

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The successful application of in-situ testing of soils heavily depends on development of interpretation methods of tests. The pressuremeter test simulates the expansion of a cylindrical cavity and because it has well defined boundary conditions, it is more unable to rigorous theoretical analysis (i. e. cavity expansion theory) then most other in-situ tests. In this article, and in order to make the identification process more convenient, we propose a relatively simple procedure which involves the numerical identification of some mechanical parameters of a granular soil, especially, the elastic modulus and the friction angle from a pressuremeter curve. The procedure, applied here to identify the parameters of generalised prager model associated to the Drucker & Prager criterion from a pressuremeter curve, is based on an inverse analysis approach, which consists of minimizing the function representing the difference between the experimental curve and the curve obtained by integrating the model along the loading path in in-situ testing. The numerical process implemented here is based on the established finite element program. We present a validation of the proposed approach by a database of tests on expansion of cylindrical cavity. This database consists of four types of tests; thick cylinder tests carried out on the Hostun RF sand, pressuremeter tests carried out on the Hostun sand, in-situ pressuremeter tests carried out at the site of Fos with marine self-boring pressuremeter and in-situ pressuremeter tests realized on the site of Labenne with Menard pressuremeter.

Keywords: granular soils, cavity expansion, pressuremeter test, finite element method, identification procedure

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Authors: Kamel Hachour, Lydia Sadeg, Djamel Sersab, Tassadit Bellahcen

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The hydrostatic stress is, for polymers, a significant parameter which affects the yield behavior of these materials. In this work, we investigate the influence of this parameter on yield behavior of the high density polyethylene (hdpe). Some tests on specimens with diverse geometries are described in this paper. Uniaxial tests: tensile on notched round bar specimens with different curvature radii, compression on cylindrical specimens and simple shear on parallelepiped specimens were performed. Biaxial tests with various combinations of tensile/compressive and shear loading on butterfly specimens were also realized in order to determine the hydrostatic stress for different states of solicitation. The experimental results show that the yield stress is very affected by the hydrostatic stress developed in the material during solicitations.

Keywords: biaxial tests, hdpe, Hydrostatic stress, yield behavior

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Authors: A. Mir, C. Aribi, B. Bezzazi

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Work presented is interested in the characterization of the quasistatic mechanical properties and in fatigue of a composite laminated in jute/epoxy. The natural fibers offer promising prospects thanks to their interesting specific properties, because of their low density, but also with their bio deterioration. Several scientific studies highlighted the good mechanical resistance of the vegetable fiber composites reinforced, even after several recycling. Because of the environmental standards which become increasingly severe, one attends the emergence of eco-materials at the base of natural fibers such as flax, bamboo, hemp, sisal, jute. The fatigue tests on elementary vegetable fibers show an increase of about 60% of the rigidity of elementary fibers of hemp subjected to cyclic loading. In this study, the test-tubes manufactured by the method infusion have sequences of stacking of 0/90° and ± 45° for the shearing and tensile tests. The quasistatic tests reveal a variability of the mechanical properties of about 8%. The tensile fatigue tests were carried out for levels of constraints equivalent to half of the ultimate values of the composite. Once the fatigue tests carried out for well-defined values of cycles, a series of static tests of traction type highlights the influence of the number of cycles on the quasi static mechanical behavior of the laminate jute/epoxy.

Keywords: jute, epoxy resin, mechanical, static, dynamic behavior

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Authors: Vatsal Patel, Niraj Shah

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This paper presents the results of a laboratory study on the properties of binary blended High Performance cementitious systems containing blends of ordinary Portland cement (OPC), Porcelain Powder or Marble Powder blend proportions of 100:00, 95:05, 90:10, 85:15, 80:20 for OPC: Porcelain Powder/Marble Powder. Studies on the Engineering Properties of the cementitious concrete, namely compressive strength, flexural strength, sorptivity, rapid chloride penetration test and accelerated corrosion test have been performed and those of OPC concrete. The results show that the inclusion of Porcelain powder or Marble Powder as binary blended cement alters to a great degree the properties of the binder as well as the resulting concrete. In addition, the results show that the Porcelain powder with 85:15 proportions and Marble powder with 90:10 proportions as binary systems to produce high-performance concrete could potentially be used in the concrete construction industry particular in lowering down the volume of OPC used and lowering emission of CO2 produces during manufacturing of cement.

Keywords: accelerated corrosion, binary blended cementitious system, rapid chloride penetration, sorptivity

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Authors: Kailash Ghimire, Manoj Thapa

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This study focuses on early identification of deficiencies in pre-required areas of students who are enrolled in College Algebra and Calculus I classes. The students were given pre-diagnostic tests on the first day of the class before they are provided with the syllabus. The tests consist of prerequisite, uniform and advanced content outlined by the University System of Georgia (USG). The results show that 48% of students in College Algebra are lacking prerequisite skills while 52% of Calculus I students are lacking prerequisite skills but, interestingly these students are prior exposed to uniform content and advanced content. The study is still in progress and this paper contains the outcome from Fall 2017 and Spring 2018. In this paper, early intervention used in these classes: two days vs three days meeting a week and students’ self-assessment using exam wrappers and their effectiveness on students’ learning will also be discussed. A result of this study shows that there is an improvement on Drop, Fail and Withdraw (DFW) rates by 7%-10% compared to those in previous semesters.

Keywords: student at risk, diagnostic tests, identification, intervention, normalization gain, validity of tests

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Authors: Shunpu Zhang

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We propose a new multiple test called the minPOP test for testing multiple hypotheses simultaneously. Under the assumption that the test statistics are independent, we show that the minPOP test has higher global power than the existing multiple testing methods. We further propose a stepwise multiple-testing procedure based on the minPOP test and two of its modified versions (the Double Truncated and Left Truncated minPOP tests). We show that these multiple tests have strong control of the family-wise error rate (FWER). A method for finding the p-values of the proposed tests after adjusting for multiplicity is also developed. Simulation results show that the Double Truncated and Left Truncated minPOP tests, in general, have a higher number of rejections than the existing multiple testing procedures.

Keywords: multiple test, single-step procedure, stepwise procedure, p-value for multiple testing

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Authors: Paul Han, Jun-Geol Baek

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In the flat panel display industry, the scheduler and dispatching system to meet production target quantities and the deadline of production are the major production management system which controls each facility production order and distribution of WIP (Work in Process). In dispatching system, delivery time is a key factor for the time when a lot can be supplied to the facility. In this paper, we use survival analysis methods to identify main factors and a forecasting model of delivery time. Of survival analysis techniques to select important explanatory variables, the cox proportional hazard model is used to. To make a prediction model, the Accelerated Failure Time (AFT) model was used. Performance comparisons were conducted with two other models, which are the technical statistics model based on transfer history and the linear regression model using same explanatory variables with AFT model. As a result, the Mean Square Error (MSE) criteria, the AFT model decreased by 33.8% compared to the existing prediction model, decreased by 5.3% compared to the linear regression model. This survival analysis approach is applicable to implementing a delivery time estimator in display manufacturing. And it can contribute to improve the productivity and reliability of production management system.

Keywords: delivery time, survival analysis, Cox PH model, accelerated failure time model

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Authors: Panwasn Mahalawalert

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The purposes of this research were analyzed differential item functioning and differential test functioning of SWUSAT aptitude test classification by sex variable. The data used in this research is the secondary data from Srinakharinwirot University Scholastic Aptitude Test 2013 (SWUSAT). SWUSAT test consists of four subjects. There are verbal ability test, number ability test, reasoning ability test and spatial ability test. The data analysis was analyzed in 2 steps. The first step was analyzing descriptive statistics. In the second step were analyzed differential item functioning (DIF) and differential test functioning (DTF) by using the DIFAS program. The research results were as follows: The results of DIF and DTF analysis for all 10 tests in year 2013. Gender was the characteristic that found DIF all 10 tests. The percentage of item number that found DIF is between 6.67% - 60%. There are 5 tests that most of items favors female group and 2 tests that most of items favors male group. There are 3 tests that the number of items favors female group equal favors male group. For Differential test functioning (DTF), there are 8 tests that have small level.

Keywords: aptitude test, differential item functioning, differential test functioning, educational measurement

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Authors: Hossein Heidari Tabrizi, Azizeh Chalak

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The present study investigated in depth the way translation teachers design and develop final tests as measures for checking on the quality of students’ academic translation in Iranian context. To achieve this goal, thirty experienced male and female translation teachers from the four types of the universities offering the program were invited to an in-depth 30-minute one-session semi-structured interview. The responses provided showed how much discrepancy exists among the Iranian translation teachers (as developers of final translation tests), who are least informed with the current translation evaluation methods. It was also revealed that the criteria they use for developing such tests and scoring student translations are not theory-driven but are highly subjective, mainly based on their personal experience and intuition. Hence, the quality and accountability of such tests are under serious question. The results also confirmed that the dominant method commonly and currently practiced is the purely essay-type format. To remedy the situation, some suggestions are in order. As part of the solution, to improve the reliability and validity of such tests, the present summative, product-oriented evaluation should be accompanied with some formative, process-oriented methods of evaluation. Training the teachers and helping them get acquainted with modern principles of translation evaluation as well as the existing models, and rating scales does improve the quality of academic translation evaluation.

Keywords: Iranian universities, students’ academic translations, translation final tests, undergraduate translation programs

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Authors: Ruangdech Sirikit

Abstract:

The purposes of this study were analyzed differential item functioning and differential test functioning of SWUSAT aptitude test classification by sex variable. The data used in this research is the secondary data from Srinakharinwirot University Scholastic Aptitude Test 2011 (SWUSAT 2011) SWUSAT test consists of four subjects. There are verbal ability test, number ability test, reasoning ability test and spatial ability test. The data analysis was carried out in 2 steps. The first step was analyzing descriptive statistics. In the second step were analyzed differential item functioning (DIF) and differential test functioning (DTF) by using the DIFAS program. The research results were as follows: The results of data analysis for all 10 tests in year 2011. Sex was the characteristic that found DIF all 10 tests. The percentage of item number that found DIF was between 10% - 46.67%. There are 4 tests that most of items favors female group. There are 3 tests that most of items favors male group and there are 3 tests that the number of items favors female group equal favors male group. For Differential test functioning (DTF), there are 8 tests that have small DIF effect variance.

Keywords: differential item functioning, differential test functioning, SWUSAT, aptitude test

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Authors: I. Ramirez D. Edgar, J. Angeles H. José, Ruiz C. Osvaldo, H. Jacobo A. Victor, Ortiz P. Armando

Abstract:

Knowledge of bone mechanical properties is important for bone substitutes design and fabrication, and more efficient prostheses development. The aim of this study is to characterize the viscoelastic behavior of bone specimens, through stress relaxation and fatigue tests performed to trabecular bone samples from bovine femoral heads. Relaxation tests consisted on preloading the samples at five different magnitudes and evaluate them for 1020 seconds, adjusting the results to a KWW mathematical model. Fatigue tests consisted of 700 load cycles and analyze their status at the end of the tests. As a conclusion we have that between relaxation stress and each preload there is linear relation and for samples with initial Young´s modulus greater than 1.5 GPa showed no effects due fatigue test loading cycles.

Keywords: bone viscoelasticity, fatigue test, stress relaxation test, trabecular bone properties

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Authors: Happy Zulu

Abstract:

Neuropsychological examination is an important way of formally assessing brain function. While there is so much documentation about the influence that some factors, such as age and education, have on neuropsychological tests (NP), not so much has been done to assess the influence that residency (rural/urban) may have. The specific objectives of this study were to establish if there is a significant difference in mean test scores on NP tests between rural and urban participants and to assess which tests on the Zambia Neurobehavioural Test Battery (ZNTB) are more affected by the participants‘ residency (rural/urban) and to determine the extent to which education, gender, and age predict test performance on NP tests for rural and urban participants. The participants (324) were drawn from both urban and rural areas of Zambia (Rural = 152 and Urban = 172). However, only 234 participants (Rural = 152 and Urban 82) were used for all the analyses in this particular study. The 234 participants were used as the actual proportion of the rural vs urban population in Zambia was 65% : 35%, respectively (CSO, 2003). The rural-urban ratio for the participants that were captured during the data collection process was 152 : 172, respectively. Thus, all the rural participants (152) were included and 90 of the 172 urban participants were randomly excluded so that the rural/urban ratio reached the desired 65% : 35 % which was the required ideal statistic for appropriate representation of the actual population in Zambia. Data on NP tests were analyzed from 234 participants, rural (N=152) reflecting 65% and urban (N=82) reflecting 35%. T-tests indicated that urban participants had superior performances in all the seven NP test domains, and all the mean differences in all these domains were found to be statistically significant. Residency had a large or moderate effect in five domains, while its effect size was small only in two of the domains. A standard multiple regression revealed that education, age and residency as predictor variables made a significant contribution to variance in performance on various domains of the ZNTB. However, the gender of participants was not a major factor in determining one‘s performance on neuropsychological tests. This particular report is part of an ongoing, larger, cutting-edge study aimed at formulating the normative data for Zambia with regard to performance on neuropsychological tests. This is necessary for appropriate, effective, and efficient assessment or diagnosis of various neurocognitive and neurobehavioural deficits that a number of people may currently be suffering from. It has been shown in this study that it is vital to make careful analyses of the variables that may be associated with one‘s performance on neuropsychological tests.

Keywords: neuropsychology, neurobehavioural, residency, Zambia

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Authors: Abdul Mufid

Abstract:

This study aims to integrate hadith, astronomy, and sociology studies in studying the accelerated implementation of the unification of the Hijri calendar through a multidisciplinary approach. The Hijri calendar is compiled based on the astronomical phenomena of regular movements of the earth, moon, and sun. Meanwhile, for the implementation of worship, the Hijri calendar must refer to the provisions of Islamic law or fiqh. To set the Hijri calendar, agreement on the criteria for the visibility of the new moon (first crescent), date limits, and absolute authority is required. Agreement on visibility criteria requires a valid basis for astronomical studies. Agreement on territorial boundaries is necessary because our earth is round, and the new moon cannot be observed simultaneously. And the agreement of the authorities is also needed to resolve unavoidable differences, especially differences in the appearance of the new moon and differences in schools of thought. The research is based on astronomical data, the experiences of Indonesia and Islamic countries regarding the Hijri calendar, in-depth and focused interviews with various sources, as well as a review of hadith literature. The results of the study show that the implementation of the unification of the Hijri calendar through the three approaches above can be carried out and can be accelerated.

Keywords: calendar unification, new moon (hilal) visibility, multidisciplinary approach, the unity of the Muslims

Procedia PDF Downloads 65