This study presents morphological and structural variations of K-Feldspar mineral after acid treatment. Both organic and inorganic acids such as C2H2O4, HCl, HNO3 and H2SO4 were employed for this ...purpose. Another aim of this study was to find an optimum experimental condition for iron (Fe) removal with a minimum damage on the structure of K-Feldspar in which high whiteness index is obtained. The effect of different parameters such as concentration, pH and temperature on the final structure of this mineral was investigated. To find out the chemical composition of powder, XRF was utilized. FTIR, XRD and SEM were employed to study the structure of mineral. Spectrophotometry was chosen to analyze whiteness index of powder after acid treatment. It was found that OAlO bond at 647 cm−1 for H2SO4 and HNO3 treated sample disappeared. However, HCl and C2H2O4 were ineffective at this band. In addition, the results revealed an increase in K-Feldspar content, a decrease in Fe content, an increase in whiteness index and no significant structural change for C2H2O4 leached sample. Whiteness index of 91% was obtained for C2H2O4 leached sample with the pH of 2.5 to 3 at temperature of 50 °C and during 1 h.
Display omitted
Considering that the use of thin-walled shells is expanding every day, it is important to examine the problem of instability in this form of structure. Many steel structures such as high-water tanks, ...water and oil reservoirs, marine structures, and pressure vessels, including shell elements, are under stress tension. In addition, shell elements are subject to instability owing to the loads applied. Ten thin-walled cylindrical shell specimens in two groups with different dent depths of t
c
and 2t
c
, and the different dent number subject to uniform external pressure were tested in the present research (t
c
is the thickness of cylindrical shell). The samples were modified to include either one or two dent line with amplitudes of h/3 in height (h the height of cylinder shell). Moreover, CFRP Strips on the dent depth was used in one of the groups. The results of testing under different theories and codes are compared.
PurposeThe purpose of this study is to measure the gap and compare the quality of services provided by the Central Library of the University of Tehran and Allameh Tabataba'i University and identify ...the components of service that need improvement in these libraries.Design/methodology/approachIn this study, a descriptive survey method is used for data collection. The study sample contains 205 people selected out of 31,000 members of Tehran University and 100 people out of 15,000 members at Allameh Tabataba'i University. The LibQual tool is used to measure different levels of users' perceptions of library service quality.FindingsBased on the findings of the study, the level of service received at the University of Tehran was higher than the minimum expected level, and at Allameh Tabataba'i University, the level of service received was lower than the minimum level of expected, which indicates users' satisfaction at this index at the University of Tehran and users' dissatisfaction at Allameh Tabataba'i University. In the index of information control and library as a place in Tehran University, the level of service received was higher than the minimum level and in Allameh Tabataba'i University, the level of service received was lower than the minimum level, which indicates the satisfaction of users in this index at the University of Tehran and users' dissatisfaction at Allameh Tabataba'i University.Practical implicationsService quality, or quality of service, is the measurement and comparison of the size of service provided with users' expectations. The following principles illustrate the dimensions of service quality: Quality of service is much more difficult to measure than the quality of goods. The quality of service is based on users' expectations. Quality of service varies in status, meaning that the quality of a service is measured against the customer's initial expectations of that service (Parasuraman et al., 1985).Originality/valueBeing the first performance evaluation, community synchronization, economic justification, user satisfaction and customer orientation are the values of the present study.
K‐Feldspar was used as a raw material for in situ synthesis of leucite particles by solid‐state reaction method. Prior to synthesis of leucite, K‐Feldspar was treated by oxalic acid (C2H2O4) to ...eliminate Fe content. The parameters affecting the structure and amount of Fe in K‐Feldspar was investigated to reach an optimal leaching condition. Next, kasilite removal was studied by introducing CaF2 to the composition of dental porcelain. To synthesis leucite, the prepared materials were heated up to 1450°C for 3 hours until fusion phenomena occurred, then cooled down to 865°C to permit the leucite crystals nucleate and grow. To find out the chemical composition of powder, XRF, EDX, and Atomic absorption spectroscopy were used. Fourier Transform Infrared Spectroscopy and X‐Ray Diffractometer and Scanning Electron Microscopy were employed to study the structure of mineral. Spectrophotometry was chosen to analyze whiteness index of powder after acid treatment. Differential Thermal Analysis was employed to determine the crystallization temperature. Results indicated a dramatic decrease in Fe content (0.018%wt) by employing C2H2O4 as a leachant at 50°C. In addition, whiteness index of 91% was achieved through this procedure for raw feldspar. Finally, 1%wt of CaF2 prevented formation of kalsilite.
Illustration of the preparation process for leucite‐based feldspathic dental porcelain before pigmentation.
Background and Aim: Hearing loss can have disabling effects on all aspects of children’s life and demographic factors of families can have significant effects on children’s auditory development. The ...main aim of the study was determining the effects of socioeconomic and education level on auditory behaviors of hearing-impaired children.
Methods: The study was cross sectional descriptive-analytic study and was conducted on 207 parents of children under age of four years with native Persian speaking parents with literacy skill. Their hearing impairment was identified before the first month of age. Early occurrence of hearing loss was considered to exclude any effects of early exposure to normal auditory stimuli on the outcome measurements. The children had at least 3-month experience with the cochlear implant (CI) after best fitting and adaptation to their device at the time of the study. Samples were selected by convenience sampling method from available subjects. For determining socioeconomic level, Ghodratnama socioeconomic status (SES) questionnaire was used. Infants and Toddlers Meaningful Auditory Integration Scale (IT-MAIS) was selected for the auditory behaviors study.
Results: Socioeconomic and educational level of the family showed no significant effects on auditory behaviors. The age of receiving auditory assistive device had weak but statistically significant effect on the outcome.
Conclusion: It seems that socioeconomic status and educational level of the family did not contribute to the auditory behaviors of children with cochlear implant. The generalizations of these results need further studies.
Keywords: Cochlear implant; pediatric; auditory behaviors; socioeconomic status
Metaverse can be considered as an example of emerging technologies that has major and diverse legal-economic challenges. A virtual network with a large and free environment in which many people use ...the form of avatars to communicate with each other in the fields of communication, work and business, property, playing games, They interact. Most of these challenges come back to the diverse functions of the metaverse. Functions such as education, entertainment, music, tourism, virtual ownership, virtual economy and jobs, cinema, artificial intelligence, etc. are among the activities of this virtual world. Issues that can be the basis of fundamental disputes in the social body and political and legal challenges of societies. Therefore, explaining the legal and economic challenges of the metaverse for political systems and citizens has made the present research inevitable. In this way, it is necessary to explain the exact nature of the metaverse, the legal challenges of its identification and the real and possible risks of this new technology, and to plan and propose innovative solutions to solve the challenges. Library and field studies are devoted to the analysis of the mentioned topics.
As moedas criptográficas se referem ao dinheiro eletrônico que é transferido digitalmente e não pode ser devolvido aos computadores através de uma plataforma chamada cadeia de bloqueio. Em outras ...palavras, o dinheiro virtual é criptografado com códigos eletrônicos e eles podem assim registrar transações; portanto, todas as moedas digitais, incluindo moedas bitcoin e de carteira podem ser um meio de pagamento para substituir o dinheiro físico para o fornecimento de bens e serviços, e podem ser usadas no lugar de moedas fiat em nível nacional e transnacional. Há várias vantagens para esta substituição, como a redução da produção de cédulas e moedas metálicas, mas este desenvolvimento na estrutura dos pagamentos monetários leva a desafios legais e políticos, e é necessário abordar esta questão na presente pesquisa. Como introdução, a igualdade das moedas fiat e spot deve ser medida e a possibilidade de aplicar os efeitos da moeda fiat à moeda spot e suas vantagens e desvantagens também deve ser analisada e explicada. Obviamente, analisar esta questão e generalizar as características do dinheiro físico ao virtual será eficaz e pioneiro para o comércio nacional e internacional, e identificar os desafios do unification pode fornecer uma plataforma adequada para a adoção de medidas preventivas em termos de eliminação e controle de possíveis riscos. Nesta base, a presente pesquisa analisou os tópicos através da coleta de dados e análise documental.
Metaverse can be considered as an example of emerging technologies that has major and diverse legal-economic challenges. A virtual network with a large and free environment in which many people use ...the form of avatars to communicate with each other in the fields of communication, work and business, property, playing games, They interact. Most of these challenges come back to the diverse functions of the metaverse. Functions such as education, entertainment, music, tourism, virtual ownership, virtual economy and jobs, cinema, artificial intelligence, etc. are among the activities of this virtual world. Issues that can be the basis of fundamental disputes in the social body and political and legal challenges of societies. Therefore, explaining the legal and economic challenges of the metaverse for political systems and citizens has made the present research inevitable. In this way, it is necessary to explain the exact nature of the metaverse, the legal challenges of its identification and the real and possible risks of this new technology, and to plan and propose innovative solutions to solve the challenges. Library and field studies are devoted to the analysis of the mentioned topics.
PDF
