• Journal of the Korea Computer Industry Society
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• v.5 no.5
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• pp.721-728
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• 2004

OCSP (Online Certificate Status Protocol) server which checks the certificate status provides the real time status verification in the PKI (Public Key Infrastructure) system which is the essential system of certificate. However, OCSP server need the message authentication with the server and client, so it has some shortcomings that has slow response time for the demands of many clients concurrently and has complexity of the mathematical process in the public encryption system. In this research, simulation model of the certificate status vertification server is constructed of the DEVS (Discrete EVent system Specification) formalism. This sever model is constructed to practice the authentication with hash function when certificate is checked. Simulation results shows the results of increase of the certificate status verification speed and decrease of the response time to the client.

• Membrane and Water Treatment
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• v.7 no.2
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• pp.127-141
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• 2016

Electrodialysis (ED) is known to be a useful membrane process for desalination, concentration, separation, and purification in many fields. In this process, it is desirable to work at high current density in order to achieve fast desalination with the lowest possible effective membrane area. In practice, however, operating currents are restricted by the occurrence of concentration polarization phenomena. Many studies showed the occurrence of a limiting current density (LCD). The limiting current density in the electrodialysis process is an important parameter which determines the electrical resistance and the current utilization. Therefore, its reliable determination is required for designing an efficient electrodialysis plant. The purpose of this study is the development of a predictive model of the limiting current density in an electrodialysis process using response surface methodology (RSM). A two-factor central composite design (CCD) of RSM was used to analyze the effect of operation conditions (the initial salt concentration (C) and the linear flow velocity of solution to be treated (u)) on the limiting current density and to establish a regression model. All experiments were carried out on synthetic brackish water solutions using a laboratory scale electrodialysis cell. The limiting current density for each experiment was determined using the Cowan-Brown method. A suitable regression model for predicting LCD within the ranges of variables used was developed based on experimental results. The proposed mathematical quadratic model was simple. Its quality was evaluated by regression analysis and by the Analysis Of Variance, popularly known as the ANOVA.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.2
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• pp.667-674
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• 2015

Background: Colorectal cancer (CRC) is the third most common malignancy in Malaysia, where data are limited regarding knowledge and barriers in regard to CRC and screening tests. The aim of the study was to assess these parameters among Malaysians. Materials and Methods: The questionnaires were distributed in the Umra Private Hospital in Selangor. The questionnaire had four parts and covered social-demographic questions, respondent knowledge about CRC and colorectal tests, attitude towards CRC and respondentaction regarding CRC. More than half of Malay participants (total n=187) were female (57.2%) and 36.9% of them were working as professionals. Results: The majority of the participants (93.6%) never had a CRC screening test. The study found that only 10.2% of the study participants did not consider that their chances of getting CRC were high. A high percentage of the participants (43.3%) believed that they would have good chance of survival if the cancer would be found early. About one third of the respondents did not want to do screening because of fear of cancer, and concerns of embarrassment during the procedure adversely affected attitude to CRC screening as well. Age, gender, income, family history of CRC, vegetable intake and physical activity were found to be significant determinants of knowledge on CRC. Conclusions: The major barriers identified towards CRC screening identified in our study were fear of pain and embarrassment. The findings have implications for understanding of similarities and differences in attitude to CRC amongst elderly patients in other cultural/geographic regions.

• Education of Primary School Mathematics
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• v.20 no.2
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• pp.153-162
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• 2017

This study examined elementary pre-service teachers' (PSTs') perceived preparedness of high-leverage practices (HLPs) in mathematics teaching. Eighty-one elementary PSTs who enrolled in four sections of an elementary mathematics methods course at a Midwestern University in the United States participated in a survey that inquired their self-reported confidence and competence levels on HLPs. This study specifically investigated the comparison between PSTs' perceptions of HLPs and the mathematics teacher educators' expectations. Findings show several glaring differences between the PSTs' perceptions and experts' perceptions in regards to the complexity of some HLPs. This study suggests that initial teacher training programs should include more specific investment in PSTs' insights into details of each teaching practice in mathematics by deliberate decompositions.

• Journal of Educational Research in Mathematics
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• v.15 no.4
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• pp.489-504
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• 2005

In this paper, we design a environment in computers and mathematics education. For this purpose, we study two different points of view about relations between computers and mathematics education. As theoretical background, we also study constructionism and microworld. Next, we introduce functionization as a basic principle for computers and mathematics education. The concept of functionization focuses on the variation of mathematical objects, and it is a basic concept of both mathematics and computer science. We consider the concept of functionization as a paradigm for the research and practice of the computers and mathematics education. We also present the concept of functionization as a principle for designing a computer environment. Finally, we use the concept of functionization to integrate two famous microworlds, LOGO and DGS by introducing such objects as tiles and folding nets. Combining LOGO and DGS, we design a new microworld that can be used under the internet environment. We present tiles and folding nets to introduce how the concept of functionization is used to design a new microworld and to integrate two microworids.

• Steel and Composite Structures
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• v.22 no.4
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• pp.753-775
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• 2016

This paper aims to investigate the demountability of steel column-baseplate connections subjected to monotonic and cyclic loading. This paper presents the finite element analysis of steel column-baseplate connections under monotonic and cyclic loading. The finite element model takes into account the effects of material and geometric nonlinearities. Bauschinger and pinching effects were also included in the developed model, through which degradation of steel yield strength in cyclic loading can be well simulated. The results obtained from the finite element model are compared with the existing experimental results. It is demonstrated that the finite element model accurately predicts the initial stiffness, ultimate bending moment strength of steel column-baseplate connections. The finite element model is utilised to examine the effects of axial load, baseplate thickness, anchor bolt diameter and position on the behaviour of steel column-baseplate connections. The effects of various parameters on the demountability of steel column-baseplate connections are investigated. To achieve a demountable and reusable structure, various design parameters need to be considered. Initial stiffness and moment capacity of steel columnbaseplate connections are compared with design strengths from Eurocode 3. The comparison between finite element analysis and Eurocode 3 indicates that predictions of initial stiffness for semi-rigid connections should be developed and improved design of the connections needs to be used in engineering practice.

• Journal of Elementary Mathematics Education in Korea
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• v.20 no.3
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• pp.479-498
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• 2016

Time is important in children's lives since their preschool years. However, previous studies indicate that many children struggle with the acquisition of time concepts. Also teachers do not know how to help them. This study aims to investigate elementary school students' understanding about time and induce its educational implications. To do this, about 130 children from first to fifth grades were tested for their ability to recognize(read and record) the analogue and digital times and to solve elapsed-time problems. The results showed that even first graders were able to read and record the minute times on digital clocks. And second graders were able to read and record the minute times on analogue clocks. Therefore, the ability to recognize analogue times was mastered by second grade. In case of the elapsed-time problems, there was statistically significant difference according to school years or types of problems. Students were successful in solving simple problems. However, the problems that include regrouping hour and minute remained difficult even for the older children. Based on these results, we made a few suggestions for teaching practice about time.

• Education of Primary School Mathematics
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• v.13 no.1
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• pp.13-24
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• 2010

Mathematics educators oriented to reform-based curricular have asserted that mathematics teachers should lead instructions where all students in their classrooms are able to participated. In this paper, some practices for them to implement it are discussed. Before explaining them, some discussions are made about students ability to construct knowledge. One of them is that teachers should know different learners construct different understandings because of their differences of prior knowledge and reasoning ability. Also, it was discussed that teachers consider classroom environments, assigning children's sitting and tasks in the light of learning. The reason to state them is that perspectives of them should be changed. Finally, "Teacher's careful listening to learners' responses", "Why do think in that way?, How do you know?, What is it meant?", "accepting ideas from all learners", "no supporting a particular idea", "utilizing waiting time", and "teacher's responses to learner's errors and mistakes" are discussed as practices for letting all learners be participated in the mathematics instruction.

• Communications for Statistical Applications and Methods
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• v.25 no.3
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• pp.245-261
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• 2018

Attempts have been made to define new classes of distributions that provide more flexibility for modelling skewed data in practice. In this work we define a new extension of the generalized gamma distribution (Stacy, The Annals of Mathematical Statistics, 33, 1187-1192, 1962) for Marshall-Olkin generalized gamma (MOGG) distribution, based on the generator pioneered by Marshall and Olkin (Biometrika, 84, 641-652, 1997). This new lifetime model is very flexible including twenty one special models. The main advantage of the new family relies on the fact that practitioners will have a quite flexible distribution to fit real data from several fields, such as engineering, hydrology and survival analysis. Further, we also define a MOGG mixture model, a modification of the MOGG distribution for analyzing lifetime data in presence of cure fraction. This proposed model can be seen as a model of competing causes, where the parameter associated with the Marshall-Olkin distribution controls the activation mechanism of the latent risks (Cooner et al., Statistical Methods in Medical Research, 15, 307-324, 2006). The asymptotic properties of the maximum likelihood estimation approach of the parameters of the model are evaluated by means of simulation studies. The proposed distribution is fitted to two real data sets, one arising from measuring the strength of fibers and the other on melanoma data.

• Journal of Elementary Mathematics Education in Korea
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• v.17 no.1
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• pp.143-164
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• 2013

Despite the recent emphasis on mathematical communication, little practical guide has been provided for a teacher with what to do for orchestrating high-quality discussions in a mathematics classroom. This paper analyzed 20 elementary mathematics lessons which were recognized as effective instruction in Korea using an analytic framework with regard to 5 practices for orchestrating productive mathematics discussions (i.e., anticipating, monitoring, selecting, sequencing, & connecting) by Smith and Stein (2011) in terms of performance scales from Level 0 to 3. The results of this study showed that the most frequent levels were Level 1 including undesirable practices and Level 2 including insufficient practices. There were only one or two lessons per practice which were assessed as Level 3 of good performance. Specifically, Level 2 was the most frequent with regard to monitoring and selecting, whereas Level 1 was the most frequent as for the other practices. This paper provides some implications for co-ordinating productive mathematics discussions.