• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.9
• /
• pp.1492-1512
• /
• 2011

Due to multiple hops, mobility and time-varying channel, supporting delay sensitive real-time traffic in wireless local area network-based (WLAN) mesh networks is a challenging task. In particular for real-time traffic subject to medium access control (MAC) layer control overhead, such as preamble, carrier sense waiting time and the random backoff period, the performance of real-time flows will be degraded greatly. In order to support real-time traffic, an efficient adaptive packet scheduling (APS) scheme is proposed, which aims to improve the system performance by guaranteeing inter-class, intra-class service differentiation and adaptively adjusting the packet length. APS classifies incoming packets by the IEEE 802.11e access class and then queued into a suitable buffer queue. APS employs strict priority service discipline for resource allocation among different service classes to achieve inter-class fairness. By estimating the received signal to interference plus noise ratio (SINR) per bit and current link condition, APS is able to calculate the optimized packet length with bi-dimensional markov MAC model to improve system performance. To achieve the fairness of intra-class, APS also takes maximum tolerable packet delay, transmission requests, and average allocation transmission into consideration to allocate transmission opportunity to the corresponding traffic. Detailed simulation results and comparison with IEEE 802.11e enhanced distributed channel access (EDCA) scheme show that the proposed APS scheme is able to effectively provide inter-class and intra-class differentiate services and improve QoS for real-time traffic in terms of throughput, end-to-end delay, packet loss rate and fairness.

• Journal for History of Mathematics
• /
• v.25 no.4
• /
• pp.139-155
• /
• 2012

This study researched the trends of mathematics education in Korean mathematics class in the aspects of teaching and learning method, assessment and teachers' competency based on TIMSS 1995, 1999, 2003 and 2007. For the mathematics teaching and learning method, the differentiated instruction rate is higher. The activities focused on students not teacher are more, and frequencies of homework are higher but time spent for homework is less than the past. Especially, mathematics teachers link homeworks to instructions. And mathematics teachers uses more multiple choice items and more various assessment methods than the past. The average age of mathematics teachers tends to become older since 1995. The major of mathematics teacher are primarily mathematics and mathematics education. Korean mathematics teachers have less self-esteem for teaching mathematics contents and have more various interactions with peers. The rate of participating in-service training is more or less according to training contents.

• Journal of KIISE:Computing Practices and Letters
• /
• v.6 no.1
• /
• pp.58-67
• /
• 2000

Todays enterprise networks are composed of multiple types of interconnected networks.Enterprise Networks interoperability between these technologies is needed. To enable interworking, it is necessary to be able to map between the relevant object models and to build on this to provide a mechanism to handle protocol conversion on the domain boundaries.In this paper, we describe a gateway between management application in the CORBA domain and agent in the SNMP domain and various integration methods. The main function of the gateway is to dynamically convert the method invocations on object reference in CORBA domain to SNMP messages for MIB entries at remote agents, We also present translation methods from SNMP MIB to CORBA IDL using Direct translation and Abstract translation. JIDM algorithm has no notion of containment and inheritance relationships between object classes and is difficult to understanding between management attribute and SNMP Action attribute. Abstract translation over come these problems.New superclasses define for common attributes and define explicit CORBA method for SNMP Action.It is a methodology for obtaining the CORBA-compliant management agents from already existing SNMP agents.

• Korean Journal of Remote Sensing
• /
• v.19 no.4
• /
• pp.329-339
• /
• 2003

In this study, an approach of image fusion in decision level has been proposed for unsupervised image classification using the images acquired from multiple sensors with different characteristics. The proposed method applies separately for each sensor the unsupervised image classification scheme based on spatial region growing segmentation, which makes use of hierarchical clustering, and computes iteratively the maximum likelihood estimates of fuzzy class vectors for the segmented regions by EM(expected maximization) algorithm. The fuzzy class vector is considered as an indicator vector whose elements represent the probabilities that the region belongs to the classes existed. Then, it combines the classification results of each sensor using the fuzzy class vectors. This approach does not require such a high precision in spatial coregistration between the images of different sensors as the image fusion scheme of pixel level does. In this study, the proposed method has been applied to multispectral SPOT and AIRSAR data observed over north-eastern area of Jeollabuk-do, and the experimental results show that it provides more correct information for the classification than the scheme using an augmented vector technique, which is the most conventional approach of image fusion in pixel level.

• Journal of the Korea Society of Computer and Information
• /
• v.6 no.4
• /
• pp.74-84
• /
• 2001

In the current Internet, InteServ model based on Resource reSerVation Protocol (RSVP), DiffServ Model based on service differentiation according to per hope behavior(PHB) and traffic engineering policy, and two-tire model of above mentioned two models which are adapted differently as the target network status for providing the end-to-end QoS Path are suggested. But, when we integrated this internet QoS into the ATM based network, differences of the connection setup procedure, name/address translation methods, and QoS provisioning mechanisms for end-to-end path setup procedures are introduced. In this paper, we propose the method of shortcut based QoS path setup procedure to solve these problems, and to guarantee the integration and scalability of Next Generation Internet(NGI) names/address in Integrated IP network into ATM based network. This network should support the engineering differentiated into the multiple service classes, which depend on established by this path is designed suitably into the target router and host step by step. In the near future, this function which provide the QoS guaranteed path based on end-to-end shortcut between the configuration devices are extended into the NGI target network.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.31 no.5
• /
• pp.987-999
• /
• 2021

Recently, Federated learning has become an issue due to privacy invasion caused by data. Federated learning is safe from privacy violations because it does not need to be collected into a server and does not require learning data. As a result, studies on application methods for utilizing distributed devices and data are underway. However, Federated learning is no longer safe as research on the reconstruction attack to restore learning data from gradients transmitted in the Federated learning process progresses. This paper is to verify numerically and visually how well data reconstruction attacks work in various data situations. Considering that the attacker does not know how the data is constructed, divide the data with the class from when only one data exists to when multiple data are distributed within the class, and use MNIST data as an evaluation index that is MSE, LOSS, PSNR, and SSIM. The fact is that the more classes and data, the higher MSE, LOSS, and PSNR and SSIM are, the lower the reconstruction performance, but sufficient privacy invasion is possible with several reconstructed images.

• Korean Journal of Remote Sensing
• /
• v.37 no.6_3
• /
• pp.2011-2025
• /
• 2021

In high-resolution satellite image classification, when the color values of pixels belonging to one class are different, such as buildings with various colors, it is difficult to determine the color information representing the class. In this paper, to solve the problem of determining the representative color information of a class, we propose a method to divide the color channel of HSV (Hue Saturation Value) and perform object-based classification. To this end, after transforming the input image of the RGB color space into the components of the HSV color space, the Hue component is divided into subchannels at regular intervals. The minimum distance-based image classification is performed for each hue subchannel, and the classification result is combined with the image segmentation result. As a result of applying the proposed method to KOMPSAT-3A imagery, the overall accuracy was 84.97% and the kappa coefficient was 77.56%, and the classification accuracy was improved by more than 10% compared to a commercial software.

• The Mathematical Education
• /
• v.58 no.3
• /
• pp.347-365
• /
• 2019

It is important to pay attention to how teachers recognize and use curriculum materials in order to link written curriculum and enacted curriculum. In this study, 90 preservice mathematics teachers were surveyed to identify their perspective and reading of curriculum materials. Especially, we focused on the curriculum documents, textbooks, and teachers' guidebooks containing the concept of conditional probability which is addressed in highschool mathematics curriculum. The various misconceptions of conditional probability were reported in the many researches, and there are multiple methods to introduce conditional probability in mathematics classes. As a result, curriculum materials have some limits to be used as they are and considered to be reconstructable by participants, but their curriculum reading were mainly classified to be descriptive and evaluative, not to be interpretive. However, unlike curriculum documents, textbooks and teachers' guidebooks were partially interpreted by participants using their knowledge of conditional probability. The purpose of this study is to investigate the profession of mathematics teachers in terms of curriculum implementation. We expect that this study will provide a basic framework for analyzing mathematics teachers' works and suggest some implications for the professional development of mathematics teachers.

• Journal of Science Education
• /
• v.42 no.3
• /
• pp.352-370
• /
• 2018

The purpose of this study is to explore how Peer Instruction can continuously help improve third-grade students' participation and their ability to debate in Science classes. There were multiple-choice questions relating to the discussions and debating class and Peer Instruction of the entire third grade Science curriculum which had been applied for six months. Also, after looking into the class participation and the debating ability, there was a degree of increase. As a result, there were five areas in class participation which are class preparation, class activity, expressing oneself, class expansion, and class dedication; all have statistically significant effects on the six areas of the discussion skill: logic, analytical skill, listening skill, receptiveness, regularity, and initiative. As it shows, both of these areas show a significant statistical effect on the application of Peer Instruction and confirmed to have a positive influence on the change in the participation and the discussion skills.

• Journal of the Korea Convergence Society
• /
• v.10 no.8
• /
• pp.283-289
• /
• 2019

The purpose of this study was to classify the elementary school students to latent groups according to the type of mobile phone usage and to verify the relationship with mobile phone dependency. The latent profile analysis was conducted using the first grade panel data of the elementary school in the Korea Children 's Youth Panel in 2016. The results found 3 latent classes of mobile phone usage: family and friend concentration (Type1), family concentration low level (Type2) and essential (Type3). The results of multiple regression analysis for verifying the relationship between mobile phone use type and mobile phone dependency showed a significant effect. The Type 2 showed more dependency than the Type 1, and the Type 1 showed more dependency than the Type 3. These findings provided basis for the guideline of mobile phones use and for proper intervention to prevent mobile phone dependency for elementary school students.