• Journal of the Korean Mathematical Society
• /
• v.35 no.2
• /
• pp.371-386
• /
• 1998

Let G be a compact Lie group and M a semialgebraic G space in some orthogonal representation space of G. We prove that if G is finite then M has an equivariant semialgebraic triangulation. Moreover this triangulation is unique. When G is not finite we show that M has a semialgebraic G CW complex structure, and this structure is unique. As a consequence compact semialgebraic G space has an equivariant simple homotopy type.

• Honam Mathematical Journal
• /
• v.39 no.1
• /
• pp.101-113
• /
• 2017

Let G be a semialgebraic group which is not necessarily compact. Let X be a proper semialgebraic G-set whose orbit space has a semialgebraic structure. In this paper we prove that X has a finite open straight G-CW complex structure.

• Bulletin of the Korean Mathematical Society
• /
• v.60 no.6
• /
• pp.1497-1522
• /
• 2023

In this paper we compute the Bredon homology of wallpaper groups with respect to the family of finite groups and with coefficients in the complex representation ring. We provide explicit bases of the homology groups in terms of irreducible characters of the stabilizers.

• Journal of the Korean Mathematical Society
• /
• v.49 no.2
• /
• pp.251-263
• /
• 2012

A CW complex B is said to be I-trivial if there does not exist a $\mathbb{Z}_2$-map from $S^{i-1}$ to S(${\alpha}$) for any vector bundle ${\alpha}$ over B a any integer i with i > dim ${\alpha}$. In this paper, we consider the question of determining whether $\Sigma^k\mathbb{R}P^n$ is I-trivial or not, and to this question we give complete answers when k $\neq$ 1, 3, 8 and partial answers when k = 1, 3, 8. A CW complex B is I-trivial if it is "W-trivial", that is, if for every vector bundle over B, all the Stiefel-Whitney classes vanish. We find, as a result, that $\Sigma^k\mathbb{R}P^n$ is a counterexample to the converse of th statement when k = 2, 4 or 8 and n $\geq$ 2k.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.16 no.1
• /
• pp.334-349
• /
• 2022

The effectiveness of Wi-Fi networks is greatly influenced by the optimization of contention window (CW) parameters. Unfortunately, the conventional approach employed by IEEE 802.11 wireless networks is not scalable enough to sustain consistent performance for the increasing number of stations. Yet, it is still the default when accessing channels for single-users of 802.11 transmissions. Recently, there has been a spike in attempts to enhance network performance using a machine learning (ML) technique known as reinforcement learning (RL). Its advantage is interacting with the surrounding environment and making decisions based on its own experience. Deep RL (DRL) uses deep neural networks (DNN) to deal with more complex environments (such as continuous state spaces or actions spaces) and to get optimum rewards. As a result, we present a new approach of CW control mechanism, which is termed as contention window threshold (CW_Threshold). It uses the DRL principle to define the threshold value and learn optimal settings under various network scenarios. We demonstrate our proposed method, known as a smart exponential-threshold-linear backoff algorithm with a deep Q-learning network (SETL-DQN). The simulation results show that our proposed SETL-DQN algorithm can effectively improve the throughput and reduce the collision rates.

• Journal of Advanced Navigation Technology
• /
• v.25 no.5
• /
• pp.426-432
• /
• 2021

Continuous wave (CW) Doppler radar has the advantage of being able to solve the privacy problem unlike camera and obtains signals in a non-contact manner. Therefore, this paper proposes a human activity recognition (HAR) system using CW Doppler radar, and presents the hardware design and implementation results for acceleration. CW Doppler radar measures signals for continuous operation of human. In order to obtain a single motion spectrogram from continuous signals, an algorithm for counting the number of movements is proposed. In addition, in order to minimize the computational complexity and memory usage, binarized neural network (BNN) was used to classify human motions, and the accuracy of 94% was shown. To accelerate the complex operations of BNN, the FPGA-based BNN accelerator was designed and implemented. The proposed HAR system was implemented using 7,673 logics, 12,105 registers, 10,211 combinational ALUTs, and 18.7 Kb of block memory. As a result of performance evaluation, the operation speed was improved by 99.97% compared to the software implementation.

• Proceedings of the Korea Society for Simulation Conference
• /
• 1999.04a
• /
• pp.26-31
• /
• 1999

As a part of work to simulate electromagnetic environments for Hareware-In-the-Loop Simulation, clutter signals of pulsed dopplar radar(altimeter) and CW radar are modeled as numerical expressions for various parameters. The simulated results show that this method is applicable to simulate complex electromagnetic environments.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.8 no.10
• /
• pp.3458-3474
• /
• 2014

The performance of IEEE 802.11e enhanced distributed channel access (EDCA) is influenced by several interactive parameters that make quality of service (QoS) control complex and difficult. In EDCA, the most critical performance influencing parameters are the arbitration interframe space (AIFS) and contention window size (CW) of each access category (AC). The objective of this paper is to provide a scheme for parameter control such that the throughput per station as well as the overall system throughput of the network is maximized and controllable. For this purpose, a simple and accurate analytical model describing the throughput behavior of EDCA networks is presented in this paper. Based on this model, the paper further provides a scheme in which a Pareto optimal system configuration is obtained via an appropriate CW control for a given AIFS value, which is a different approach compared to relevant papers in the literature that deal with CW control only. The simulation results confirm the effectiveness of the proposed method which shows significant performance improvements compared to other existing algorithms.

• The Journal of the Korean Society for Microbiology
• /
• v.21 no.2
• /
• pp.233-241
• /
• 1986

Patients of chronic hepatic diseases(n=107) including chronic hepatitis caused by hepatitis B virus infections(n=31), liver cirrhosis(n=53), and hepatocellular carcinoma(n=23) were examined to ascertain genetic relationship between chronic hepatic diseases and histocompatibility antigen. Peripheral blood lymphocytes were separated from whole blood by the method of Ficoll/Hypaque gradient. Total 54 histocompatibility antigens(class I antigens: 41, class II antigens: 13) were analysed by performing of complement dependent microlymphocytotoxicity method using Terasaki's and Catholic Medical College tissue typing plates. HLA antigen frequencies were compared with those of 661 normal controls. The following results were obtained: 1. HLA antigen frequencies of HLA-Bw46, -Bw76, -Cw1, -Cw6, and HLA-DR8 in chronic hepatitis patients were shown to be higher than those in controls(P<0.01). 2. HLA antigen frequencies of HLA-Bw46, -Cw7(P<0.01), and HLA-B37, -Bw58, -Cw1, -MT1(P < 0.05) in liver cirrhosis patients were shown relatively higher frequencies than those in controls. 3. In patients with hepatocellular carcinoma, antigens of HLA-A1, -A26, -Cw3, -Cw7 and HLA-DR6 were dominantly detected. 4. There were negative associations with HLA-Cw4, and -DR4 in patients of chronic hepatic diseases(P < 0.05).

• Bulletin of the Korean Mathematical Society
• /
• v.41 no.3
• /
• pp.393-401
• /
• 2004

In this paper, we apply the concept of the group \ulcorner(X,A) of self pair homotopy equivalences of a CW-pair (X, A) to the Postnikov system. By using a short exact sequence related to the group of self pair homotopy equivalences, we obtain the following result: for any Postnikov section X$\sub$n/ of a CW-complex X, the group \ulcorner(X$\sub$n/, A) of self pair homotopy equivalences on the pair (X$\sub$n/, X) is isomorphic to the group \ulcorner(X) of self homotopy equivalences on X. As a corollary, we have, \ulcorner(K($\pi$, n), M($\pi$, n)) ≡ \ulcorner(M($\pi$, n)) for each n$\pi$1, where K($\pi$,n) is an Eilenberg-Mclane space and M($\pi$,n) is a Moore space.