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Signal Processing of WiMAX Physical Layer Based on Low-Density Parity-Check Codes
Chawalit Benjangkaprasert,Torpong Inchan 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10
WiMAX technology supports very high data rate, high capacity and high quality in mobile broadband wireless access system. The performance of the WiMAX system can be enhanced by incorporating a better channel coding technique. This paper presents the excellent performance channel coding known as low-density parity check (LDPC) codes which is a part of WiMAX system. A modified array code parity check matrix for LDPC encoder is used and the message passing (MP) algorithm for LDPC decoder is used, respectively. Both systems are modulated by the basic standard modulation scheme. The computer simulation results confirm that the bit error rate (BER) performance of the WiMAX system that incorporate with the powerful LDPC coding technique has been improved over the conventional standard WiMAX system. However, the computational complexity of the proposed WiMAX system is higher than the previous one.
Robust PID Controller Design Using Convex-Concave Optimization
Chawalit Thabthimrattana,Surachai Saelim,Suchol Tiewcharoen,Sudchai Boonto 제어로봇시스템학회 2016 제어로봇시스템학회 국제학술대회 논문집 Vol.2016 No.10
This paper shows a PI with phase-lead controller design using convex-concave optimization. The phase-lead term is added to reduce a high frequency measurement noise effect. By fixing all parameters of the phase-lead part, the optimization program searches the remain parameters subject to robustness constraints. The optimization constraints are functions in a frequency domain. The design problem can be solved by frequency gridding on a software package CVX. Experiments on an unstable magnetic levitation system are presented. The proposed controller shows significantly better performance than a robust H∞ controller designed by a standard method on the same unstable system.
Hybrid Simulation Model for the Upstream Rubber Supply Chain
Chawalit Manisri,Juta Pichitlamken 대한산업공학회 2017 Industrial Engineeering & Management Systems Vol.16 No.3
Thailand has been one of the largest natural rubber (NR) exporters in the world since 1991. However, the upstream rubber supply chain suffers from problems such as oversupply and decreasing price. This work proposed a decisionsupport model that combines System Dynamics and Agent-Based Modeling simulation while taking into account the relationship between NR price and planting rate per year, as well as between NR price and crude oil price. The input data between 2002 and 2015 included area sizes, tapping yield, planting rates, growth rates, and time to start or end tapping. The upstream rubber supply chain models were simulated from 2002 to 2021. The hybrid models in this study were validated by comparing between the simulated NR volume and actual values. The average Mean Absolute Percentage Error was 8.6%. The results of this work may be used by stakeholders in NR supply chains, such as in government agencies, to support their policy making.
Chawalit Lertbutsayanukul,Manida Pitak,Chonnipa Nantavithya 대한방사선종양학회 2022 Radiation Oncology Journal Vol.40 No.2
Purpose: For patients with early breast cancer who undergo breast-conserving surgery, adjuvant whole breast irradiation (WBI) with simultaneous integrated boost (SIB) results in lower radiotherapy fractions. Published studies have shown that both conventional fraction with SIB (C-SIB) and hypofractionation with SIB (H-SIB) seem to be safe and feasible. In this study, we sought to compare the oncologic outcomes between C-SIB and H-SIB in early-stage breast cancer. Materials and Methods: Stage I-II breast cancer patients who received adjuvant WBI with SIB between January 2008 and December 2017 were retrospectively reviewed. The radiation dose in the C-SIB group was 50 Gy and 65 Gy in 25 daily fractions, while in the H-SIB group, it was 43.2 Gy and 52.8 Gy in 16 daily fractions to the whole breast and tumor bed, respectively. Results: A total of 188 patients, 103 in the C-SIB group and 85 in the H-SIB group, were included. With a median follow-up time of 87 months, 7-year locoregional control of C-SIB was comparable to H-SIB (95.8% vs. 97.4%, p = 0.964). The 7-year distant metastasis-free survival rates of C-SIB and H-SIB were 89.9% and 95.9% (p = 0.111), while the 7-year disease-free survival rates were 84.2% and 95.4%, respectively (p = 0.176). In multivariate analysis, there was no significant prognostic factor associated with better overall survival. Conclusion: H-SIB provided comparable locoregional control to C-SIB. With the advantage of a shorter radiotherapy course, H-SIB could be a favorable option for WBI in early-stage breast cancer.
Chawalit Jeenanunta,Nattharika Rittippant,Pornpimol Chongphaisal,Ryoju Hamada,Nuchjarin Intalar,Kimseng Tieng,Kwanchanok Chumnumporn 기술경영경제학회 2017 ASIAN JOURNAL OF TECHNOLOGY INNOVATION Vol.25 No.2
The objective of this paper is to investigate the human resourcemanagement (HRM) and coordination activities for innovation inproduction network. We consider three manufacturing firms inthis study, Global Green Chemicals Public Company Limited,Thaioil Public Company Limited and Siam Cement GroupChemicals Company Limited. In each case, the key innovationmilestones are identified. We also examine how HRM and humanresource development (HRD) are utilized to improve innovationand technological capabilities. From our results, we conclude thattop management plays an important role in HRM/HRD to improvea firm’s innovation and technological capabilities. Systematicrecruitment, selection, training and development are needed toachieve organizational strategies. Career path development and areward system are important motivators for employee retention.
Chawalit Ngamcharussrivichai,Warakorn Meechan,Anawat Ketcong,Kunn Kangwansaichon,Suchada Butnark 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.3
A limestone from the South of Thailand was utilized as a source for preparation of heterogeneous base catalysts for transesterification of various vegetable oils with methanol and ethanol has been investigated. Series of CMA catalysts were prepared through a wet mixing of ground limestone with different divalent and trivalent metal precursors, as binders, followed by drying and calcination. Effects of preparation conditions, including types of wetting media and metal precursors, metal compositions,and thermal treatment temperatures for the parent limestone and the mixed catalyst precursors, on the structural properties and the transesterification activity of the resultant catalysts, and on the catalyst formulation were studied. The catalytic test under batch conditions at 60 8C indicated an enhancement of the methyl ester formation over the catalysts prepared due to the presence of new active phase generated in situ upon the calcination of the mixed catalyst precursors at high temperatures. The metal precursors also acted as good binders in the catalyst shaping. Using the sodium salt of Al as a precursor remarkably improved the mechanical strength of the catalyst extrudates. The CMA catalysts can be regenerated and reused without a severe drop of the methyl ester yield. Moreover, the transesterification in a continuous-flow fixed bed reactor indicated a good activity and stability of the catalyst extrudates prepared.
Generalized $(\Lambda,b)$-closed sets in topological spaces
Chawalit Boonpok 강원경기수학회 2017 한국수학논문집 Vol.25 No.3
A new class of sets, called generalized $(\Lambda,b)$-closed sets, has been introduced and studied. Also, several properties of generalized $(\Lambda,b)$-closed sets are investigated. Some characterizations of $\Lambda_b$-regular spaces and $\Lambda_b$-normal spaces are discussed.