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QRD-based Blind Detection for Orthogonal Space-Time Block Codes
Van-Su Pham,Minh-Tuan Le,Linh Mai,Jae-young Lee,S.M. Humayun Kabir,Giwan Yoon 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
This work presents a simplified QR decomposition based (QRD-based) blind decoding for Orthogonal Space-Time Block Codes (OSTBCs) with M-ary Phase Shift Keying (M-PSK) modulation constellation. By applying the proposed matrix partition, the blind detection problem becomes simpler. In addition, with the aid of QRD, the proposed detection requires a remarkably low complexity while maintaining a reasonable low Bit-error-rate (BER).
Fatigue behavior of an austenitic steel of 300-series under non-zero mean loading
S. M. Humayun Kabir,여태인 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.1
Strain-controlled fatigue data of an austenitic stainless steel subjected to uniaxial state at different strain ratios with tensile and compressive mean strain are experimentally investigated to understand the fatigue phenomena when non-zero mean straining is involved. The fatigue test result indicates that mean stresses relax to very low level and the material experiences elastic-plastic response throughout the life. Moreover, the material has higher fatigue resistance under tensile mean strain loading condition than that of completely reversed loading and compressive mean strain cycling at the same strain amplitude which might be attributed to the micro-structural deformation mechanism. The capabilities of several damage parameters to characterize the non-zero mean strain effect on fatigue life are examined based on fatigue data and are found inappropriate for the as-received material. Therefore, a fatigue damage approach with a power law relationship between modified damage parameter and reversals to failure, considering a mean strain function in stress-strain-based fatigue damage module, is introduced to the material which shows better correlation with the uniaxial fatigue data under mean strain loading compared to that of some established fatigue models.
Influence of temperature on a low-cycle fatigue behavior of a ferritic stainless steel
S. M. Humayun Kabir,여태인 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.7
The main objective of this study is to reveal the effect of dynamic strain ageing (DSA) on a ferritic stainless steel with detail relation tomonotonic and cyclic responses over a wide range of temperatures. For assessing the effect of strain rate on mechanical properties, tensiletest results are studied at two different strain rates of 2×10-3 /s and 2×10-4 /s. Typical responses of this material are compared with otheralloy in literatures that exhibits DSA. Serrations in monotonic stress-strain curves and anomalous dependence of tensile properties withtemperatures are attributed to the DSA effect. The low cycle fatigue curves exhibit prominent hardening and negative temperature dependenceof half-life plastic strain amplitude in temperatures between 300°C - 500°C which can be explained by DSA phenomenon. Theregime for dependence of marked cyclic hardening lies within the DSA regime of anomalous dependence of flow stress and dynamicstrain hardening stress with temperature and negative strain rate sensitivity regime of monotonic response. It is believed that shortenedfatigue life observed in the intermediate temperature is mainly due to the adverse effect of DSA. An empirical life prediction model isaddressed for as-received material to consider the effect of temperature on fatigue life. The numbers of load reversals obtained from experimentand predicted from fatigue parameter are compared and found to be in good agreement.
Evaluation of an energy-based fatigue approach considering mean stress effects
S. M. Humayun Kabir,여태인 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4
In this paper, an attempt is made to extend the total strain energy approach for predicting the fatigue life subjected to mean stress underuniaxial state. The effects of means stress on the fatigue failure of a ferritic stainless steel and high pressure tube steel are studied understrain-controlled low cycle fatigue condition. Based on the fatigue results from different strain ratios, modified total strain energy densityapproach is proposed to account for the mean stress effects. The proposed damage parameter provides convenient means of evaluatingfatigue life with mean stress effects considering the fact that the definitions used for measuring strain energies are the same as in thefully-reversed cycling (R = -1). A good agreement is observed between experimental life and predicted life using proposed approach. Two other mean stress models (Smith–Watson–Topper model and Morrow model) are also used to evaluate the low cycle fatigue data. Based on a simple statistical estimator, the proposed approach is compared with these models and is found realistic.
A Formula Derivation of Channel Capacity Calculation in a MIMO System
Kabir, S.M.Humayun,Lee, Eun-Ju,Yoon, Gi-Wan The Korea Institute of Information and Commucation 2009 Journal of information and communication convergen Vol.7 No.2
In this letter, we derive a tight closed-form formula for an ergodic capacity of a multiple-input multiple-output (MIMO) for the application of wireless communications. The derived expression is a simple closed-form formula to determine the ergodic capacity of MIMO systems. Assuming the channels are independent and identically distributed (i.i.d.) Rayleigh flat-fading between antenna pairs, the ergodic capacity can be expressed in a closed form as the finite sum of exponential integrals.
An Efficient Approach for Lightpath Restoration in WDM Networks
Kabir, S.M. Humayun,Pham, Van Su,Yoon, Gi-Wan The Korea Institute of Information and Commucation 2008 Journal of information and communication convergen Vol.6 No.1
WDM is an incredibly promising technique in which multiple channels are operated along a single fiber, providing the facilities of terabit per second bandwidth. Thus, the survivability of WDM networks becomes critical for the success of the next generation internet architecture. Despite the fact that the path-based proactive restoration scheme guarantees 100% restoration as it computes a backup light path while the primary light path is being set up, this method results in additional capacity consumption. In this paper, an ideal technique is proposed that modifies the active multi-backup paths method and results in a better restoration scheme. Based on a theoretical analysis, a new method is shown to reduce the number of hopes as well as the restoration time.
Derivation of Closed Form Channel Capacity Using Confluent Hypergeometric Function for Wireless MIMO
윤기완,Kabir, S.M.Humayun,Pham, Van-Su,Mai, Linh,Yoon, Gi-Wan 한국정보통신학회 2008 한국정보통신학회논문지 Vol.12 No.6
MIMO기술은 대역폭과 전력에 의해 제한을 받는 무선네트워크의 데이터 전송률을 증대시켜주는 효과적인 기술이다. 송수신단사이의 데이터 전송률은 채널용량에 의해 결정되며, MIMO기술은 이 채널용량을 적절히 이용함으로써 무선채널에서의 통신신뢰도를 높이는 이점을 가지고 있다. 본 논문은 Confluent Hypergeometric Function를 이용하여 새로운 공식 인 closed form capacity formula를 유도한다. Multiple-input multiple-output (MIMO) is an efficient technology to increase data rate in wireless networks due to bandwidth and power limitations. Data transmission rate between transmitter and receiver is determined by channel capacity. MIMO has an advantage of reliable communication over wireless channel because of utilizing the channel capacity properly. In this letter, we drive a new formula, closed form capacity formula, using confluent hypergeometric function.