Papers by Mohammad Rezaeian
International Journal of Livestock Research, 2016
Ten accessions of Napier grass were evaluated for their chemical composition and in-vitro organic... more Ten accessions of Napier grass were evaluated for their chemical composition and in-vitro organic matter digestibility at Holetta and Areka environmental conditions during 2014 cropping season. The study was conducted in randomized complete block design with three replications. Data on nutritional qualities were analyzed using the general linear model procedures of SAS and least significance difference was used for mean comparisons. The result showed that Napier grass accessions respond differently for chemical composition and in-vitro organic matter digestibility at both testing environments. The chemical compositions and in-vitro organic matter digestibility indicated that the mean ash, CP, IVOMD, ADF, and cellulose contents were comparatively higher at Holetta than Areka conditions. On the other hand, the mean CP yield, digestible yield, NDF, ADL and hemicellulose contents were higher at Areka than Holetta. The CP and IVOMD were higher in the highland while CP yield, digestible yield and most fiber components were relatively higher in the mid altitude area indicating that temperature and amount of rainfall and distribution had an adverse effect on the feed quality of Napier grass.
Anaerobe, 2005
The fibrolytic activities of rumen fungi were studied in terms of dry matter loss, plant cell wal... more The fibrolytic activities of rumen fungi were studied in terms of dry matter loss, plant cell wall degradation and enzyme (cellulase and xylanase) activities, when grown in vitro on either untreated or sodium hydroxide treated stems of barley straw over a 12 day period. Changes in fungal growth, development and overall biomass were followed using chitin assay and scanning electron microscopy. Treatment with sodium hydroxide resulted in a decrease in the NDF content together with the disruption of cuticle and the loosening and separation of the plant cells within the straw fragments. The enzyme activities of the anaerobic fungi have a high positive correlation (R(2)=0.99) with their biomass concentration assessed by chitin assay indicating that chitin is a valuable index for the estimation of the fungal biomass in vitro. The anaerobic fungi produced very extensive rhizoidal systems in these in vitro cultures. After incubation with rumen fungi, dry matter losses were, respectively, 35...
Using concepts from coding theory, we define eachievability for target tracking in binary sensor ... more Using concepts from coding theory, we define eachievability for target tracking in binary sensor networks and compare this to the more usual notion of trackability: a target can be tracked in a binary sensor network through a query mechanism if the tracker obtains the correct target track history at infinitely many times almost surely. Trackability is a relatively weak conclusion, allowing the possibility that at most times the track history estimate will be incorrect with high probability. The stronger condition of e-achievability requires the existence of a query strategy that ensures that the probability of error in estimating the track history converges exponentially to zero over time with exponent e. We provide necessary and sufficient conditions on the query rate of the network for e-achievability by extending the concept of e-achievability from that for fixed length codes to weak variable length codes. These conditions are related to the Renyi entropy rate of the target, and has similarities with results on fixed length source coding, though the derivation of our sufficient condition is based entirely on large deviation theory.
Numerical solutions to the Bloch-McConnell equations with radio frequency irradiation scheme for CEST MRI
20th Iranian Conference on Electrical Engineering (ICEE2012), 2012
ABSTRACT
We consider a pair of correlated processes in {Zn}n=-infin infin and {Zn}n=-infin infin, where th... more We consider a pair of correlated processes in {Zn}n=-infin infin and {Zn}n=-infin infin, where the former is observable and the latter is hidden. The uncertainty in the estimation of Sn upon the finite past history of Z0 n-infin1 is H(Sn|)Z0 ninfin1 which is a sequence of n. The limit of Cesaro mean of this sequence is called the estimation entropy.
2010 13th International Conference on Information Fusion, 2010
Hierarchial radar resource management uses multi object Markov decision scheduling with a constra... more Hierarchial radar resource management uses multi object Markov decision scheduling with a constraint on the resources. In this paper we give a detailed description of constrained multi-object Markov decision scheduling in its general form and the separation that is achieved in the dynamic programming level using Lagrange multipliers. We then apply this general model to obtain a simultaneous beam and waveform scheduling method for radars based on an objective function that depends on both state and action. This method extends on a previous hierarchial method for beam scheduling with an objective function defined only on state. We further improve the objective function based on entropy reduction. This criterion makes the resource management to be more flexible in favor of measurements that carry more information.
2005 7th International Conference on Information Fusion, 2005
Modern phased array radars, with flexible waveform generation and beam steering capability, are a... more Modern phased array radars, with flexible waveform generation and beam steering capability, are able to adaptively modify their performance to suit a variety of environments. This power has not yet been fully exploited, in part because of the lack of suitable scheduling algorithms. This paper describes an optimal adaptive waveform selection algorithm for target tracking. An adaptive scheduling algorithm that selects the waveforms to be used in future epochs based on current estimates of the environment has the potential to significantly improve tracking performance. This paper describes such a scheduling algorithm, which is designed by posing the problem of adaptive waveform scheduling for target tracking as a stochastic dynamic programming problem. The result is a scheduling algorithm that minimises target tracking errors. The performance of the algorithm is illustrated by comparing the tracking errors produced by this approach in comparison to a fixed waveform schedule.
2013 20th Iranian Conference on Biomedical Engineering (ICBME), 2013
Chemical exchange saturation transfer (CEST) is a new mechanism of contrast generation in magneti... more Chemical exchange saturation transfer (CEST) is a new mechanism of contrast generation in magnetic resonance imaging (MRI) which differentiates molecule biomarkers via chemical shift. CEST MRI contrast mechanism is very complex and depends on radio frequency (RF) power and RF pulse shape. Two approaches have been used to saturate contrast agent (CA) protons: continuous wave CEST (CW-CEST) and pulsed CEST. To find the optimal RF pulse, numerical solution of Bloch-McConnell equations (BME) may be used. In this paperwe find the optimum values of RF pulse parameters that maximize the CEST contrast. Discrete pulses have lower specific absorption ratio (SAR) than CW RF pulses. However, since discretization is performed on continuous RF pulses, optimizing the continuous RF pulses leads to the optimization of discrete RF pulses. Therefore, in this paper, Rectangular, Gaussian and Fermi pulses are investigated as CW RF pulses. In this investigation, in addition to considering the SAR limitation, 60 dB approximation for the RF pulse amplitude is used. To compare the efficiency of pulses, their resultant flip angles (FA) are assumed equal. Efficiency of CW-CEST is investigated using two parameters, CEST ratio and SAR. According to these parametres, rectangular, Fermi and Gaussian RF pulses have the best performance respectively. Since implementation of rectangular RF is harder than Gaussian and Fermi RF pulses, Fermi and Gaussian RF pulses are desired. Our results suggest that it is possible to maximize CEST ratio by optimizing parameters of rectangular (with an amplitude of 5.7µT), Gaussian (σ about 0.7s) and Fermi (a-value about 0.3s) pulses. Results are verified by empirical formulation of CEST ratio.
Fifth Annual IEEE International Conference on Pervasive Computing and Communications Workshops (PerComW'07), 2007
We consider sensor scheduling as the optimal observability problem for partially observable Marko... more We consider sensor scheduling as the optimal observability problem for partially observable Markov decision processes (POMDP). This model fits to the cases where a Markov process is observed by a single sensor which needs to be dynamically adjusted or by a set of sensors which are selected one at a time in a way that maximizes the information acquisition from the process. Similar to conventional POMDP problems, in this model the control action is based on all past measurements; however here this action is not for the control of state process, which is autonomous, but it is for influencing the measurement of that process. This POMDP is a controlled version of the hidden Markov process, and we show that its optimal observability problem can be formulated as an average cost Markov decision process (MDP) scheduling problem. In this problem, a policy is a rule for selecting sensors or adjusting the measuring device based on the measurement history. Given a policy, we can evaluate the estimation entropy for the joint state-measurement processes which inversely measures the observability of state process for that policy. Considering estimation entropy as the cost of a policy, we show that the problem of finding optimal policy is equivalent to an average cost MDP scheduling problem where the cost function is the entropy function over the belief space. This allows the application of the policy iteration algorithm for finding the policy achieving minimum estimation entropy, thus optimum observability.
IEEE International Symposium on Information Theory, 2003. Proceedings., 2003
We introduce a simple on-off fading discrete memoryless multiple-access channel model. The multip... more We introduce a simple on-off fading discrete memoryless multiple-access channel model. The multiplicative fading for each user is modelled as a bernoulli random process, in which each symbol is multiplied by a random channel gain that is either zero or one. We find the capacity of this channel in the case that the receiver does not know the values of the channel gains. Index Terms-multiple-access channel, interference channel, fading channels I. INTRODUCTION Fading channels are a common model for wireless communications. By fading, we generally mean that signals transmitted over the channel are disturbed by a multiplicative noise process, in addition to the usual additive noise. The capacity for fading channels, in the case that neither the transmitter or the receiver knows value of the fading realization is largely an open problem. For single user Rayleigh fading channels, it has been shown that the capacity achieving distribution is discrete [1], and numerical methods must be used to find capacity. Multiple-input, multiple output Rayleigh fading channels with no channel state information have been considered in [2, 3] (systems with channel state information were considered in [4, 5]). Although the form of the capacity achieving distribution is known, apart from some special and limiting cases, determination of the capacity is an open problem for such channel. Further results for this channel may be found in [6]. Fading multiple-access channels have been considered in [7], but once again, only partial results have been obtained. In particular, they show that if the fading coefficients take on new independent values for every symbol then the total capacity for M > 1 users is equal to the capacity for M = 1 user, implying that time division multiple access is an optimal strategy. Rather than attempt to extend the results for Rayleigh fading channels, we shall consider a very simple model for M-user fading multiple-access channels in which each symbol of each user's transmission is either faded (multiplied by zero), or not faded (multiplied by one). By considering such a simple channel model, we hope to gain some insight into the effects of fading on multiple-user channels. This channel also provides a very crude approximation to more realistic fading channels and therefore may be interesting in its own right. Definition 1 (On-Off Fading Channel). An on-off fading multiple-access channel is an M-user discrete memoryless
Improvements to random accessing using multiuser detection
International Zurich Seminar on Communications, 2004
We extend Massey and Mathys' collision channel without feedback by introducing a probability... more We extend Massey and Mathys' collision channel without feedback by introducing a probability of recovery from collision. As the main result we derive the slot-synchronized capacity region of this recovery channel. We also explore the effect of a simple fading model.
International Symposium onInformation Theory, 2004. ISIT 2004. Proceedings.
IEEE Transactions on Signal Processing, 2010
This paper considers the performance limits for joint detection and estimation from a finite setv... more This paper considers the performance limits for joint detection and estimation from a finite setvalued observation that is stochastically related to the state or parameter of interest. Detection refers to inference about the existence of the state, whereas estimation refers to inference about its value, when detected. Since we need to determine the existence/non-existence of the state as well as its value, the usual notion of Euclidean distance error does not jointly capture detection and estimation error in a meaningful manner. Treating the state as set, which can be either empty or singleton, admits a meaningful distance error for joint detection and estimation. We derive bounds on this distance error for a widely used class of observation models. When existence of the state is a certainty, our bounds coincide with recent results on Cramér-Rao bounds for estimation only problems.
IEEE Transactions on Information Theory, 2005
We consider a simple conceptual model of random accessing to a receiver deploying multiuser detec... more We consider a simple conceptual model of random accessing to a receiver deploying multiuser detection techniques. The model is a simple extension of Massey and Mathys' collision channel without feedback in which a certain probability of recovery from collision is introduced. As the main result, we derive the slot-synchronized capacity region of this recovery channel and show that for sufficiently powerful multiuser detectors, maximal performance is achieved without any sophisticated transmission protocols. We also explore the effect of a simple fading model.
IEEE Transactions on Information Theory, 2004
The Arimoto-Blahut algorithm is generalized for computation of the total capacity of discrete mem... more The Arimoto-Blahut algorithm is generalized for computation of the total capacity of discrete memoryless multiple-access channels (MACs). In addition, a class of MACs is defined with the property that the uniform distribution achieves the total capacity. These results are based on the specialization of the Kuhn-Tucker condition for the total capacity of the MAC, and an extension of a known symmetry property for single-user channels. Index Terms-Arimoto-Blahut algorithm, capacity, multiple-access channel (MAC), nonconvex optimization. I. INTRODUCTION Determination of the capacity region for multiterminal channels has attracted much attention in information theory. In many cases, single-letter representations of the capacity region are not known. Even in cases where a single-letter description has been found, such as the discrete memoryless multiple-access channel (MAC), evaluation of the capacity region is problematic. Specifically, computation of the boundary of the capacity region is a nonconvex optimization problem. In contrast, for single-user channels in case of symmetry the capacity-achieving distribution is known, and in other cases, channel capacity can be numerically approximated to arbitrary precision using the Arimoto-Blahut algorithm [1]-[3] or other numerical optimization procedures [4], [5]. Such techniques are still lacking for the MAC in its general form. A numerical method has been developed for two-user MACs with binary output [6]. Of particular interest for this correspondence is the computation of the total capacity, C total for the discrete memoryless MAC. This is the solution of the following optimization problem: max P (X)P (X)...P (X) I (X1; X2;. .. ; XM ; Y): (1) The problem of capacity computation for a single-user channel is convex, and therefore the Kuhn-Tucker condition [7] is sufficient for a distribution to achieve capacity. For a MAC, this convexity is missing. Nevertheless, recent results [8] have shown that the Kuhn-Tucker condition is either sufficient for optimality in a MAC, or the channel can be decomposed into subchannels for which the Kuhn-Tucker condition is sufficient for optimality. In the latter case, at least one subchannel has an optimal distribution that achieves the capacity of the original channel. In light of the result reported in [8], this correspondence gives capacity computation methods for the MAC analogous to the methods used for single-user channels. Starting with an information function defined in Section II, a specialization of the Kuhn-Tucker condition for the maximization (1) is given in Section III. This allows the derivation
IEEE Transactions on Automatic Control, 2012
State estimation using wireless sensor networks (WSNs) is an important technique in many commerci... more State estimation using wireless sensor networks (WSNs) is an important technique in many commercial and military applications, in which a group of (nonidentical) sensors take noisy observations of system state and send back to a fusion center through wireless broadcasting for state estimation. In order to minimize the terminal estimation error covariance at the fusion center, a partial broadcasting policy should tell which sensors to broadcast at each stage. The limited battery allows each sensor to broadcast only a few times. The limited wireless communication bandwidth allows only a few sensors to broadcast at the same time. Due to these couplings, the optimal partial broadcasting policy is not clear in general. Despite the abundant applications of partial broadcasting policies, theoretical analysis is rare. In this technical note, we provide a first study on the properties of optimal partial broadcasting policies. When there is no packet drop, a good-sensor-late-broadcast (GSLB) rule is shown to perform optimally for both the scalar system and the vector system. When packet drops with positive probability, situations in which the GSLB rule may or may not perform optimally are analyzed. Under different dropping rates, the GSLB rule is compared with several other policies through simulations.
IEEE Transactions on Automatic Control, 2010
We consider autonomous partially observable Markov decision processes (POMDP) where the control a... more We consider autonomous partially observable Markov decision processes (POMDP) where the control action influences the observation process only. Assuming the state and observation processes are stationary, time homogenous and their corresponding supports are finite sets, we derive the transition probability kernel of the information state which is a Markov process over the belief space. Considering the belief entropy as the cost incurred by this Markov process, the optimal observability problem is posed as a Markov decision scheduling problem that minimizes the infinite horizon cost. This scheduling problem is shown to be equivalent to minimization of an entropy measure, called estimation entropy which is related to the invariant measure of the information state through mean ergodic theorem.
Mycological Research, 2004
The status of anaerobic zoosporic (Chytridiomycota) fungi along the entire digestive tract of she... more The status of anaerobic zoosporic (Chytridiomycota) fungi along the entire digestive tract of sheep was assessed both analytically and microscopically. Digest samples were taken from different segments of the digestive tracts of three newly killed sheep that previously had been used in experimental dietary studies. These digest samples were tested for the presence of rumen fungi by assessing the recovery of live fungi from the samples, direct observation of digested plant remains under the scanning electron microscope (SEM), and using a chitin assay as an estimation of fungal biomass. Live anaerobic fungi were recovered from the abomasum, small and large intestine, caecum and faeces of sheep, but not from the digest samples of rumen and omasum. However, SEM examination of the samples confirmed the presence of fungal structures from all of these organs. In the large intestine and caecum samples the observed sporangial structures were rounded and showed conspicuous surface pitting. Results of the chitin assay indicated that the anaerobic fungi might account for up to 20 % of the total microbial biomass in the rumen of sheep. The results of this study support the view that anaerobic fungi may be present as a resistant stage in the lower reaches of the digestive tract.
Mycological Research, 2004
Anaerobic fungi were isolated from both the rumen and faeces of nine sheep and a cow. A reliable ... more Anaerobic fungi were isolated from both the rumen and faeces of nine sheep and a cow. A reliable and simple method for the isolation of anaerobic fungi using 24 h rumen incubated milled straw as the inoculum source was developed. We also evaluate the use of chitin measurements as an assay of rumen fungal biomass. Chitin levels were determined from various sample sources (milled barley straw used as the fungal culture substrate in vitro ; plant particulate digests from the rumen (PLP) and centrifuged strained rumen fluid (CSRF) using both HPLC and colorimetric methods. Both methods were highly correlated and consequently the simpler colorimetric method was adopted for subsequent studies. There was also a high degree of correlation between anaerobic fungal cellulase activities with the assayed chitin content of milled barley straw cultures over 12 d of an in vitro experiment. The colorimetric chitin assay protocol was then used to assess the diurnal variation and abundance of rumen fungi in in vivo assays. We assessed the distribution of chitin (mg g x1 dry matter) in various fractions of the strained rumen fluid (SRF) and PLP samples from the rumen of sheep. Chitin was detected in all fractions of strained rumen fluid but the main source of chitin in the samples may be attributed to the fungal biomass. We did not detect any significant differences in chitin levels over a 24 h sampling period. Finally, an SEM study on subsamples of milled straw and plant particulate matter used in the chitin assays, revealed that the pattern of the fungal development on substrate material differs from the culture medium to the rumen.
Animal Feed Science and Technology, 2006
The experiment was conducted to study the effects of dietary changes on anaerobic fungal populati... more The experiment was conducted to study the effects of dietary changes on anaerobic fungal population assessed by rumen chitin content as a marker. Four rumen fistulated sheep were fed different proportions (100:0, 70:30, 30:70 and 0:100) of chopped and pelleted lucerne in a 4 × 4 Latin square design. Samples of whole rumen contents were collected at 0, 4, 8, 16, 22 h post-feeding, and analysed for their particle associated and liquid associated chitin. In addition, rumen pH, VFA concentration and in sacco degradability of barley straw were also measured as some indices of rumen fermentation pattern. The amount of chitin (g/kg DM) in liquid associated fractions (LAF) was about three times higher than that in particle associated fractions (PAF). Changes in the level of chitin (g/kg DM) in LAF and PAF were not significant when different proportions of chopped and pelleted lucerne were included in the diet. Nevertheless, there was a higher level of chitin (g/kg DM) in the rumen of sheep fed a diet of whole chopped lucerne (WCL, 100:0) compared to that of whole pelleted lucerne (WPL, Abbreviations: ADFom, acid detergent fibre expressed exclusive of residual ash; DM, dry matter; ED, effective degradability; HCL, high chopped lucern; LCL, low chopped lucerne; LAC, liquid associated chitin; LAF, liquid associated fraction; Lignin (sa), acid detergent lignin determined by the sa (sulphuric acid) method; NDFom, neutral detergent fibre expressed exclusive of residual ash;
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Papers by Mohammad Rezaeian