The Measurement of Technical Efficiency and Effective Factors in Cucumber Greenhouse (Case Study: Eastern Azarbayjan Province)

The purpose of this study was to estimate technical efficiency of cucumber greenhouses in Eastern Azarbayjan. In economic literature, it means the ratio of maximum output to the inputs. The objective of this research was to determinate the effective factors influencing it's inefficiency. The method of determination of deterministic and stochastic technical efficiency is corrected ordinary least squares (COLS) and maximum likelihood (ML) respectively. The average of technical efficiency in province’s cucumber greenhouse is approximately about 57 and 93 percent for deterministic and stochastic frontier method respectively. Production types had positive influence on technical inefficiency whereas experience of manager have negative influence on technical inefficiency

Application of Reduced State Sequence Estimation to Terrestrial Digital Radio Links

Applications of reduced state sequence estimation (RSSE) to the design of receivers for terrestrial digital radio links employing trellis coded modulation (TCM) are investigated and compared to standard techniques that separately perform the specific tasks of equalization and TCM decoding. Numerical results based on computer simulation are provided, showing that a significant performance improvement is attainable by a receiver based on RSSE for typical radio-link channels affected by intersymbol interference (ISI) and thermal noise. In addition, special attention is devoted to the receiver complexity, expressed in terms of number of equalizer taps and number of states of the assumed trellis diagram. Most of the potential gain is shown to be attainable by receivers of affordable complexit

Maximum-Likelihood Semiblind Equalization of Doubly Selective Channels Using the EM Algorithm

Maximum-likelihood semi-blind joint channel estimation and equalization for doubly selective channels and single-carrier systems is proposed. We model the doubly selective channel as an FIR filter where each filter tap is modeled as a linear combination of basis functions. This channel description is then integrated in an iterative scheme based on the expectation-maximization (EM) principle that converges to the channel description vector estimation. We discuss the selection of the basis functions and compare various functions sets. To alleviate the problem of convergence to a local maximum, we propose an initialization scheme to the EM iterations based on a small number of pilot symbols. We further derive a pilot positioning scheme targeted to reduce the probability of convergence to a local maximum. Our pilot positioning analysis reveals that for high Doppler rates it is better to spread the pilots evenly throughout the data block (and not to group them) even for frequency-selective channels. The resulting equalization algorithm is shown to be superior over previously proposed equalization schemes and to perform in many cases close to the maximum-likelihood equalizer with perfect channel knowledge. Our proposed method is also suitable for coded systems and as a building block for Turbo equalization algorithms