Linear MMSE-Optimal Turbo Equalization Using Context Trees

Formulations of the turbo equalization approach to iterative equalization and decoding vary greatly when channel knowledge is either partially or completely unknown. Maximum aposteriori probability (MAP) and minimum mean square error (MMSE) approaches leverage channel knowledge to make explicit use of soft information (priors over the transmitted data bits) in a manner that is distinctly nonlinear, appearing either in a trellis formulation (MAP) or inside an inverted matrix (MMSE). To date, nearly all adaptive turbo equalization methods either estimate the channel or use a direct adaptation equalizer in which estimates of the transmitted data are formed from an expressly linear function of the received data and soft information, with this latter formulation being most common. We study a class of direct adaptation turbo equalizers that are both adaptive and nonlinear functions of the soft information from the decoder. We introduce piecewise linear models based on context trees that can adaptively approximate the nonlinear dependence of the equalizer on the soft information such that it can choose both the partition regions as well as the locally linear equalizer coefficients in each region independently, with computational complexity that remains of the order of a traditional direct adaptive linear equalizer. This approach is guaranteed to asymptotically achieve the performance of the best piecewise linear equalizer and we quantify the MSE performance of the resulting algorithm and the convergence of its MSE to that of the linear minimum MSE estimator as the depth of the context tree and the data length increase.Comment: Submitted to the IEEE Transactions on Signal Processin

Export of recombinant proteins in Escherichia coli using ABC transporter with an attached lipase ABC transporter recognition domain (LARD)

<p>Abstract</p> <p>Background</p> <p>ATP binding cassette (ABC) transporter secretes the protein through inner and outer membranes simultaneously in gram negative bacteria. Thermostable lipase (TliA) of <it>Pseudomonas fluorescens </it>SIK W1 is secreted through the ABC transporter. TliA has four glycine-rich repeats (GGXGXD) in its C-terminus, which appear in many ABC transporter-secreted proteins. From a homology model of TliA derived from the structure of <it>P. aeruginosa </it>alkaline protease (AprA), lipase ABC transporter domains (LARDs) were designed for the secretion of fusion proteins.</p> <p>Results</p> <p>The LARDs included four glycine-rich repeats comprising a β-roll structure, and were added to the C-terminus of test proteins. Either Pro-Gly linker or Factor Xa site was added between fusion proteins and LARDs. We attached different length of LARDs such as LARD0, LARD1 or whole TliA (the longest LARD) to three types of proteins; green fluorescent protein (GFP), epidermal growth factor (EGF) and cytoplasmic transduction peptide (CTP). These fusion proteins were expressed in <it>Escherichia coli </it>together with ABC transporter of either <it>P. fluorescens </it>or <it>Erwinia chrysanthemi</it>. Export of fusion proteins with the whole TliA through the ABC transporter was evident on the basis of lipase enzymatic activity. Upon supplementation of <it>E. coli </it>with ABC transporter, GFP-LARDs and EGF-LARDs were excreted into the culture supernatant.</p> <p>Conclusion</p> <p>The LARDs or whole TliA were attached to C-termini of model proteins and enabled the export of the model proteins such as GFP and EGF in <it>E. coli </it>supplemented with ABC transporter. These results open the possibility for the extracellular production of recombinant proteins in <it>Pseudomonas </it>using LARDs or TliA as a C-terminal signal sequence.</p

Extension of the DG Model to the Second-Order Quantum Correction for Analysis of the Single-Charge Effect in Sub-10-nm MOS Devices

We extended the density-gradient (DG) model to include a second-order quantum correction (SOQC) term. The DG model has been widely used as a device simulation model capable of simulating quantum effects in efficient way. However, when only the first order quantum correction term is considered in the DG model, it is difficult to accurately describe device characteristics such as carrier density or potential fluctuation in the narrow region due to discrete charges such as dopants and interface traps. Thus, we extended the DG model to the SOQC, implemented it as a three-dimensional (3D) simulator, and compared the simulation results for sub-10-nm devices, which have a single point charge, in the DG model and the 3D Schr&#x00F6;dinger&#x2013;Poisson (SP) solver. Through this, we identified that the DG extended to SOQC well reproduces the SP simulation results in terms of both capacitance&#x2013;voltage (C&#x2013;V) and local fluctuation in electron density

Iterative Estimation of Sparse and Doubly-Selective Multi-input Multi-output (MIMO) Channel

Abstract—The estimation of doubly-selective channels is challenging since long channel impulse response should be estimated with a fast tracking speed. Provided that a structure of the channel response is sparse, i.e., only a few of channel gains are nonzero, a tracking performance of the channel estimator can be improved significantly by avoiding estimation of zero taps. In this paper, we study estimation of fast time-varying and long reverberant channels that have a sparse structure in multi-input multi-output (MIMO) systems. In order to exploit the sparse structure, we parameterize the locations of nonzero taps using a binary vector and incorporate it into the state-space system built upon auto-regressive (AR) modeling of the time-varying channel gains. Then, we derive a joint estimate of the binary vector and channel gains based on maximum likelihood (ML) criterion. Expectation maximization (EM) algorithm is derived to find a sparse structure and channel gains iteratively. According to the simulation study performed over MIMO Rician fading channels, the proposed sparse channel estimation technique outperforms the previous estimation schemes, especially when Doppler rate is high. I

Transformation of 2D Planes into 3D Soft and Flexible Structures with Embedded Electrical Functionality

Three-dimensional (3D) structures composed of flexible and soft materials have been in demand for implantable biomedical devices. However, the fabrication of 3D structures using microelectromechanical system (MEMS) techniques has limitations in terms of the materials and the scale of the structures. Here, a technique to selectively bond polydimethylsiloxane (PDMS) and parylene-C by plasma treatment is reported, with which two-dimensional structures that are fabricated using MEMS techniques are turned into 3D structures by the inflation of selectively non-bonded patterns. The bonding strength and the bonding mechanism were analyzed by mechanical tests and chemical analyses, respectively. We fabricated soft and flexible 3D structures with various patterns and dimensions, even with embedded electrical functions, including light emitting diodes and electrocorticogram electrodes. Based on these results, the flexible, soft, and MEMS-capable 3D structures that are obtained by the developed selective bonding technique are promising for applications in a wide range of biomedical applications. © 2019 American Chemical Society.FALS

Detector Mount Design for IGRINS

The Immersion Grating Infrared Spectrometer (IGRINS) is a near-infrared wide-band high-resolution spectrograph jointly developed by the Korea Astronomy and Space Science Institute and the University of Texas at Austin. IGRINS employs three HAWAII-2RG Focal Plane Array (H2RG FPA) detectors. We present the design and fabrication of the detector mount for the H2RG detector. The detector mount consists of a detector housing, an ASIC housing, a Field Flattener Lens (FFL) mount, and a support base frame. The detector and the ASIC housing should be kept at 65 K and the support base frame at 130 K. Therefore they are thermally isolated by the support made of GFRP material. The detector mount is designed so that it has features of fine adjusting the position of the detector surface in the optical axis and of fine adjusting yaw and pitch angles in order to utilize as an optical system alignment compensator. We optimized the structural stability and thermal characteristics of the mount design using computer-aided 3D modeling and finite element analysis. Based on the structural and thermal analysis, the designed detector mount meets an optical stability tolerance and system thermal requirements. Actual detector mount fabricated based on the design has been installed into the IGRINS cryostat and successfully passed a vacuum test and a cold test