Exploiting UEP in QAM-based BICM: interleaver and code design

In this paper we formally analyze the interleaver and code design for QAM-based BICM transmissions using the binary reflected Gray code. We develop analytical bounds on the bit error rate and we use them to predict the performance of BICM when unequal error protection (UEP) is introduced by the constellation labeling. Based on these bounds the optimum design of interleaver and code is found, and numerical results for representative configurations are presented. When the new design is used, the improvements may reach 2 dB, and they are obtained without any increase on the transceiver?s complexity. We also introduce the concept of generalized optimum distance spectrum convolutional codes, which are the optimum codes for QAM-based BICM transmissions.     

Power consumption of analog circuits: a tutorial

A systematic approach to the power consumption of analog circuits is presented. The power consumption is related to basic circuit requirements, as dynamic range, bandwidth, noise figure and sampling speed and is considering basic device and device scaling behavior. Several kinds of circuits are treated, as samplers, amplifiers, filters and oscillators. The objective is to derive lower bounds to power consumption in analog circuits, to be used as design targets when designing power-constrained analog systems.     

Inhibition of Human DHODH by 4‐Hydroxycoumarins,Fenamic Acids,and N‐(Alkylcarbonyl)anthranilic Acids Identified by Structure‐Guided Fragment Selection

A strategy that combines virtual screening and structure‐guided selection of fragments was used to identify three unexplored classes of human DHODH inhibitor compounds: 4‐hydroxycoumarins, fenamic acids, and N‐(alkylcarbonyl)anthranilic acids. Structure‐guided selection of fragments targeting the inner subsite of the DHODH ubiquinone binding site made these findings possible with screening of fewer than 300 fragments in a DHODH assay. Fragments from the three inhibitor classes identified were subsequently chemically expanded to target an additional subsite of hydrophobic character. All three classes were found to exhibit distinct structure–activity relationships upon expansion. The novel N‐(alkylcarbonyl)anthranilic acid class shows the most promising potency against human DHODH, with IC₅₀ values in the low nanomolar range. The structure of human DHODH in complex with an inhibitor of this class is presented.     

Selective Pharmacophore Models of Dopamine D1 and D2 Full Agonists Based on Extended Pharmacophore Features

This study is focused on the identification of structural features that determine the selectivity of dopamine receptor agonists toward D₁ and D₂ receptors. Selective pharmacophore models were developed for both receptors. The models were built by using projected pharmacophoric features that represent the main agonist interaction sites in the receptor (the Ser residues in TM5 and the Asp in TM3), a directional aromatic feature in the ligand, a feature with large positional tolerance representing the positively charged nitrogen in the ligand, and sets of excluded volumes reflecting the shapes of the receptors. The sets of D₁ and D₂ ligands used for modeling were carefully selected from published sources and consist of structurally diverse, conformationally rigid full agonists as active ligands together with structurally related inactives. The robustness of the models in discriminating actives from inactives was tested against four ensembles of conformations generated by using different established methods and different force fields. The reasons for the selectivity can be attributed to both geometrical differences in the arrangement of the features, e.g., different tilt angels of the π system, as well as shape differences covered by the different sets of excluded volumes. This work provides useful information for the design of new D₁ and D₂ agonists and also for comparative homology modeling of D₁ and D₂ receptors. The approach is general and could therefore be applied to other ligand–protein interactions for which no experimental protein structure is available.     

RHEOLOGICAL CHARACTERIZATION OF COMMERCIALLY PROCESSED FLUID MILKS

Flow profiles of commercially processed whole, two-percent, one-percent and nonfat milks with added solids as well as skim milk without added solids were measured using a rotational steady shear viscometer. Also tested were mixtures of concentrated skim milk added to skim milk over a range of 9.7% to 20.2% total solids. A shear rate range of 121 to 486 s^-1 was used with a cone and plate geometry. In all cases, linear plots of shear stress versus shear rate with small nonzero intercepts were obtained.     

Optimization of high-resolution continuous flow analysis for transient climate signals in ice cores

Over the past two decades, continuous flow analysis (CFA) systems have been refined and widely used to measure aerosol constituents in polar and alpine ice cores in very high-depth resolution. Here we present a newly designed system consisting of sodium, ammonium, dust particles, and electrolytic meltwater conductivity detection modules. The system is optimized for high-resolution determination of transient signals in thin layers of deep polar ice cores. Based on standard measurements and by comparing sections of early Holocene and glacial ice from Greenland, we find that the new system features a depth resolution in the ice of a few millimeters which is considerably better than other CFA systems. Thus, the new system can resolve ice strata down to 10 mm thickness and has the potential of identifying annual layers in both Greenland and Antarctic ice cores throughout the last glacial cycle.     

Embedment tests perpendicular to the grain �C optical measurements of deformation fields

This paper reveals additional knowledge on the bearing behaviour of single fastener connections. By means of non-contact full-field deformation measurements the deformation fields were recorded for different test configurations. It is shown that embedment is a very local phenomenon causing large stress concentrations and gradients in the dowel vicinity. However, timber as being considered a highly orthotropic material loaded in the weak planes appears to be able to redistribute stresses and to activate material outside the dowel vicinity. This causes the ultimate strength to be governed by the deformation ability underneath the dowel. This effect is not detectable in case of rather small specimen geometries, however, it becomes evident in case of specimens of structural sizes. Finite element simulations show localization effects to be much more evident in case of isotropic materials like steel, what verifies an apparent load-sharing effect for timber perpendicular-to-grain.     

Fatigue crack in large-scale tubular joints for offshore structures

Tubular members have been used for constructing offshore structures. Large-scale fatigue tests of welded tubular K-joints under the balanced in-plane bending brace were carried out to investigate the fatigue behavior of API 2W Gr.50 steel produced by POSCO. The experimental results were verified by numerical approaches and compared with the IIW, DnV RP-C203 and API RP 2A-WSD design curves. The test results based on the hot spot stress were in agreement with the design curves. The SCF factor for tubular K-jo...     

On Multirate DS-CDMA Schemes with Interference Cancellation

This paper investigates interference cancellation (IC) in direct-sequence code-division multiple access (DS-CDMA) systems that support multiple data rates. Two methods for implementing multiple data rates are considered. One is the use of mixed modulation and the other is the use of multicodes. We introduce and analyze a new approach that combines these multiple data rate systems with IC. The cancellation in the receiver is performed successively on each user, starting with the user received with the highest power. This procedure can in turn be iterated, forming a multistage scheme, with the number of iterations set as a design parameter. Our analysis employs a Gaussian approximation for the distribution of the interference, and it includes both the AWGN and the flat Rayleigh fading channel. The systems are also evaluated via computer simulations. Our analysis and simulations indicate that the IC schemes used in mixed modulation or multicode systems yield a performance close to the single BPSK user bound and, consequently, give a prospect of a considerable improvement in performance compared to systems employing matched filter detectors.     

Pulsewidth control loop in high-speed CMOS clock buffers

In high-speed CMOS clock buffer design, the duty cycle of a clock is liable to be changed when the clock passes through a multistage buffer because the circuit is not pure digital. Signal quality degradation is influenced by temperature and process deviation. In this paper, we propose a pulsewidth control loop to get required pulsewidth. To investigate the loop stability, a linearized small signal analysis model is used. Results of SPICE simulation show that the pulsewidth can be well controlled if the loop parameters are properly chosen. The pulsewidth can be easily adjusted to a desired value by sizing the ratio of transistor sizes in the current mirror of charge pump