Unit Gain Research Articles

Optimization of AP1000 power control system setpoints using genetic algorithm

The aim of this work is to obtain the optimum controller parameters in advanced mechanical shim (MSHIM) control system of AP1000. The MSHIM control system is designed to allow the AP1000 nuclear steam supply system (NSSS) to perform power change operations automatically. For the MSHIM control system, the lead-time constant and lead/lag ratio in the average coolant temperature (Tavg) controller, and rate/lag constant and low gain of nonlinear gain unit in the power mismatch controller are considered decision variables through the sensitivity analysis when minimizing the overshoot in the nuclear power and maximum absolute deviation between average coolant temperature and its target value. The multi-objective problem with four decision variables is translated into two subproblems. The lead-time constant and lead/lag ratio in the Tavg controller are firstly optimized by non-dominated sorting genetic algorithm (NSGA-II) with the power mismatch controller defeated. Then rate/lag constant and low gain in the power mismatch controller is optimized by NSGA-II with the optimized parameters in the Tavg controller. Dynamic simulations are performed based on a fast-running NSSS Control & Analysis Platform (NCAP) in each iteration of the optimization process to calculate the objective functions. The 10 percent step load increase transient from 90% to 100% full power is selected as simulation case for the optimization. The calculation results demonstrate that much better reactor control capabilities can be provided by MSHIM control system when employing the optimized control parameters.

Effect of different levels of palygorskite inclusion on pellet quality, growth performance and nutrient utilization in broilers

The aim of the present study was to investigate the effects of different levels of palygorskite on the pellet quality, growth performance and nutrient utilization in broilers. Three hundred one-day-old Arbor Acres broilers were randomly divided into five treatment groups with six replicates of ten broilers each for a 42-day feeding trial. The birds were fed diets supplemented with 0, 5, 10, 15 and 20g/kg palygorskite, respectively. The results showed that the hardness and durability index of pellets were improved (linear and quadratic, P<0.001) with the increasing level of palygorskite inclusion. The palygorskite supplementation improved average daily gain (ADG) and average daily feed intake (ADFI) of broilers (linear and quadratic, P<0.001). The broilers fed the diet supplemented with 10g/kg palygorskite had the highest ADG among groups. Compared with the control group, neither 5g/kg nor 10g/kg palygorskite inclusion affected feed per unit gain (F/G) of broilers. However, the F/G in grower period increased 1.6% with diet 15g/kg (1.83 vs 1.80) and 3.3% with diet 20g/kg (1.86 vs 1.80). The results indicated that palygorskite inclusion could enhance the pellet hardness and durability index, and improve the growth performance of broilers. In additional, the optimal level of supplemented palygorskite in the pellet diets of broilers was 10g/kg.

Investigation of the interaction between separate calcium feeding and phytase supplementation on growth performance, calcium intake, nutrient digestibility and energy utilisation in broiler starters

The interaction between separate calcium (Ca) feeding and phytase supplementation on performance, coefficient of apparent ileal digestibility (CAID) of nitrogen (N), starch, fat and phosphorus (P), total tract retention (TTR) of Ca and P, and apparent metabolisable energy (AME) in broiler starters was investigated. The effect of phytase on the CAID and TTR of P in birds with access to a separate Ca source was of particular interest. Five dietary Ca concentrations (1.3, 4.3, 7.3, 10.3 and 13.3g/kg) and two inclusion levels (0 or 1000 phytase units [FYT/kg] of feed) of a 6-phytase were evaluated in a 5×2 factorial arrangement of treatments. All diets, based on wheat and soybean meal, were formulated to be equivalent in respect of total and non-phytate P contents (5.7 and 3.0g/kg, respectively). A total of 480, one-day-old male broilers were allocated to 48 cages (8 birds/cage), and cages were randomly assigned to 10 dietary treatments. Birds were also provided with a source of Ca in a separate feed trough. Increasing dietary Ca concentration decreased (P<0.05) weight gain and feed intake in diets without phytase with a marked reduction in the diet with 13.3g Ca/kg, whereas in the phytase-supplemented diets, the reduction in both weight gain and feed intake was gradual up to 13.3g Ca/kg, resulting in a dietary Ca concentration×phytase interaction. Addition of phytase lowered (P<0.01) feed per unit gain at all dietary Ca concentrations. During d 8–14, d 15–21, and over the 21 d trial period, consumption of the separate Ca source was reduced (P<0.001) by increasing dietary Ca concentration, irrespective of phytase addition. Over the 21 d trial period, increasing dietary Ca above 4.3g/kg decreased (P<0.05) the total Ca intake (Ca from separate source plus Ca from feed) in diets without phytase, but the total Ca intake in phytase-supplemented diets were similar (P>0.05). Birds fed 1.3g Ca/kg diet showed the lowest (P<0.05) N digestibility, but similar (P>0.05) to the diets with 4.3g Ca/kg. No significant (P>0.05) effect of dietary Ca concentration on the CAID of starch, fat and GE was found. Whilst, increasing dietary Ca concentration reduced (P<0.05) P digestibility gradually in diets without and with phytase, the reduction in CAID of P was remarkable in the phytase-supplemented diet with 13.3g Ca/kg. Phytase addition enhanced CAID of N (P<0.05), fat and GE (P<0.01), AME and toe ash (P<0.05). Increasing dietary Ca to 10.3 and 13.3 reduced TTR of P in diets without phytase, whilst all the phytase supplemented diets showed similar (P>0.05) retention. There was no effect (P>0.05) of dietary Ca on AME and toe ash. The previously reported Ca-specific appetite in modern broilers and the ‘phosphoric’ and ‘extra-phosphoric’ effects of phytase were confirmed in this study. Importantly, the current work highlighted the additive outcome of separate Ca feeding and phytase addition.

Oriented gain graphs, line graphs and eigenvalues

A theory of orientation on gain graphs (voltage graphs) is developed to generalize the notion of orientation on graphs and signed graphs. Using this orientation scheme, the line graph of a gain graph is studied. For a particular family of gain graphs with complex units, matrix properties are established. As with graphs and signed graphs, there is a relationship between the incidence matrix of a complex unit gain graph and the adjacency matrix of the line graph.

Planar Pose Graph Optimization: Duality, Optimal Solutions, and Verification

Pose graph optimization (PGO) is the problem of estimating a set of poses from pairwise relative measurements. PGO is a nonconvex problem and, currently, no known technique can guarantee the computation of a global optimal solution. In this paper, we show that Lagrangian duality allows computing a globally optimal solution under conditions that are satisfied in most robotics applications and enables to certify optimality of a given estimate. Our first contribution is to frame planar PGO in the complex domain. This makes analysis easier and allows drawing connections with existing literature on unit gain graphs. The second contribution is to formulate and analyze the properties of the Lagrangian dual problem in the complex domain. Our analysis shows that the duality gap is connected to the number of zero eigenvalues of the penalized pose graph matrix. We prove that if this matrix has a single zero eigenvalue, then 1) the duality gap is zero, 2) the primal PGO problem has a unique solution (up to an arbitrary roto-translation), and 3) the primal solution can be computed by scaling an eigenvector of the penalized pose graph matrix. The third contribution is algorithmic: We leverage duality to devise and algorithm that computes the optimal solution when the penalized matrix has a single zero eigenvalue. We also propose a suboptimal variant when the zero eigenvalues are multiple. Finally, we show that duality provides computational tools to verify if a given estimate (e.g., computed using iterative solvers) is globally optimal. We conclude the paper with an extensive numerical analysis. Empirical evidence shows that, in the vast majority of cases (100% of the tests under noise regimes of practical robotics applications), the penalized pose graph matrix has a single zero eigenvalue; hence, our approach allows computing (or verifying) the optimal solution.

Comparative analysis of the intrinsic voltage gain and unit gain frequency between SOI and bulk FinFETs up to high temperatures

This paper presents an experimental analysis of the analog application figures of merit: the intrinsic voltage gain (AV) and unit gain frequency, focusing on the performance comparison between silicon triple gate pFinFET devices, which were processed on both Si and Silicon-On-Insulator (SOI) substrates. The high temperature (from 25°C to 150°C) influence and different channel lengths and fin widths were also taken into account. While the temperature impact on the intrinsic voltage gain (AV) is limited, the unit gain frequency was strongly affected due to the carrier mobility degradation at higher temperatures, for both p- and n-type FinFET structures. In addition, the pFinFETs showed slightly larger AV values compared to the n-type counterparts, whereby the bulk FinFETs presented a higher dispersion than the SOI FinFETs.

Influence of feed form and particle size on performance, nutrient utilisation, and gastrointestinal tract development and morphometry in broiler starters fed maize-based diets

The influence of feed form and particle size on the performance, coefficient of apparent ileal digestibility (CAID) of nutrients, apparent metabolisable energy (AME) and intestinal morphology in broiler starters fed maize-based diets was examined in this study. Two feed forms (mash and pellet) and three particle sizes (fine, medium and coarse) were evaluated in a 2×3 factorial arrangement of treatments. Birds fed pelleted diets had higher (P<0.05) weight gain and feed intake than those fed mash diets. In mash diets, fine grinding resulted in lower (P<0.05) feed per unit gain compared to medium and coarse grinding, whereas, in pelleted diets, there was no effect (P>0.05) of particle size. Gizzard pH was not influenced (P>0.05) by particle size in mash diets, but fine grinding increased (P<0.05) gizzard pH compared to medium and coarse grinding in pelleted diets. Pelleting reduced (P<0.05) the CAID of nitrogen but increased (P<0.05) the ileal fat digestibility. Particle size had no effect (P>0.05) on CAID of starch and AME in mash diets, but in pelleted diets, pellets made from medium and coarsely ground maize showed higher (P<0.05) starch digestibility. Coarse grinding resulted in higher (P<0.05) AME in pelleted diets. Feeding pelleted diets reduced (P<0.05) the CAID of calcium and phosphorus, but increased (P<0.05) that of sodium. Medium and coarse grindings resulted in higher (P<0.05) calcium digestibility than fine grinding. Feeding pelleted diets reduced (P<0.05 to 0.001) the relative length of all small intestinal segments and the relative weight of pancreas, proventriculus, and gizzard. Medium and coarse grinding increased (P<0.05) the gizzard weight compared to fine grinding. In both the duodenum and jejunum, birds fed pelleted diets had greater (P<0.05) villus height than those fed mash diets. Goblet cell number in duodenum was higher (P<0.05) in birds fed diets containing fine particles compared to those fed medium and coarse particle sizes. The crypt depth in jejunum was greater (P<0.05) in birds fed pelleted diets. Overall, the present data showed that coarse grinding of maize, through enhanced gizzard development and functionality, is beneficial to nutrient and energy utilisation and growth performance in broilers fed pelleted diets.

A microphone array beamforming-based system for multi-talker speech separation

This paper presents a Multichannel Speech Separation System (MCSS) based on new beamforming frequency domain method. The beamformer exploits the spatial properties of the source signals using a microphone array. Therefore, it is based on a prior knowledge of the position of the speakers relative to the array. The proposed beamformer is defined with two processing steps: the first one is to keep a unit gain of the desired signal and the other blocks the wanted signal and minimises the output power of the interferences within only one step. In order to separate multiple speakers, multiple beamformers are used simultaneously, where a beamformer is computed for each source considering the remaining sources as interferers. We test and evaluate the proposed MCSS on real recording mixtures extracted from 'Multichannel In-Car Speech Database'. The experimental results proved the effectiveness of the proposed system in terms of speech separation. The quality of speech will be improved compared to the state-of-the-art.

Cost-effectiveness Analysis of Insulin Detemir Compared to Neutral Protamine Hagedorn (NPH) in Patients with Type 1 and Type 2 Diabetes Mellitus in Portugal

Objectives: To estimate the short-term (1 year) cost-effectiveness of Insulin Detemir (IDet) compared with Neutral Protamine Hagedorn (NPH) insulin for Type 1 (T1DM) and Type 2 Diabetes Mellitus (T2DM) in Portugal. Methods: A short-term cost-effectiveness model was adapted to the Portuguese National Health System (NHS), to estimate the Incremental Cost-Effectiveness Ratio (ICER) of IDet vs. NPH in terms of euros per quality-adjusted life years (€/QALY) gained. Non-severe hypoglycemia (NSH) rate for both diabetes types, and weight change, only for T2DM, were the clinical benefit variables. Three scenarios were estimated in which NPH was assigned three different values corresponding to a cohort of recent insulinization and a cohort of long-run insulinization from the UK Hypoglycemia Study and from a Spanish observational study. For all scenarios, the hypoglycemia Rate Ratio (RR) for T1DM was based on the CADTH Technology Report while for T2DM it was based on the head-to-head NCT00104182 randomized clinical trial. For T2DM, weight gain was also included in the model, based on the same RCT. Disutility values to calculate quality-adjusted life years (QALYs) were associated to NSH events and to BMI unit gain. Costs (Euros 2014), estimated from the perspective of the Portuguese NHS, included only insulin treatment and mild hypoglycemia management. Results: For the three scenarios a range of 0.025 – 0.076 QALYs for T1DM and 0.014 – 0.051 QALYs for T2DM were gained for IDet vs. NPH due to NSH and weight gain avoidance, in return of an incremental cost of €159.38 - €248.98 for T1DM and €209.66 – €274.44 for T2DM. This resulted in IDet vs. NPH ICER ranging between €2,096.23 and €9,936.98/QALY for T1DM and €4,145.75 and €19,999.87/QALY for T2DM. Conclusions: IDet appears as a cost-effective alternative to NPH in Portugal for T1DM and T2DM in all considered scenarios due to lower hypoglycemic rate and less weight gain.

Cost-Effectiveness Analysis of Insulin Detemir Compared to Neutral Protamine Hagedorn (NPH) in Patients with Type 1 and Type 2 Diabetes Mellitus in Spain.

IntroductionAn Excel® (Microsoft Corporation) model was adapted to estimate the short-term (1-year) cost effectiveness of insulin detemir (IDet) versus neutral protamine Hagedorn (NPH) insulin in patients initiating insulin treatment with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) in Spain.MethodsClinical benefits included the non-severe hypoglycemia rate for T1DM and T2DM, and weight change for T2DM. Three scenarios were included with different hypoglycemia rates estimated on the basis of clinical trials and observational studies. Costs, estimated from perspective of the Spanish Public Healthcare System (Euros 2014), included insulin treatment and non-severe hypoglycemia management costs. Non-severe hypoglycemia, defined as a self-managed event, implied the use of extra glucose testing strips and a general practitioner visit during the week following the event for 25% of patients. An average disutility value was associated to non-severe hypoglycemia events and, for T2DM, to one body mass index unit gain to calculate quality-adjusted life years (QALYs).ResultsFor the three scenarios a range of 0.025–0.076 QALYs for T1DM and 0.014–0.051 QALYs for T2DM were gained for IDet versus NPH due to non-severe hypoglycemia and weight gain avoidance, in return of an incremental cost of €145–192 for T1DM and €128–206 for T2DM. This resulted in the IDet versus NPH incremental cost-effectiveness ratio (ICER) ranging between €1910/QALY and €7682/QALY for T1DM and €2522/QALY and €15,009/QALY for T2DM.ConclusionIDet was a cost-effective alternative to NPH insulin in the first year of treatment of patients with T1DM and patients with T2DM in Spain, with ICERs under the threshold value commonly accepted in Spain (€30,000/QALY).FundingNovo Nordisk.Electronic supplementary materialThe online version of this article (doi:10.1007/s13300-015-0143-x) contains supplementary material, which is available to authorized users.

How ideas work: memes and institutional material in the first 100 years of the neighborhood unit

This paper reviews the history of the neighborhood unit idea, primarily in the United States and United Kingdom, as a means to examine how urban design ideas work. It argues that ideas like the neighborhood unit gain their power by framing the institutional material we create to help us cope with work. Institutional material refers to cultural product that conditions human action. Types of institutional material in urban design include practice norms, professional communities, and governance structures. Although the neighborhood unit emerged through a transatlantic network of planners and designers, the institutional material it framed was particular, local, and contingent. Ultimately, the paper argues that the neighborhood unit grew out of institutional material in the early 20th century that itself was influenced by the garden city, and that both neighborhood unit and garden city ideas continued to shape new institutional material in subsequent decades.

Syntheses, Spectroscopic, Electrochemical, and Third-Order Nonlinear Optical Studies of a Hybrid Tris{ruthenium(alkynyl)/(2-phenylpyridine)}iridium Complex.

The synthesis of fac-[Ir{N,C1′-(2,2′-NC5H4C6H3-5′-C≡C-1-C6H2-3,5-Et2-4-C≡CC6H4-4-C≡CH)}3] (10), which bears pendant ethynyl groups, and its reaction with [RuCl(dppe)2]PF6 to afford the heterobimetallic complex fac-[Ir{N,C1′-(2,2′-NC5H4C6H3-5′-C≡C-1-C6H2-3,5-Et2-4-C≡CC6H4-4-C≡C-trans-[RuCl(dppe)2])}3] (11) is described. Complex 10 is available from the two-step formation of iodo-functionalized fac-tris[2-(4-iodophenyl)pyridine]iridium(III) (6), followed by ligand-centered palladium-catalyzed coupling and desilylation reactions. Structural studies of tetrakis[2-(4-iodophenyl)pyridine-N,C1′](μ-dichloro)diiridium 5, 6, fac-[Ir{N,C1′-(2,2′-NC5H4C6H3-5′-C≡C-1-C6H2-3,5-Et2-4-C≡CH)}3] (8), and 10 confirm ligand-centered derivatization of the tris(2-phenylpyridine)iridium unit. Electrochemical studies reveal two (5) or one (6–10) Ir-centered oxidations for which the potential is sensitive to functionalization at the phenylpyridine groups but relatively insensitive to more remote derivatization. Compound 11 undergoes sequential Ru-centered and Ir-centered oxidation, with the potential of the latter significantly more positive than that of Ir(N,C′-NC5H4-2-C6H4-2)3. Ligand-centered π–π* transitions characteristic of the Ir(N,C′-NC5H4-2-C6H4-2)3 unit red-shift and gain in intensity following the iodo and alkynyl incorporation. Spectroelectrochemical studies of 6, 7, 9, and 11 reveal the appearance in each case of new low-energy LMCT bands following formal IrIII/IV oxidation preceded, in the case of 11, by the appearance of a low-energy LMCT band associated with the formal RuII/III oxidation process. Emission maxima of 6–10 reveal a red-shift upon alkynyl group introduction and arylalkynyl π-system lengthening; this process is quenched upon incorporation of the ligated ruthenium moiety on proceeding to 11. Third-order nonlinear optical studies of 11 were undertaken at the benchmark wavelengths of 800 nm (fs pulses) and 532 nm (ns pulses), the results from the former suggesting a dominant contribution from two-photon absorption, and results from the latter being consistent with primarily excited-state absorption.

Inertia of complex unit gain graphs

Let T={z∈C:|z|=1} be a subgroup of the multiplicative group of all nonzero complex numbers C×. A T-gain graph is a triple Φ=(G,T,φ) consisting of a graph G=(V,E), the circle group T and a gain function φ:E→→T such that φ(eij)=φ(eji)−1=φ(eji)¯. The adjacency matrix A(Φ) of the T-gain graph Φ=(G,φ) of order n is an n × n complex matrix (aij), whereaij={φ(eij),ifviisadjacenttovj,0,otherwise.Evidently this matrix is Hermitian. The inertia of Φ is defined to be the triple In(Φ)=(i+(Φ),i−(Φ),i0(Φ)), where i+(Φ),i−(Φ),i0(Φ) are numbers of the positive, negative and zero eigenvalues of A(Φ) including multiplicities, respectively. In this paper we investigate some properties of inertia of T-gain graph.

Influence of separate feeding of calcium on nutrient digestibility, energy utilisation and performance of young broilers fed pelleted wheat-based diets

Six broiler starter diets, based on wheat and soybean meal, were formulated to contain 1.1 2.0, 4.0, 6.0, 8.0 and 10.0g calcium (Ca)/kg. All diets were equivalent in respect of total and non-phytate phosphorus contents (5.4 and 3.0g/kg, respectively). The influence of dietary treatments on the growth performance, coefficient of apparent ileal digestibility (CAID) of nitrogen (N), starch, fat and phosphorus (P), Ca retention and apparent metabolisable energy (AME) in broiler starters was evaluated. A total of 288, one-day-old male broilers (Ross 308) were allocated to 36 cages (8birds/cage), and cages were randomly assigned to 6 dietary treatments. Birds were also provided with a source of Ca in a separate feed trough. Birds fed the diet with 1.1g Ca/kg gained more (P<0.05) weight and tended (P=0.08) to have higher feed intake than those fed the diets with 8.0 and 10.0g Ca/kg. Increasing dietary Ca concentrations from 1.1 to 8.0g/kg increased (P<0.05) feed per unit gain, but diets with 1.1 and 10.0g/kg Ca resulted in similar (P>0.05) feed per unit gain. During d 8 to 14, d 15 to 21, and over the entire trial period of 21 d, birds fed Ca-deficient (6.0g Ca/kg and less) diets consumed more (P<0.001) of the separate Ca source. During the third week and over the 21 d trial period, total Ca intake (Ca from feed plus Ca from separate source) of birds fed Ca-insufficient diets was higher (P<0.05) than those fed diets with higher dietary Ca concentrations. Diets with 1.1g Ca/kg resulted in the highest (P<0.05) CAID of P. There was no effect (P>0.05) of dietary Ca on the retention of Ca and ash, AME and toe ash. The present data suggest that feeding broilers low Ca diets with access to a separate Ca source, is advantageous in terms of broiler performance, while maintaining bone mineralisation. The data also demonstrate that the provision of separate Ca source may hold promise for reducing the dietary P contents.

A-InGaZnO Thin-Film Transistor-Based Operational Amplifier for an Adaptive DC–DC Converter in Display Driving Systems

In this paper, we present an operational amplifier (op-amp) and a pulsewidth-modulation (PWM) controller fabricated with amorphous indium-gallium-zinc oxide thin-film transistors (a-InGaZnO TFTs), to build an adaptive dc-dc converter for display driving systems. The fabricated a-InGaZnO TFT presents electrical characteristics suitable for accomplishing an op-amp composed only with n-type TFTs to have an overall gain of 24.5 dB, a cutoff frequency of 6 kHz, and a unit gain frequency of 32 kHz operating at ±15 V. The fabricated op-amp is used to construct a comparator and an error amplifier on the glass, which are combined to realize a PWM controller. The resulting PWM controller can successfully control the output voltage of an external dc-dc converter that follows the input voltage to the error amplifier, and can operate at 100 Hz to control the duty ratio from 24.3% to 66.1% when the reference voltage varies from 2 to 6 V, respectively.

Design of High Performance Sample Hold Amplifier for Pipeline ADC

A fully-differential switched-capacitor sample-and-hold amplifier (SHA) used in a 10-bit 30-MS/s pipeline analog-to-digital converter (ADC) was designed using a 0.13-μm CMOS process. Flip-around architecture was used in the SHA circuit to lower the power consumption. A gain-boosted operational amplifier (OPAMP) was designed with a DC gain of 87 dB and a unit gain bandwidth of 388MHz at a phase margin of 75 degree. The simulated results have shown that the SHA circuit reaches a spurious free dynamic range (SFDR) of 94 dB and a signal-to-noise ratio (SNR) of 76 dB for a 10.18 MHz input signal with 30 MS/s sampling rate.

Fenugreek residue as nutraceutical and antibacterial agent in broiler ration

A study was conducted in broiler chicken for 6 weeks to find out the efficacy of fenugreek residue (FR) as an additive in poultry rations and to evaluate the nutraceutical property of FR as a replacement of antibiotic (AB) in broiler rations. Day-old broiler chicks (216) were divided into 9 treatment groups, each treatment group had 3 replicates with 8 birds in each replicate. The treatments were 0, 0.5, 1.0, 1.5 and 2.0 % FR with and without antibiotic (500 g of 10% oxytetracycline/tonne). At the end of 6 weeks (0 – 42 day), the body weight gain was comparable with the control, whereas significantly higher feed intake and poor FCR was found in 1.0% and 1.5% FR without AB group than the control. Slaughter studies with 6 birds/treatment group were conducted at the end of the experiment revealed that dressing %, giblet and abdominal fat (g/kg body weight) did not vary among the groups. The blood glucose was not influenced and muscle cholesterol levels reduced in all treatment groups than the control. The intestinal bacterial Escherichia coli and Clostridium spp. count was found to be reduced in FR without AB, however FR with AB fed birds have intestinal Clostridium content comparable (0.5 and 2.0% FR) or higher (1.0 and 1.5% FR) than the control. Inclusion of FR with AB provided better returns over that of control. Supplementation of FR up to 2% with or without AB (except 1.5% FR without AB) in feed improved the performance of birds and reduced the feed cost per unit gain.

Simulation of Fractional-Order Low-Pass Filters

The attenuation of standard analog low-pass filters corresponds to a multiple value of -6 decibels per octave. This quantified value is related to the order of the filter. The issue addressed here is concerned with the extension of integer orders to non integer orders, such that the attenuation of a low-pass filter can be continuously adjusted. Fractional differential systems are known to provide such asymptotic behaviors and many results about their simulation are available. But even for a fixed cutoff frequency, their combination does not generate an additive group with respect to the order and they involve stability problems. In this paper, a class of low-pass filters with orders between 0 (the filter is a unit gain) and 1 (standard one-pole filter) is defined to restore these properties. These infinite dimensional filters are not fractional differential but admit some well-posed representations into weighted integrals of standard one-pole filters. Based on this, finite dimensional approximations are proposed and recast into the framework of statespace representations-space representations. A special care is given to reduce the computational complexity, through the dimension of the state. In practice, this objective is reached for the complete family, without damaging the perceptive quality, with dimension 13. Then, an accurate low-cost digital version of this family is built in the time-domain. The accuracy of the digital filters is verified on the complete range of parameters (cutoff frequencies and fractional orders). Moreover, the stability is guaranteed, even for time-varying parameters. As an application, a plugin has been implemented which provides a new audio tool for tuning the cutoff frequency and the asymptotic slope in a continuous way. As a very special application, choosing a one-half order combined with a low cutoff frequency (20 Hz or less), the filter fed with a white noise provides a pink noise generator.

VCCS controlled LDO with small on-chip capacitor

A stable LDO using VCCS (voltage control current source) is presented. The LDO is designed and implemented on GF 2P4M 0.35 μm CMOS technology. Compared with a previous compensation scheme, VCCS can implement a real stable LDO with a small on-chip capacitor of 1 pF, whose stability is not affected by the variable ESR (equivalent series resistance) of the output capacitor. The unit gain frequency of the LDO loop can achieve 1.5 MHz, improving the transient response. The PSR of the LDO is larger than 45 dB within 0–40 kHz. The static current of the LDO at heavy load of 100 mA is 57 μA and the dropout voltage of the LDO is 150 mV. Experimental results show that a setting time of 10 μs is achieved, and the variation of output voltage is smaller than 35 mV for a 100 mA load step in transient response of the LDO.

Numerical Synthesis of an Optimal Low-Sidelobe Beam Pattern for a Microphone Array

This letter describes a numerical algorithm for synthesizing optimal low-sidelobe beampatterns. The pattern synthesis problem is formulated as a constrained optimization that minimizes the spatially weighted energy arriving at the array subject to unit gain in the look direction and a constant sidelobe level. The weighting takes on the form of a sensor correlation matrix, parameterized between uncorrelated sensor noise and correlated signal arrival terms according to a balancing factor. Setting the balancing factor to its extreme values of 0 and 1, produces, respectively, the optimal Riblet-Chebyshev and Delay-and-Sum type beamformers. In between, the method generates a low-sidelobe beamformer with varying beamwidths that provides a trade-off between White Noise Gain and Directivity Index. Simulation examples demonstrate optimal and intermediate designs for uniform and non-uniform sensor spacings.