On Nonconvex Decentralized Gradient Descent
2016-08-01
difference between each local point and their global average is subject to a bound proportional to the step size. This note then establishes similar...estimation, and control. When fi’s are convex, the existing algorithms include the (sub)gradient meth- ods [5], [7], [10], [11], [18], [14], [15], and the...set of n nodes and E is the edge set. Any edge (i, j) ∈ E represents an arc between node i and node j. Let x(i) ∈ Rp denote the local copy of x at node
Improving dimensionality reduction with spectral gradient descent.
Memisevic, Roland; Hinton, Geoffrey
2005-01-01
We introduce spectral gradient descent, a way of improving iterative dimensionality reduction techniques. The method uses information contained in the leading eigenvalues of a data affinity matrix to modify the steps taken during a gradient-based optimization procedure. We show that the approach is able to speed up the optimization and to help dimensionality reduction methods find better local minima of their objective functions. We also provide an interpretation of our approach in terms of the power method for finding the leading eigenvalues of a symmetric matrix and verify the usefulness of the approach in some simple experiments.
Error analysis of stochastic gradient descent ranking.
Chen, Hong; Tang, Yi; Li, Luoqing; Yuan, Yuan; Li, Xuelong; Tang, Yuanyan
2013-06-01
Ranking is always an important task in machine learning and information retrieval, e.g., collaborative filtering, recommender systems, drug discovery, etc. A kernel-based stochastic gradient descent algorithm with the least squares loss is proposed for ranking in this paper. The implementation of this algorithm is simple, and an expression of the solution is derived via a sampling operator and an integral operator. An explicit convergence rate for leaning a ranking function is given in terms of the suitable choices of the step size and the regularization parameter. The analysis technique used here is capacity independent and is novel in error analysis of ranking learning. Experimental results on real-world data have shown the effectiveness of the proposed algorithm in ranking tasks, which verifies the theoretical analysis in ranking error.
Efficient Sensor Placement Optimization Using Gradient Descent and Probabilistic Coverage
Directory of Open Access Journals (Sweden)
Vahab Akbarzadeh
2014-08-01
Full Text Available We are proposing an adaptation of the gradient descent method to optimize the position and orientation of sensors for the sensor placement problem. The novelty of the proposed method lies in the combination of gradient descent optimization with a realistic model, which considers both the topography of the environment and a set of sensors with directional probabilistic sensing. The performance of this approach is compared with two other black box optimization methods over area coverage and processing time. Results show that our proposed method produces competitive results on smaller maps and superior results on larger maps, while requiring much less computation than the other optimization methods to which it has been compared.
Design Gradient Descent Optimal Sliding Mode Control of Continuum Robots
Directory of Open Access Journals (Sweden)
Farzin Piltan
2012-08-01
Full Text Available In this research, a new approach for gradient descent optimal sliding mode controller for continuum robots is proposed. Based on the new dynamic models developed, a novel technique for nonlinear control of continuum manipulators to be employed in various situations has also been proposed and developed. A section of a continuum arm is modeled using lumped model elements (masses, springs and dampers and control by nonlinear methodology (sliding mode method and optimization the sliding surface slope by gradient descent method. It is shown that this type of control methodology, although used to a certain model, can be used to conveniently control the dynamics of the arm with suitable tradeoff in accuracy of modeling. This relatively controller is more plausible to implement in an actual real-time when compared to other techniques of nonlinear controller methodology of continuum arms. Principles of sliding mode methodology is based on derive the sliding surface slope and nonlinear dynamic model and applied in the system. Based on the gradient descent optimization method, the sliding surface slope and gain updating factor has been developed in certain and partly uncertain continuum robots. This methodology is represented in certain and uncertain area whose only optimization for certain area and test this optimization for uncertainty. The new techniques proposed and methodologies adopted in this paper supported by MATLAB/SIMULINK results represent a significant contribution to the field of design an optimized nonlinear sliding mode controller for continuum robots.
Accelerating deep neural network training with inconsistent stochastic gradient descent.
Wang, Linnan; Yang, Yi; Min, Renqiang; Chakradhar, Srimat
2017-09-01
Stochastic Gradient Descent (SGD) updates Convolutional Neural Network (CNN) with a noisy gradient computed from a random batch, and each batch evenly updates the network once in an epoch. This model applies the same training effort to each batch, but it overlooks the fact that the gradient variance, induced by Sampling Bias and Intrinsic Image Difference, renders different training dynamics on batches. In this paper, we develop a new training strategy for SGD, referred to as Inconsistent Stochastic Gradient Descent (ISGD) to address this problem. The core concept of ISGD is the inconsistent training, which dynamically adjusts the training effort w.r.t the loss. ISGD models the training as a stochastic process that gradually reduces down the mean of batch's loss, and it utilizes a dynamic upper control limit to identify a large loss batch on the fly. ISGD stays on the identified batch to accelerate the training with additional gradient updates, and it also has a constraint to penalize drastic parameter changes. ISGD is straightforward, computationally efficient and without requiring auxiliary memories. A series of empirical evaluations on real world datasets and networks demonstrate the promising performance of inconsistent training. Copyright © 2017 Elsevier Ltd. All rights reserved.
Gradient descent learning in and out of equilibrium
International Nuclear Information System (INIS)
Caticha, Nestor; Araujo de Oliveira, Evaldo
2001-01-01
Relations between the off thermal equilibrium dynamical process of on-line learning and the thermally equilibrated off-line learning are studied for potential gradient descent learning. The approach of Opper to study on-line Bayesian algorithms is used for potential based or maximum likelihood learning. We look at the on-line learning algorithm that best approximates the off-line algorithm in the sense of least Kullback-Leibler information loss. The closest on-line algorithm works by updating the weights along the gradient of an effective potential, which is different from the parent off-line potential. A few examples are analyzed and the origin of the potential annealing is discussed
Automation for Accommodating Fuel-Efficient Descents in Constrained Airspace
Coopenbarger, Richard A.
2010-01-01
Continuous descents at low engine power are desired to reduce fuel consumption, emissions and noise during arrival operations. The challenge is to allow airplanes to fly these types of efficient descents without interruption during busy traffic conditions. During busy conditions today, airplanes are commonly forced to fly inefficient, step-down descents as airtraffic controllers work to ensure separation and maximize throughput. NASA in collaboration with government and industry partners is developing new automation to help controllers accommodate continuous descents in the presence of complex traffic and airspace constraints. This automation relies on accurate trajectory predictions to compute strategic maneuver advisories. The talk will describe the concept behind this new automation and provide an overview of the simulations and flight testing used to develop and refine its underlying technology.
Understanding and Optimizing Asynchronous Low-Precision Stochastic Gradient Descent
De Sa, Christopher; Feldman, Matthew; Ré, Christopher; Olukotun, Kunle
2018-01-01
Stochastic gradient descent (SGD) is one of the most popular numerical algorithms used in machine learning and other domains. Since this is likely to continue for the foreseeable future, it is important to study techniques that can make it run fast on parallel hardware. In this paper, we provide the first analysis of a technique called Buckwild! that uses both asynchronous execution and low-precision computation. We introduce the DMGC model, the first conceptualization of the parameter space that exists when implementing low-precision SGD, and show that it provides a way to both classify these algorithms and model their performance. We leverage this insight to propose and analyze techniques to improve the speed of low-precision SGD. First, we propose software optimizations that can increase throughput on existing CPUs by up to 11×. Second, we propose architectural changes, including a new cache technique we call an obstinate cache, that increase throughput beyond the limits of current-generation hardware. We also implement and analyze low-precision SGD on the FPGA, which is a promising alternative to the CPU for future SGD systems. PMID:29391770
Manifold regularized discriminative nonnegative matrix factorization with fast gradient descent.
Guan, Naiyang; Tao, Dacheng; Luo, Zhigang; Yuan, Bo
2011-07-01
Nonnegative matrix factorization (NMF) has become a popular data-representation method and has been widely used in image processing and pattern-recognition problems. This is because the learned bases can be interpreted as a natural parts-based representation of data and this interpretation is consistent with the psychological intuition of combining parts to form a whole. For practical classification tasks, however, NMF ignores both the local geometry of data and the discriminative information of different classes. In addition, existing research results show that the learned basis is unnecessarily parts-based because there is neither explicit nor implicit constraint to ensure the representation parts-based. In this paper, we introduce the manifold regularization and the margin maximization to NMF and obtain the manifold regularized discriminative NMF (MD-NMF) to overcome the aforementioned problems. The multiplicative update rule (MUR) can be applied to optimizing MD-NMF, but it converges slowly. In this paper, we propose a fast gradient descent (FGD) to optimize MD-NMF. FGD contains a Newton method that searches the optimal step length, and thus, FGD converges much faster than MUR. In addition, FGD includes MUR as a special case and can be applied to optimizing NMF and its variants. For a problem with 165 samples in R(1600), FGD converges in 28 s, while MUR requires 282 s. We also apply FGD in a variant of MD-NMF and experimental results confirm its efficiency. Experimental results on several face image datasets suggest the effectiveness of MD-NMF.
Minimum-Cost Aircraft Descent Trajectories with a Constrained Altitude Profile
Wu, Minghong G.; Sadovsky, Alexander V.
2015-01-01
An analytical formula for solving the speed profile that accrues minimum cost during an aircraft descent with a constrained altitude profile is derived. The optimal speed profile first reaches a certain speed, called the minimum-cost speed, as quickly as possible using an appropriate extreme value of thrust. The speed profile then stays on the minimum-cost speed as long as possible, before switching to an extreme value of thrust for the rest of the descent. The formula is applied to an actual arrival route and its sensitivity to winds and airlines' business objectives is analyzed.
On Scalable Deep Learning and Parallelizing Gradient Descent
AUTHOR|(CDS)2129036; Möckel, Rico; Baranowski, Zbigniew; Canali, Luca
Speeding up gradient based methods has been a subject of interest over the past years with many practical applications, especially with respect to Deep Learning. Despite the fact that many optimizations have been done on a hardware level, the convergence rate of very large models remains problematic. Therefore, data parallel methods next to mini-batch parallelism have been suggested to further decrease the training time of parameterized models using gradient based methods. Nevertheless, asynchronous optimization was considered too unstable for practical purposes due to a lacking understanding of the underlying mechanisms. Recently, a theoretical contribution has been made which defines asynchronous optimization in terms of (implicit) momentum due to the presence of a queuing model of gradients based on past parameterizations. This thesis mainly builds upon this work to construct a better understanding why asynchronous optimization shows proportionally more divergent behavior when the number of parallel worker...
A new type of descent conjugate gradient method with exact line search
Hajar, Nurul; Mamat, Mustafa; Rivaie, Mohd.; Jusoh, Ibrahim
2016-06-01
Nowadays, conjugate gradient (CG) methods are impressive for solving nonlinear unconstrained optimization problems. In this paper, a new CG method is proposed and analyzed. This new CG method satisfies descent condition and its global convergence is established using exact line search. Numerical results show that this new CG method substantially outperforms the previous CG methods. This new CG method is considered robust, efficient and provided faster and stable convergence.
Fast alternating projected gradient descent algorithms for recovering spectrally sparse signals
Cho, Myung
2016-06-24
We propose fast algorithms that speed up or improve the performance of recovering spectrally sparse signals from un-derdetermined measurements. Our algorithms are based on a non-convex approach of using alternating projected gradient descent for structured matrix recovery. We apply this approach to two formulations of structured matrix recovery: Hankel and Toeplitz mosaic structured matrix, and Hankel structured matrix. Our methods provide better recovery performance, and faster signal recovery than existing algorithms, including atomic norm minimization.
Ionospheric forecasting model using fuzzy logic-based gradient descent method
Directory of Open Access Journals (Sweden)
D. Venkata Ratnam
2017-09-01
Full Text Available Space weather phenomena cause satellite to ground or satellite to aircraft transmission outages over the VHF to L-band frequency range, particularly in the low latitude region. Global Positioning System (GPS is primarily susceptible to this form of space weather. Faulty GPS signals are attributed to ionospheric error, which is a function of Total Electron Content (TEC. Importantly, precise forecasts of space weather conditions and appropriate hazard observant cautions required for ionospheric space weather observations are limited. In this paper, a fuzzy logic-based gradient descent method has been proposed to forecast the ionospheric TEC values. In this technique, membership functions have been tuned based on the gradient descent estimated values. The proposed algorithm has been tested with the TEC data of two geomagnetic storms in the low latitude station of KL University, Guntur, India (16.44°N, 80.62°E. It has been found that the gradient descent method performs well and the predicted TEC values are close to the original TEC measurements.
Accelerated gradient methods for constrained image deblurring
International Nuclear Information System (INIS)
Bonettini, S; Zanella, R; Zanni, L; Bertero, M
2008-01-01
In this paper we propose a special gradient projection method for the image deblurring problem, in the framework of the maximum likelihood approach. We present the method in a very general form and we give convergence results under standard assumptions. Then we consider the deblurring problem and the generality of the proposed algorithm allows us to add a energy conservation constraint to the maximum likelihood problem. In order to improve the convergence rate, we devise appropriate scaling strategies and steplength updating rules, especially designed for this application. The effectiveness of the method is evaluated by means of a computational study on astronomical images corrupted by Poisson noise. Comparisons with standard methods for image restoration, such as the expectation maximization algorithm, are also reported.
Dynamic gradient descent learning algorithms for enhanced empirical modeling of power plants
International Nuclear Information System (INIS)
Parlos, A.G.; Atiya, Amir; Chong, K.T.
1991-01-01
A newly developed dynamic gradient descent-based learning algorithm is used to train a recurrent multilayer perceptron network for use in empirical modeling of power plants. The two main advantages of the proposed learning algorithm are its ability to consider past error gradient information for future use and the two forward passes associated with its implementation, instead of one forward and one backward pass of the backpropagation algorithm. The latter advantage results in computational time saving because both passes can be performed simultaneously. The dynamic learning algorithm is used to train a hybrid feedforward/feedback neural network, a recurrent multilayer perceptron, which was previously found to exhibit good interpolation and extrapolation capabilities in modeling nonlinear dynamic systems. One of the drawbacks, however, of the previously reported work has been the long training times associated with accurate empirical models. The enhanced learning capabilities provided by the dynamic gradient descent-based learning algorithm are demonstrated by a case study of a steam power plant. The number of iterations required for accurate empirical modeling has been reduced from tens of thousands to hundreds, thus significantly expediting the learning process
SEARCH FOR THE BEST POWER CONTROL PROGRAM AT NPP WITH VVER-1000 USING GRADIENT DESCENT METHOD
Directory of Open Access Journals (Sweden)
S. N. Pelykh
2016-09-01
Full Text Available This article is regarded to the search for the best power control program at nuclear power plant (NPP with VVER- 1000 by gradient descent method for the objective function, which includes the criteria of efficiency, safety and damage. Criteria normalization to the maximum value is carried out when looking for the minimum of the objective function because criteria have different physical nature. There were chosen such objective criteria as depth of fuel burn-up, index of the fuel cladding damage and axial offset - the ratio of the energy at the top and bottom of the reactor core.
Block-Based Gradient Descent for Local Backlight Dimming and Flicker Reduction
DEFF Research Database (Denmark)
Burini, Nino; Mantel, Claire; Nadernejad, Ehsan
2014-01-01
Local backlight dimming technology is a two-fold improvement for LED backlit LCD screens that allows to reduce power consumption and increase visual quality. This paper presents a fast version of an iterative backlight dimming algorithm based on gradient descent search. The speed is increased...... by exploiting the local uniformity of backlight to reduce the complexity for determining the optimal backlight of a given image. The algorithm is adapted to video sequences by using the backlight of the previous frame as a starting point to calculate the backlight for the current frame. Fast variations...
Loizou, Nicolas
2017-12-27
In this paper we study several classes of stochastic optimization algorithms enriched with heavy ball momentum. Among the methods studied are: stochastic gradient descent, stochastic Newton, stochastic proximal point and stochastic dual subspace ascent. This is the first time momentum variants of several of these methods are studied. We choose to perform our analysis in a setting in which all of the above methods are equivalent. We prove global nonassymptotic linear convergence rates for all methods and various measures of success, including primal function values, primal iterates (in L2 sense), and dual function values. We also show that the primal iterates converge at an accelerated linear rate in the L1 sense. This is the first time a linear rate is shown for the stochastic heavy ball method (i.e., stochastic gradient descent method with momentum). Under somewhat weaker conditions, we establish a sublinear convergence rate for Cesaro averages of primal iterates. Moreover, we propose a novel concept, which we call stochastic momentum, aimed at decreasing the cost of performing the momentum step. We prove linear convergence of several stochastic methods with stochastic momentum, and show that in some sparse data regimes and for sufficiently small momentum parameters, these methods enjoy better overall complexity than methods with deterministic momentum. Finally, we perform extensive numerical testing on artificial and real datasets, including data coming from average consensus problems.
International Nuclear Information System (INIS)
Jia, Ningning; Lam, Edmund Y
2010-01-01
Inverse lithography technology (ILT) synthesizes photomasks by solving an inverse imaging problem through optimization of an appropriate functional. Much effort on ILT is dedicated to deriving superior masks at a nominal process condition. However, the lower k 1 factor causes the mask to be more sensitive to process variations. Robustness to major process variations, such as focus and dose variations, is desired. In this paper, we consider the focus variation as a stochastic variable, and treat the mask design as a machine learning problem. The stochastic gradient descent approach, which is a useful tool in machine learning, is adopted to train the mask design. Compared with previous work, simulation shows that the proposed algorithm is effective in producing robust masks
Ma, Huimin; Qiao, Yan; Shen, Chunshan
2017-10-01
Adaptive optics systems based on stochastic parallel gradient descent optimization (SPGD) have yet shown great potential on compensation of phase distortions induced by wave propagation through atmosphere turbulence. One of the key technique is increasing the converge rate of SPGD correction system. In the present study, it is shown that the convergence rate of the algorithm will be greatly reduced with the increase of the number of corrector units. In this paper, an improved SPGD optimization process which is based on Zernike-mode is developed. The optimized object is changed from the voltage to Zernike coefficient. Adaptive optics correction system simulation model base on SPGD for a laser beam projecting system, and the numerical simulation of compensation process of random atmosphere turbulence is proposed. To improve the converge speed, we explore to ameliorate the correction system by controlling the perturbation considering atmosphere aberration proportion. The results show that the system converges smoothly and increasingly after considering the aberration proportion by Zernike correction.
International Nuclear Information System (INIS)
Dong Bing; Ren Deqing; Zhang Xi
2011-01-01
An adaptive optics (AO) system based on a stochastic parallel gradient descent (SPGD) algorithm is proposed to reduce the speckle noises in the optical system of a stellar coronagraph in order to further improve the contrast. The principle of the SPGD algorithm is described briefly and a metric suitable for point source imaging optimization is given. The feasibility and good performance of the SPGD algorithm is demonstrated by an experimental system featured with a 140-actuator deformable mirror and a Hartmann-Shark wavefront sensor. Then the SPGD based AO is applied to a liquid crystal array (LCA) based coronagraph to improve the contrast. The LCA can modulate the incoming light to generate a pupil apodization mask of any pattern. A circular stepped pattern is used in our preliminary experiment and the image contrast shows improvement from 10 -3 to 10 -4.5 at an angular distance of 2λ/D after being corrected by SPGD based AO.
Quaternion-Based Kalman Filter for AHRS Using an Adaptive-Step Gradient Descent Algorithm
Directory of Open Access Journals (Sweden)
Li Wang
2015-09-01
Full Text Available This paper presents a quaternion-based Kalman filter for real-time estimation of the orientation of a quadrotor. Quaternions are used to represent rotation relationship between navigation frame and body frame. Processing of a 3-axis accelerometer using Adaptive-Step Gradient Descent (ASGD produces a computed quaternion input to the Kalman filter. The step-size in GD is set in direct proportion to the physical orientation rate. Kalman filter combines 3-axis gyroscope and computed quaternion to determine pitch and roll angles. This combination overcomes linearization error of the measurement equations and reduces the calculation cost. 3-axis magnetometer is separated from ASGD to independently calculate yaw angle for Attitude Heading Reference System (AHRS. This AHRS algorithm is able to remove the magnetic distortion impact. Experiments are carried out in the small-size flight controller and the real world flying test shows the proposed AHRS algorithm is adequate for the real-time estimation of the orientation of a quadrotor.
Tripathi, Ashish; McNulty, Ian; Shpyrko, Oleg G
2014-01-27
Ptychographic coherent x-ray diffractive imaging is a form of scanning microscopy that does not require optics to image a sample. A series of scanned coherent diffraction patterns recorded from multiple overlapping illuminated regions on the sample are inverted numerically to retrieve its image. The technique recovers the phase lost by detecting the diffraction patterns by using experimentally known constraints, in this case the measured diffraction intensities and the assumed scan positions on the sample. The spatial resolution of the recovered image of the sample is limited by the angular extent over which the diffraction patterns are recorded and how well these constraints are known. Here, we explore how reconstruction quality degrades with uncertainties in the scan positions. We show experimentally that large errors in the assumed scan positions on the sample can be numerically determined and corrected using conjugate gradient descent methods. We also explore in simulations the limits, based on the signal to noise of the diffraction patterns and amount of overlap between adjacent scan positions, of just how large these errors can be and still be rendered tractable by this method.
Directory of Open Access Journals (Sweden)
Jibing Wu
2017-01-01
Full Text Available Clustering analysis is a basic and essential method for mining heterogeneous information networks, which consist of multiple types of objects and rich semantic relations among different object types. Heterogeneous information networks are ubiquitous in the real-world applications, such as bibliographic networks and social media networks. Unfortunately, most existing approaches, such as spectral clustering, are designed to analyze homogeneous information networks, which are composed of only one type of objects and links. Some recent studies focused on heterogeneous information networks and yielded some research fruits, such as RankClus and NetClus. However, they often assumed that the heterogeneous information networks usually follow some simple schemas, such as bityped network schema or star network schema. To overcome the above limitations, we model the heterogeneous information network as a tensor without the restriction of network schema. Then, a tensor CP decomposition method is adapted to formulate the clustering problem in heterogeneous information networks. Further, we develop two stochastic gradient descent algorithms, namely, SGDClus and SOSClus, which lead to effective clustering multityped objects simultaneously. The experimental results on both synthetic datasets and real-world dataset have demonstrated that our proposed clustering framework can model heterogeneous information networks efficiently and outperform state-of-the-art clustering methods.
Estimation of IMU and MARG orientation using a gradient descent algorithm.
Madgwick, Sebastian O H; Harrison, Andrew J L; Vaidyanathan, Andrew
2011-01-01
This paper presents a novel orientation algorithm designed to support a computationally efficient, wearable inertial human motion tracking system for rehabilitation applications. It is applicable to inertial measurement units (IMUs) consisting of tri-axis gyroscopes and accelerometers, and magnetic angular rate and gravity (MARG) sensor arrays that also include tri-axis magnetometers. The MARG implementation incorporates magnetic distortion compensation. The algorithm uses a quaternion representation, allowing accelerometer and magnetometer data to be used in an analytically derived and optimised gradient descent algorithm to compute the direction of the gyroscope measurement error as a quaternion derivative. Performance has been evaluated empirically using a commercially available orientation sensor and reference measurements of orientation obtained using an optical measurement system. Performance was also benchmarked against the propriety Kalman-based algorithm of orientation sensor. Results indicate the algorithm achieves levels of accuracy matching that of the Kalman based algorithm; < 0.8° static RMS error, < 1.7° dynamic RMS error. The implications of the low computational load and ability to operate at small sampling rates significantly reduces the hardware and power necessary for wearable inertial movement tracking, enabling the creation of lightweight, inexpensive systems capable of functioning for extended periods of time. © 2011 IEEE
An online supervised learning method based on gradient descent for spiking neurons.
Xu, Yan; Yang, Jing; Zhong, Shuiming
2017-09-01
The purpose of supervised learning with temporal encoding for spiking neurons is to make the neurons emit a specific spike train encoded by precise firing times of spikes. The gradient-descent-based (GDB) learning methods are widely used and verified in the current research. Although the existing GDB multi-spike learning (or spike sequence learning) methods have good performance, they work in an offline manner and still have some limitations. This paper proposes an online GDB spike sequence learning method for spiking neurons that is based on the online adjustment mechanism of real biological neuron synapses. The method constructs error function and calculates the adjustment of synaptic weights as soon as the neurons emit a spike during their running process. We analyze and synthesize desired and actual output spikes to select appropriate input spikes in the calculation of weight adjustment in this paper. The experimental results show that our method obviously improves learning performance compared with the offline learning manner and has certain advantage on learning accuracy compared with other learning methods. Stronger learning ability determines that the method has large pattern storage capacity. Copyright © 2017 Elsevier Ltd. All rights reserved.
Modified Convolutional Neural Network Based on Dropout and the Stochastic Gradient Descent Optimizer
Directory of Open Access Journals (Sweden)
Jing Yang
2018-03-01
Full Text Available This study proposes a modified convolutional neural network (CNN algorithm that is based on dropout and the stochastic gradient descent (SGD optimizer (MCNN-DS, after analyzing the problems of CNNs in extracting the convolution features, to improve the feature recognition rate and reduce the time-cost of CNNs. The MCNN-DS has a quadratic CNN structure and adopts the rectified linear unit as the activation function to avoid the gradient problem and accelerate convergence. To address the overfitting problem, the algorithm uses an SGD optimizer, which is implemented by inserting a dropout layer into the all-connected and output layers, to minimize cross entropy. This study used the datasets MNIST, HCL2000, and EnglishHand as the benchmark data, analyzed the performance of the SGD optimizer under different learning parameters, and found that the proposed algorithm exhibited good recognition performance when the learning rate was set to [0.05, 0.07]. The performances of WCNN, MLP-CNN, SVM-ELM, and MCNN-DS were compared. Statistical results showed the following: (1 For the benchmark MNIST, the MCNN-DS exhibited a high recognition rate of 99.97%, and the time-cost of the proposed algorithm was merely 21.95% of MLP-CNN, and 10.02% of SVM-ELM; (2 Compared with SVM-ELM, the average improvement in the recognition rate of MCNN-DS was 2.35% for the benchmark HCL2000, and the time-cost of MCNN-DS was only 15.41%; (3 For the EnglishHand test set, the lowest recognition rate of the algorithm was 84.93%, the highest recognition rate was 95.29%, and the average recognition rate was 89.77%.
Stenrup, Michael; Lindh, Roland; Fdez Galván, Ignacio
2015-08-15
A method is proposed to easily reduce the number of energy evaluations required to compute numerical gradients when constraints are imposed on the system, especially in connection with rigid fragment optimization. The method is based on the separation of the coordinate space into a constrained and an unconstrained space, and the numerical differentiation is done exclusively in the unconstrained space. The decrease in the number of energy calculations can be very important if the system is significantly constrained. The performance of the method is tested on systems that can be considered as composed of several rigid groups or molecules, and the results show that the error with respect to conventional optimizations is of the order of the convergence criteria. Comparison with another method designed for rigid fragment optimization proves the present method to be competitive. The proposed method can also be applied to combine numerical and analytical gradients computed at different theory levels, allowing an unconstrained optimization with numerical differentiation restricted to the most significant degrees of freedom. This approach can be a practical alternative when analytical gradients are not available at the desired computational level and full numerical differentiation is not affordable. © 2015 Wiley Periodicals, Inc.
A constrained conjugate gradient algorithm for computed tomography
Energy Technology Data Exchange (ETDEWEB)
Azevedo, S.G.; Goodman, D.M. [Lawrence Livermore National Lab., CA (United States)
1994-11-15
Image reconstruction from projections of x-ray, gamma-ray, protons and other penetrating radiation is a well-known problem in a variety of fields, and is commonly referred to as computed tomography (CT). Various analytical and series expansion methods of reconstruction and been used in the past to provide three-dimensional (3D) views of some interior quantity. The difficulties of these approaches lie in the cases where (a) the number of views attainable is limited, (b) the Poisson (or other) uncertainties are significant, (c) quantifiable knowledge of the object is available, but not implementable, or (d) other limitations of the data exist. We have adapted a novel nonlinear optimization procedure developed at LLNL to address limited-data image reconstruction problems. The technique, known as nonlinear least squares with general constraints or constrained conjugate gradients (CCG), has been successfully applied to a number of signal and image processing problems, and is now of great interest to the image reconstruction community. Previous applications of this algorithm to deconvolution problems and x-ray diffraction images for crystallography have shown the great promise.
Directory of Open Access Journals (Sweden)
Afan Galih Salman
2011-06-01
Full Text Available The artificial neural network (ANN technology in rainfall prediction can be done using the learning approach. The ANN prediction accuracy is measured by the determination coefficient (R2 and root mean square error (RMSE. This research implements Elman’s Recurrent ANN which is heuristically optimized based on el-nino southern oscilation (ENSO variables: wind, southern oscillation index (SOI, sea surface temperatur (SST dan outgoing long wave radiation (OLR to forecast regional monthly rainfall in Bongan Bali. The heuristic learning optimization done is basically a performance development of standard gradient descent learning algorithm into training algorithms: gradient descent momentum and adaptive learning rate. The patterns of input data affect the performance of Recurrent Elman neural network in estimation process. The first data group that is 75% training data and 25% testing data produce the maximum R2 leap 74,6% while the second data group that is 50% training data and 50% testing data produce the maximum R2 leap 49,8%.
Directory of Open Access Journals (Sweden)
Bighnaraj Naik
2016-03-01
Full Text Available While dealing with real world data for classification using ANNs, it is often difficult to determine the optimal ANN classification model with fast convergence. Also, it is laborious to adjust the set of weights of ANNs by using appropriate learning algorithm to obtain better classification accuracy. In this paper, a variant of Harmony Search (HS, called Global-best Harmony Search along with Gradient Descent Learning is used with Functional Link Artificial Neural Network (FLANN for classification task in data mining. The Global-best Harmony Search (GbHS uses the concepts of Particle Swarm Optimization from Swarm Intelligence to improve the qualities of harmonies. The problem solving strategies of Global-best Harmony Search along with searching capabilities of Gradient Descent Search are used to obtain optimal set of weight for FLANN. The proposed method (GbHS-GDL-FLANN is implemented in MATLAB and compared with other alternatives (FLANN, GA based FLANN, PSO based FLANN, HS based FLANN, Improved HS based FLANN, Self Adaptive HS based FLANN, MLP, SVM and FSN. The GbHS-GDL-FLANN is tested on benchmark datasets from UCI Machine Learning repository by using 5-fold cross validation technique. The proposed method is analyzed under null-hypothesis by using Friedman Test, Holm and Hochberg Procedure and Post-Hoc ANOVA Statistical Analysis (Tukey Test & Dunnett Test for statistical analysis and validity of results. Simulation results reveal that the performance of the proposed GbHS-GDL-FLANN is better and statistically significant from other alternatives.
Liu, Mingxue; Dong, Faqin; Zhang, Wei; Nie, Xiaoqin; Sun, Shiyong; Wei, Hongfu; Luo, Lang; Xiang, Sha; Zhang, Gege
2016-08-15
One of the waste disposal principles is decrement. The programmed gradient descent biosorption of strontium ions by Saccaromyces cerevisiae regarding bioremoval and ashing process for decrement were studied in present research. The results indicated that S. cerevisiae cells showed valid biosorption for strontium ions with greater than 90% bioremoval efficiency for high concentration strontium ions under batch culture conditions. The S. cerevisiae cells bioaccumulated approximately 10% of strontium ions in the cytoplasm besides adsorbing 90% strontium ions on cell wall. The programmed gradient descent biosorption presented good performance with a nearly 100% bioremoval ratio for low concentration strontium ions after 3 cycles. The ashing process resulted in a huge volume and weight reduction ratio as well as enrichment for strontium in the ash. XRD results showed that SrSO4 existed in ash. Simulated experiments proved that sulfate could adjust the precipitation of strontium ions. Finally, we proposed a technological flow process that combined the programmed gradient descent biosorption and ashing, which could yield great decrement and allow the supernatant to meet discharge standard. This technological flow process may be beneficial for nuclides and heavy metal disposal treatment in many fields. Copyright © 2016 Elsevier B.V. All rights reserved.
Directory of Open Access Journals (Sweden)
Huiru Zhao
2016-09-01
Full Text Available An important goal of China’s electric power system reform is to create a double-side day-ahead wholesale electricity market in the future, where the suppliers (represented by GenCOs and demanders (represented by DisCOs compete simultaneously with each other in one market. Therefore, modeling and simulating the dynamic bidding process and the equilibrium in the double-side day-ahead electricity market scientifically is not only important to some developed countries, but also to China to provide a bidding decision-making tool to help GenCOs and DisCOs obtain more profits in market competition. Meanwhile, it can also provide an economic analysis tool to help government officials design the proper market mechanisms and policies. The traditional dynamic game model and table-based reinforcement learning algorithm have already been employed in the day-ahead electricity market modeling. However, those models are based on some assumptions, such as taking the probability distribution function of market clearing price (MCP and each rival’s bidding strategy as common knowledge (in dynamic game market models, and assuming the discrete state and action sets of every agent (in table-based reinforcement learning market models, which are no longer applicable in a realistic situation. In this paper, a modified reinforcement learning method, called gradient descent continuous Actor-Critic (GDCAC algorithm was employed in the double-side day-ahead electricity market modeling and simulation. This algorithm can not only get rid of the abovementioned unrealistic assumptions, but also cope with the Markov decision-making process with continuous state and action sets just like the real electricity market. Meanwhile, the time complexity of our proposed model is only O(n. The simulation result of employing the proposed model in the double-side day-ahead electricity market shows the superiority of our approach in terms of participant’s profit or social welfare
A constrained-gradient method to control divergence errors in numerical MHD
Hopkins, Philip F.
2016-10-01
In numerical magnetohydrodynamics (MHD), a major challenge is maintaining nabla \\cdot {B}=0. Constrained transport (CT) schemes achieve this but have been restricted to specific methods. For more general (meshless, moving-mesh, ALE) methods, `divergence-cleaning' schemes reduce the nabla \\cdot {B} errors; however they can still be significant and can lead to systematic errors which converge away slowly. We propose a new constrained gradient (CG) scheme which augments these with a projection step, and can be applied to any numerical scheme with a reconstruction. This iteratively approximates the least-squares minimizing, globally divergence-free reconstruction of the fluid. Unlike `locally divergence free' methods, this actually minimizes the numerically unstable nabla \\cdot {B} terms, without affecting the convergence order of the method. We implement this in the mesh-free code GIZMO and compare various test problems. Compared to cleaning schemes, our CG method reduces the maximum nabla \\cdot {B} errors by ˜1-3 orders of magnitude (˜2-5 dex below typical errors if no nabla \\cdot {B} cleaning is used). By preventing large nabla \\cdot {B} at discontinuities, this eliminates systematic errors at jumps. Our CG results are comparable to CT methods; for practical purposes, the nabla \\cdot {B} errors are eliminated. The cost is modest, ˜30 per cent of the hydro algorithm, and the CG correction can be implemented in a range of numerical MHD methods. While for many problems, we find Dedner-type cleaning schemes are sufficient for good results, we identify a range of problems where using only Powell or `8-wave' cleaning can produce order-of-magnitude errors.
Prato, Marco; Bonettini, Silvia; Loris, Ignace; Porta, Federica; Rebegoldi, Simone
2016-10-01
The scaled gradient projection (SGP) method is a first-order optimization method applicable to the constrained minimization of smooth functions and exploiting a scaling matrix multiplying the gradient and a variable steplength parameter to improve the convergence of the scheme. For a general nonconvex function, the limit points of the sequence generated by SGP have been proved to be stationary, while in the convex case and with some restrictions on the choice of the scaling matrix the sequence itself converges to a constrained minimum point. In this paper we extend these convergence results by showing that the SGP sequence converges to a limit point provided that the objective function satisfies the Kurdyka-Łojasiewicz property at each point of its domain and its gradient is Lipschitz continuous.
Directory of Open Access Journals (Sweden)
Bighnaraj Naik
2018-01-01
Full Text Available All the higher order ANNs (HONNs including functional link ANN (FLANN are sensitive to random initialization of weight and rely on the learning algorithms adopted. Although a selection of efficient learning algorithms for HONNs helps to improve the performance, on the other hand, initialization of weights with optimized weights rather than random weights also play important roles on its efficiency. In this paper, the problem solving approach of the teaching learning based optimization (TLBO along with learning ability of the gradient descent learning (GDL is used to obtain the optimal set of weight of FLANN learning model. TLBO does not require any specific parameters rather it requires only some of the common independent parameters like number of populations, number of iterations and stopping criteria, thereby eliminating the intricacy in selection of algorithmic parameters for adjusting the set of weights of FLANN model. The proposed TLBO-FLANN is implemented in MATLAB and compared with GA-FLANN, PSO-FLANN and HS-FLANN. The TLBO-FLANN is tested on various 5-fold cross validated benchmark data sets from UCI machine learning repository and analyzed under the null-hypothesis by using Friedman test, Holm’s procedure and post hoc ANOVA statistical analysis (Tukey test & Dunnett test.
DEFF Research Database (Denmark)
Sadegh, Payman
1997-01-01
This paper deals with a projection algorithm for stochastic approximation using simultaneous perturbation gradient approximation for optimization under inequality constraints where no direct gradient of the loss function is available and the inequality constraints are given as explicit functions...... of the optimization parameters. It is shown that, under application of the projection algorithm, the parameter iterate converges almost surely to a Kuhn-Tucker point, The procedure is illustrated by a numerical example, (C) 1997 Elsevier Science Ltd....
Directory of Open Access Journals (Sweden)
K. Ramachandran
2012-02-01
Full Text Available Spatial gradients of tomographic velocities are seldom used in interpretation of subsurface fault structures. This study shows that spatial velocity gradients can be used effectively in identifying subsurface discontinuities in the horizontal and vertical directions. Three-dimensional velocity models constructed through tomographic inversion of active source and/or earthquake traveltime data are generally built from an initial 1-D velocity model that varies only with depth. Regularized tomographic inversion algorithms impose constraints on the roughness of the model that help to stabilize the inversion process. Final velocity models obtained from regularized tomographic inversions have smooth three-dimensional structures that are required by the data. Final velocity models are usually analyzed and interpreted either as a perturbation velocity model or as an absolute velocity model. Compared to perturbation velocity model, absolute velocity models have an advantage of providing constraints on lithology. Both velocity models lack the ability to provide sharp constraints on subsurface faults. An interpretational approach utilizing spatial velocity gradients applied to northern Cascadia shows that subsurface faults that are not clearly interpretable from velocity model plots can be identified by sharp contrasts in velocity gradient plots. This interpretation resulted in inferring the locations of the Tacoma, Seattle, Southern Whidbey Island, and Darrington Devil's Mountain faults much more clearly. The Coast Range Boundary fault, previously hypothesized on the basis of sedimentological and tectonic observations, is inferred clearly from the gradient plots. Many of the fault locations imaged from gradient data correlate with earthquake hypocenters, indicating their seismogenic nature.
A feasible DY conjugate gradient method for linear equality constraints
LI, Can
2017-09-01
In this paper, we propose a feasible conjugate gradient method for solving linear equality constrained optimization problem. The method is an extension of the Dai-Yuan conjugate gradient method proposed by Dai and Yuan to linear equality constrained optimization problem. It can be applied to solve large linear equality constrained problem due to lower storage requirement. An attractive property of the method is that the generated direction is always feasible and descent direction. Under mild conditions, the global convergence of the proposed method with exact line search is established. Numerical experiments are also given which show the efficiency of the method.
Fastest Rates for Stochastic Mirror Descent Methods
Hanzely, Filip
2018-03-20
Relative smoothness - a notion introduced by Birnbaum et al. (2011) and rediscovered by Bauschke et al. (2016) and Lu et al. (2016) - generalizes the standard notion of smoothness typically used in the analysis of gradient type methods. In this work we are taking ideas from well studied field of stochastic convex optimization and using them in order to obtain faster algorithms for minimizing relatively smooth functions. We propose and analyze two new algorithms: Relative Randomized Coordinate Descent (relRCD) and Relative Stochastic Gradient Descent (relSGD), both generalizing famous algorithms in the standard smooth setting. The methods we propose can be in fact seen as a particular instances of stochastic mirror descent algorithms. One of them, relRCD corresponds to the first stochastic variant of mirror descent algorithm with linear convergence rate.
Conjugate descent formulation of backpropagation error in ...
African Journals Online (AJOL)
The feedforward neural network architecture uses backpropagation learning to determine optimal weights between dierent interconnected layers. This learning procedure uses a gradient descent technique applied to a sum-of-squares error function for the given input-output pattern. It employs an iterative procedure to ...
Lederer, M.; Magnien, J.; Khatibi, G.; Weiss, B.
2015-04-01
Reliability studies of electronic parts prevalently involve FEM simulations of solder joints under service conditions. However, simulations performed with classical continuum mechanics lead to strain singularities at the surface of material transitions. In consequence, the desired independence of the results from mesh size can usually not be achieved. Therefore, we propose a novel version of strain gradient elasticity which consequently removes strain singularities. Our approach shows similarities to a strain gradient theory which was developed already in the 1960s. But in our version of the theory it is required that the stress tensor of equilibrium states is always symmetric. This approach is implemented in the commercial FEM code ABAQUS through user subroutine UEL. Thus, it is demonstrated that in the new approach mesh convergence is achieved. Furthermore, simulations for solder joints of different sizes predict a mechanical size effect in the sense “smaller is stronger”.
DEFF Research Database (Denmark)
Hutson, John M.; Thorup, Jørgen M.; Beasley, Spencer W.
changes in the management of both congenital and acquired cryptorchidism, such as the widespread use of laparoscopy for impalpable testes inside the abdominal cavity, are fully described. Evidence for the benefits of orchidopexy within the first year of life is reviewed, and an individual chapter is also......This book provides a state of the art overview of all aspects of testicular descent and cryptorchidism, including the mechanisms of descent and the causes, consequences, diagnosis, and treatment of undescended testis. The advances in understanding that have been achieved over the past two decades...
Dictionary descent in optimization
Temlyakov, Vladimir
2015-01-01
The problem of convex optimization is studied. Usually in convex optimization the minimization is over a d-dimensional domain. Very often the convergence rate of an optimization algorithm depends on the dimension d. The algorithms studied in this paper utilize dictionaries instead of a canonical basis used in the coordinate descent algorithms. We show how this approach allows us to reduce dimensionality of the problem. Also, we investigate which properties of a dictionary are beneficial for t...
With precise coordination YE+1 was lowered into the cavern (9-Jan), soon joined by the ?rst barrel wheel YB+2 (19-Jan), then YB+1(4-Feb) and HB+ (13-Feb). The 1920 ton central barrel wheel YB0 rests brie?y on the pit-head cover in anticipation of a monumental descent (28-Feb) that will also trigger an intense campaign of installation of services and detectors underground.
The ﬁrst endcap disc of CMS being lowered slowly and carefully 100 m underground into the experimental cavern. The disc is one of 15 large pieces to make the grand descent. The uniquely shaped slice, 16 m high, about 50 cm thick weighs 400 tonnes. The two HF that were lowered earlier in November can also be seen in the foreground and background.
Complementary curves of descent
Mungan, Carl E.; Lipscombe, Trevor C.
2013-01-01
The shapes of two wires in a vertical plane with the same starting and ending points are described as complementary curves of descent if beads frictionlessly slide down both of them in the same time, starting from rest. Every analytic curve has a unique complement, except for a cycloid (solution of the brachistochrone problem), which is self complementary. A striking example is a straight wire whose complement is a lemniscate of Bernoulli. Alternatively, the wires can be tracks down which round objects undergo a rolling race. The level of presentation is appropriate for an intermediate undergraduate course in classical mechanics.
Lambert, M.; Lesselier, D.; Kooij, B. J.
1998-10-01
The retrieval of an unknown, possibly inhomogeneous, penetrable cylindrical obstacle buried entirely in a known homogeneous half-space - the constitutive material parameters of the obstacle and of its embedding obey a Maxwell model - is considered from single- or multiple-frequency aspect-limited data collected by ideal sensors located in air above the embedding half-space, when a small number of time-harmonic transverse electric (TE)-polarized line sources - the magnetic field H is directed along the axis of the cylinder - is also placed in air. The wavefield is modelled from a rigorous H-field domain integral-differential formulation which involves the dot product of the gradients of the single component of H and of the Green function of the stratified environment times a scalar-valued contrast function which contains the obstacle parameters (the frequency-independent, position-dependent relative permittivity and conductivity). A modified gradient method is developed in order to reconstruct the maps of such parameters within a prescribed search domain from the iterative minimization of a cost functional which incorporates both the error in reproducing the data and the error on the field built inside this domain. Non-physical values are excluded and convergence reached by incorporating in the solution algorithm, from a proper choice of unknowns, the condition that the relative permittivity be larger than or equal to 1, and the conductivity be non-negative. The efficiency of the constrained method is illustrated from noiseless and noisy synthetic data acquired independently. The importance of the choice of the initial values of the sought quantities, the need for a periodic refreshment of the constitutive parameters to avoid the algorithm providing inconsistent results, and the interest of a frequency-hopping strategy to obtain finer and finer features of the obstacle when the frequency is raised, are underlined. It is also shown that though either the permittivity
A New Interpolation Approach for Linearly Constrained Convex Optimization
Espinoza, Francisco
2012-08-01
In this thesis we propose a new class of Linearly Constrained Convex Optimization methods based on the use of a generalization of Shepard\\'s interpolation formula. We prove the properties of the surface such as the interpolation property at the boundary of the feasible region and the convergence of the gradient to the null space of the constraints at the boundary. We explore several descent techniques such as steepest descent, two quasi-Newton methods and the Newton\\'s method. Moreover, we implement in the Matlab language several versions of the method, particularly for the case of Quadratic Programming with bounded variables. Finally, we carry out performance tests against Matab Optimization Toolbox methods for convex optimization and implementations of the standard log-barrier and active-set methods. We conclude that the steepest descent technique seems to be the best choice so far for our method and that it is competitive with other standard methods both in performance and empirical growth order.
Stochastic Spectral Descent for Discrete Graphical Models
International Nuclear Information System (INIS)
Carlson, David; Hsieh, Ya-Ping; Collins, Edo; Carin, Lawrence; Cevher, Volkan
2015-01-01
Interest in deep probabilistic graphical models has in-creased in recent years, due to their state-of-the-art performance on many machine learning applications. Such models are typically trained with the stochastic gradient method, which can take a significant number of iterations to converge. Since the computational cost of gradient estimation is prohibitive even for modestly sized models, training becomes slow and practically usable models are kept small. In this paper we propose a new, largely tuning-free algorithm to address this problem. Our approach derives novel majorization bounds based on the Schatten- norm. Intriguingly, the minimizers of these bounds can be interpreted as gradient methods in a non-Euclidean space. We thus propose using a stochastic gradient method in non-Euclidean space. We both provide simple conditions under which our algorithm is guaranteed to converge, and demonstrate empirically that our algorithm leads to dramatically faster training and improved predictive ability compared to stochastic gradient descent for both directed and undirected graphical models.
Directory of Open Access Journals (Sweden)
Andreea Koreanschi
2017-02-01
Full Text Available In this paper, an ‘in-house’ genetic algorithm is described and applied to an optimization problem for improving the aerodynamic performances of an aircraft wing tip through upper surface morphing. The algorithm’s performances were studied from the convergence point of view, in accordance with design conditions. The algorithm was compared to two other optimization methods, namely the artificial bee colony and a gradient method, for two optimization objectives, and the results of the optimizations with each of the three methods were plotted on response surfaces obtained with the Monte Carlo method, to show that they were situated in the global optimum region. The optimization results for 16 wind tunnel test cases and 2 objective functions were presented. The 16 cases used for the optimizations were included in the experimental test plan for the morphing wing-tip demonstrator, and the results obtained using the displacements given by the optimizations were evaluated.
Knox, C. E.; Vicroy, D. D.; Simmon, D. A.
1985-01-01
A simple, airborne, flight-management descent algorithm was developed and programmed into a small programmable calculator. The algorithm may be operated in either a time mode or speed mode. The time mode was designed to aid the pilot in planning and executing a fuel-conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The speed model was designed for planning fuel-conservative descents when time is not a consideration. The descent path for both modes was calculated for a constant with considerations given for the descent Mach/airspeed schedule, gross weight, wind, wind gradient, and nonstandard temperature effects. Flight tests, using the algorithm on the programmable calculator, showed that the open-loop guidance could be useful to airline flight crews for planning and executing fuel-conservative descents.
Energy Technology Data Exchange (ETDEWEB)
Knox, C.E.; Vicroy, D.D.; Simmon, D.A.
1985-05-01
A simple, airborne, flight-management descent algorithm was developed and programmed into a small programmable calculator. The algorithm may be operated in either a time mode or speed mode. The time mode was designed to aid the pilot in planning and executing a fuel-conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The speed model was designed for planning fuel-conservative descents when time is not a consideration. The descent path for both modes was calculated for a constant with considerations given for the descent Mach/airspeed schedule, gross weight, wind, wind gradient, and nonstandard temperature effects. Flight tests, using the algorithm on the programmable calculator, showed that the open-loop guidance could be useful to airline flight crews for planning and executing fuel-conservative descents.
Luteinizing hormone in testicular descent
DEFF Research Database (Denmark)
Toppari, Jorma; Kaleva, Marko M; Virtanen, Helena E
2007-01-01
alone is not sufficient for normal testicular descent. The regulation of androgen production is influenced both by placental human chorionic gonadotropin (hCG) and pituitary luteinizing hormone (LH). There is evidence that the longer pregnancy continues, the more important role pituitary LH may have...... levels with slightly but significantly elevated LH levels as compared to healthy boys. This high gonadotropin drive may compensate for mild Leydig cell dysfunction in cryptorchidism....
SGDLibrary: A MATLAB library for stochastic gradient descent algorithms
Kasai, Hiroyuki
2017-01-01
We consider the problem of finding the minimizer of a function $f: \\mathbb{R}^d \\rightarrow \\mathbb{R}$ of the form $\\min f(w) = \\frac{1}{n}\\sum_{i}f_i({w})$. This problem has been studied intensively in recent years in machine learning research field. One typical but promising approach for large-scale data is stochastic optimization algorithm. SGDLibrary is a flexible, extensible and efficient pure-Matlab library of a collection of stochastic optimization algorithms. The purpose of the libra...
Mühlherr, Bernhard; Weiss, Richard M
2015-01-01
Descent in Buildings begins with the resolution of a major open question about the local structure of Bruhat-Tits buildings. The authors then put their algebraic solution into a geometric context by developing a general fixed point theory for groups acting on buildings of arbitrary type, giving necessary and sufficient conditions for the residues fixed by a group to form a kind of subbuilding or "form" of the original building. At the center of this theory is the notion of a Tits index, a combinatorial version of the notion of an index in the relative theory of algebraic groups. These results
Steepest descent method implementation on unconstrained optimization problem using C++ program
Napitupulu, H.; Sukono; Mohd, I. Bin; Hidayat, Y.; Supian, S.
2018-03-01
Steepest Descent is known as the simplest gradient method. Recently, many researches are done to obtain the appropriate step size in order to reduce the objective function value progressively. In this paper, the properties of steepest descent method from literatures are reviewed together with advantages and disadvantages of each step size procedure. The development of steepest descent method due to its step size procedure is discussed. In order to test the performance of each step size, we run a steepest descent procedure in C++ program. We implemented it to unconstrained optimization test problem with two variables, then we compare the numerical results of each step size procedure. Based on the numerical experiment, we conclude the general computational features and weaknesses of each procedure in each case of problem.
Optimization algorithm based on densification and dynamic canonical descent
Bousson, K.; Correia, S. D.
2006-07-01
Stochastic methods have gained some popularity in global optimization in that most of them do not assume the cost functions to be differentiable. They have capabilities to avoid being trapped by local optima, and may converge even faster than gradient-based optimization methods on some problems. The present paper proposes an optimization method, which reduces the search space by means of densification curves, coupled with the dynamic canonical descent algorithm. The performances of the new method are shown on several known problems classically used for testing optimization algorithms, and proved to outperform competitive algorithms such as simulated annealing and genetic algorithms.
Random versus Deterministic Descent in RNA Energy Landscape Analysis
Directory of Open Access Journals (Sweden)
Luke Day
2016-01-01
Full Text Available Identifying sets of metastable conformations is a major research topic in RNA energy landscape analysis, and recently several methods have been proposed for finding local minima in landscapes spawned by RNA secondary structures. An important and time-critical component of such methods is steepest, or gradient, descent in attraction basins of local minima. We analyse the speed-up achievable by randomised descent in attraction basins in the context of large sample sets where the size has an order of magnitude in the region of ~106. While the gain for each individual sample might be marginal, the overall run-time improvement can be significant. Moreover, for the two nongradient methods we analysed for partial energy landscapes induced by ten different RNA sequences, we obtained that the number of observed local minima is on average larger by 7.3% and 3.5%, respectively. The run-time improvement is approximately 16.6% and 6.8% on average over the ten partial energy landscapes. For the large sample size we selected for descent procedures, the coverage of local minima is very high up to energy values of the region where the samples were randomly selected from the partial energy landscapes; that is, the difference to the total set of local minima is mainly due to the upper area of the energy landscapes.
Continuous Descent Operations using Energy Principles
De Jong, P.M.A.
2014-01-01
During today’s aircraft descents, Air Traf?c Control (ATC) commands aircraft to descend to specific altitudes and directions to maintain separation and spacing from other aircraft. When the aircraft is instructed to maintain an intermediate descent altitude, it requires engine thrust to maintain
Metal artifact reduction in x-ray computed tomography (CT) by constrained optimization.
Zhang, Xiaomeng; Wang, Jing; Xing, Lei
2011-02-01
The streak artifacts caused by metal implants have long been recognized as a problem that limits various applications of CT imaging. In this work, the authors propose an iterative metal artifact reduction algorithm based on constrained optimization. After the shape and location of metal objects in the image domain is determined automatically by the binary metal identification algorithm and the segmentation of "metal shadows" in projection domain is done, constrained optimization is used for image reconstruction. It minimizes a predefined function that reflects a priori knowledge of the image, subject to the constraint that the estimated projection data are within a specified tolerance of the available metal-shadow-excluded projection data, with image non-negativity enforced. The minimization problem is solved through the alternation of projection-onto-convex-sets and the steepest gradient descent of the objective function. The constrained optimization algorithm is evaluated with a penalized smoothness objective. The study shows that the proposed method is capable of significantly reducing metal artifacts, suppressing noise, and improving soft-tissue visibility. It outperforms the FBP-type methods and ART and EM methods and yields artifacts-free images. Constrained optimization is an effective way to deal with CT reconstruction with embedded metal objects. Although the method is presented in the context of metal artifacts, it is applicable to general "missing data" image reconstruction problems.
Sobolev gradients and differential equations
Neuberger, J W
2010-01-01
A Sobolev gradient of a real-valued functional on a Hilbert space is a gradient of that functional taken relative to an underlying Sobolev norm. This book shows how descent methods using such gradients allow a unified treatment of a wide variety of problems in differential equations. For discrete versions of partial differential equations, corresponding Sobolev gradients are seen to be vastly more efficient than ordinary gradients. In fact, descent methods with these gradients generally scale linearly with the number of grid points, in sharp contrast with the use of ordinary gradients. Aside from the first edition of this work, this is the only known account of Sobolev gradients in book form. Most of the applications in this book have emerged since the first edition was published some twelve years ago. What remains of the first edition has been extensively revised. There are a number of plots of results from calculations and a sample MatLab code is included for a simple problem. Those working through a fair p...
Propulsive Descent Technologies (PDT): Original Content Project
National Aeronautics and Space Administration — Future missions to Mars require landed mass that exceeds the capability of current entry, descent, and landing technology. New technology and techniques are...
Terminal Descent Lidar System, Phase I
National Aeronautics and Space Administration — A laser based terminal descent sensor is proposed that will provide real-time ground-relative altitude, attitude, and vertical velocity at high data rates to a...
Steepest descent approximations for accretive operator equations
International Nuclear Information System (INIS)
Chidume, C.E.
1993-03-01
A necessary and sufficient condition is established for the strong convergence of the steepest descent approximation to a solution of equations involving quasi-accretive operators defined on a uniformly smooth Banach space. (author). 49 refs
Stochastic Optimal Control for Powered Descent Guidance
National Aeronautics and Space Administration — Entry, descent, and landing (EDL) is the process of a spacecraft entering a planet's atmosphere, decelerating from orbit, and descending to a safe landing on the...
Bounding Regions to Plane Steepest Descent Curves of Quasiconvex Families
Directory of Open Access Journals (Sweden)
Marco Longinetti
2016-01-01
Full Text Available Two-dimensional steepest descent curves (SDC for a quasiconvex family are considered; the problem of their extensions (with constraints outside of a convex body K is studied. It is shown that possible extensions are constrained to lie inside of suitable bounding regions depending on K. These regions are bounded by arcs of involutes of ∂K and satisfy many inclusions properties. The involutes of the boundary of an arbitrary plane convex body are defined and written by their support function. Extensions SDC of minimal length are constructed. Self-contracting sets (with opposite orientation are considered: necessary and/or sufficient conditions for them to be subsets of SDC are proved.
Sparse Nonlinear Electromagnetic Imaging Accelerated With Projected Steepest Descent Algorithm
Desmal, Abdulla
2017-04-03
An efficient electromagnetic inversion scheme for imaging sparse 3-D domains is proposed. The scheme achieves its efficiency and accuracy by integrating two concepts. First, the nonlinear optimization problem is constrained using L₀ or L₁-norm of the solution as the penalty term to alleviate the ill-posedness of the inverse problem. The resulting Tikhonov minimization problem is solved using nonlinear Landweber iterations (NLW). Second, the efficiency of the NLW is significantly increased using a steepest descent algorithm. The algorithm uses a projection operator to enforce the sparsity constraint by thresholding the solution at every iteration. Thresholding level and iteration step are selected carefully to increase the efficiency without sacrificing the convergence of the algorithm. Numerical results demonstrate the efficiency and accuracy of the proposed imaging scheme in reconstructing sparse 3-D dielectric profiles.
Descent among the Wayú. Concepts and social meanings
Mancuso, Alessandro
2014-01-01
Descent among the Wayú. Concepts and social meanings. Taking the contemporary rethinking of the descent notion in Lowland South American ethnography as a starting point, the article provides an analysis of matrilineal descent among the Wayú. Using new ethnographical data, special attention is paid to indigenous concepts and to the way matrilineal descent articulates with other principles of social classification. By virtue of the role that matrilineal descent plays in defining territoriality ...
Luo, Biao; Liu, Derong; Wu, Huai-Ning
2017-10-03
Reinforcement learning has proved to be a powerful tool to solve optimal control problems over the past few years. However, the data-based constrained optimal control problem of nonaffine nonlinear discrete-time systems has rarely been studied yet. To solve this problem, an adaptive optimal control approach is developed by using the value iteration-based Q-learning (VIQL) with the critic-only structure. Most of the existing constrained control methods require the use of a certain performance index and only suit for linear or affine nonlinear systems, which is unreasonable in practice. To overcome this problem, the system transformation is first introduced with the general performance index. Then, the constrained optimal control problem is converted to an unconstrained optimal control problem. By introducing the action-state value function, i.e., Q-function, the VIQL algorithm is proposed to learn the optimal Q-function of the data-based unconstrained optimal control problem. The convergence results of the VIQL algorithm are established with an easy-to-realize initial condition Q(0)(x,a)≽ 0. To implement the VIQL algorithm, the critic-only structure is developed, where only one neural network is required to approximate the Q-function. The converged Q-function obtained from the critic-only VIQL method is employed to design the adaptive constrained optimal controller based on the gradient descent scheme. Finally, the effectiveness of the developed adaptive control method is tested on three examples with computer simulation.
Adaptive Regularization of Neural Networks Using Conjugate Gradient
DEFF Research Database (Denmark)
Goutte, Cyril; Larsen, Jan
1998-01-01
Andersen et al. (1997) and Larsen et al. (1996, 1997) suggested a regularization scheme which iteratively adapts regularization parameters by minimizing validation error using simple gradient descent. In this contribution we present an improved algorithm based on the conjugate gradient technique........ Numerical experiments with feedforward neural networks successfully demonstrate improved generalization ability and lower computational cost...
Descent principle in modular Galois theory
Indian Academy of Sciences (India)
Springer Verlag Heidelberg #4 2048 1996 Dec 15 10:16:45
E-mail: ram@cs.purdue.edu; keskar@math.unipune.ernet.in. MS received 24 July 2000; revised 1 December 2000. Abstract. We propound a descent principle by which previously constructed equa- tions over GF(qn)(X) may be deformed to have incarnations over GF(q)(X) without changing their Galois groups. Currently this ...
America's Descent into Madness
Giroux, Henry A.
2014-01-01
This article describes America's descent into madness under the regime of neoliberalism that has emerged in the United States since the late 1970s. In part, this is due to the emergence of a public pedagogy produced by the corporate-owned media that now saturates Americans with a market-driven value system that undermines those formative…
Minimizing convex functions by continuous descent methods
Directory of Open Access Journals (Sweden)
Sergiu Aizicovici
2010-01-01
Full Text Available We study continuous descent methods for minimizing convex functions, defined on general Banach spaces, which are associated with an appropriate complete metric space of vector fields. We show that there exists an everywhere dense open set in this space of vector fields such that each of its elements generates strongly convergent trajectories.
Large Airborne Full Tensor Gradient Data Inversion Based on a Non-Monotone Gradient Method
Sun, Yong; Meng, Zhaohai; Li, Fengting
2018-03-01
Following the development of gravity gradiometer instrument technology, the full tensor gravity (FTG) data can be acquired on airborne and marine platforms. Large-scale geophysical data can be obtained using these methods, making such data sets a number of the "big data" category. Therefore, a fast and effective inversion method is developed to solve the large-scale FTG data inversion problem. Many algorithms are available to accelerate the FTG data inversion, such as conjugate gradient method. However, the conventional conjugate gradient method takes a long time to complete data processing. Thus, a fast and effective iterative algorithm is necessary to improve the utilization of FTG data. Generally, inversion processing is formulated by incorporating regularizing constraints, followed by the introduction of a non-monotone gradient-descent method to accelerate the convergence rate of FTG data inversion. Compared with the conventional gradient method, the steepest descent gradient algorithm, and the conjugate gradient algorithm, there are clear advantages of the non-monotone iterative gradient-descent algorithm. Simulated and field FTG data were applied to show the application value of this new fast inversion method.
Sharp spatially constrained inversion
DEFF Research Database (Denmark)
Vignoli, Giulio G.; Fiandaca, Gianluca G.; Christiansen, Anders Vest C A.V.C.
2013-01-01
We present sharp reconstruction of multi-layer models using a spatially constrained inversion with minimum gradient support regularization. In particular, its application to airborne electromagnetic data is discussed. Airborne surveys produce extremely large datasets, traditionally inverted...... by using smoothly varying 1D models. Smoothness is a result of the regularization constraints applied to address the inversion ill-posedness. The standard Occam-type regularized multi-layer inversion produces results where boundaries between layers are smeared. The sharp regularization overcomes...... inversions are compared against classical smooth results and available boreholes. With the focusing approach, the obtained blocky results agree with the underlying geology and allow for easier interpretation by the end-user....
Three-dimensional sparse electromagnetic imaging accelerated by projected steepest descent
Desmal, Abdulla
2016-11-02
An efficient and accurate scheme for solving the nonlinear electromagnetic inverse scattering problem on three-dimensional sparse investigation domains is proposed. The minimization problem is constructed in such a way that the data misfit between measurements and scattered fields (which are expressed as a nonlinear function of the contrast) is constrained by the contrast\\'s first norm. The resulting minimization problem is solved using nonlinear Landweber iterations accelerated using a steepest descent algorithm. A projection operator is applied at every iteration to enforce the sparsity constraint by thresholding the result of that iteration. Steepest descent algorithm ensures accelerated and convergent solution by utilizing larger iteration steps selected based on a necessary B-condition.
Frequency domain full-waveform inversion with nonlinear descent directions
Geng, Yu; Pan, Wenyong; Innanen, Kristopher A.
2018-01-01
Full waveform inversion (FWI) is a highly nonlinear inverse problem, normally solved iteratively, with each iteration involving an update constructed through linear operations on the residuals. Incorporating a flexible degree of nonlinearity within each update may have important consequences for convergence rates, determination of low model wavenumbers, and discrimination of parameters. We examine one approach for doing so, wherein higher-order scattering terms are included within the sensitivity kernel during the construction of the descent direction, adjusting it away from that of the standard Gauss-Newton approach. These scattering terms are naturally admitted when we construct the sensitivity kernel by varying not the current but the to-be-updated model at each iteration. Linear and/or nonlinear inverse scattering methodologies allow these additional sensitivity contributions to be computed from the current data residuals within any given update. We show that in the presence of pre-critical reflection data, the error in a second-order nonlinear update to a background of s0 is, in our scheme, proportional to at most (Δs/s0)3 in the actual parameter jump Δs causing the reflection. In contrast, the error in a standard Gauss-Newton FWI update is proportional to (Δs/s0)2. For numerical implementation of more complex cases, we introduce a nonlinear frequency-domain scheme, with an inner and an outer loop. A perturbation is determined from the data residuals within the inner loop, and a descent direction based on the resulting nonlinear sensitivity kernel is computed in the outer loop. We examine the response of this nonlinear FWI using acoustic single-parameter synthetics derived from the Marmousi model. The inverted results vary depending on data frequency ranges and initial models, but we conclude that the nonlinear FWI has the capability to generate high resolution model estimates in both shallow and deep regions, and to converge rapidly, relative to a
Using Effective Media Theory to Better Constrain Seismic Full Waveform Inversion
Afanasiev, M.; Fichtner, A.; Boehm, C.
2015-12-01
In seismology, effective media theory exploits the fact that bandlimited elastic waves are sensitive to small-scale heterogeneity in only an 'effective' manner. From effective media theories follow modern homogenization techniques, which seek to upscale a fine-scale medium into an effective medium that produces an identical long-period solution to the elastic wave equation. These techniques are currently finding heavy use in seismic waveform modelling, which has immediate applications to seismic full waveform inversion (FWI). FWI is usually formulated as a non-linear gradient-based inverse problem. As with most problems of this class, the solution is strongly dependent on the starting model: if a given starting model predicts 'cycle-skipped' synthetic data, the method is unlikely to converge to the global minimum. As low frequencies are less prone to this 'cycle-skipping', the issue is commonly solved by following a multi-scale approach. While this is often successful, it requires that each new frequency band satisfies the half-cycle criterion before being used. We propose to use effective media theory as a communicator between scales and frequency bands; to allow us to broaden the investigated frequency band earlier in the inversion workflow. To accomplish this, we take advantage of the intuitive notion that the homogenized gradient should vanish at scales much larger than that probed by waves within a given frequency band. Practically, this involves first calculating a broadband waveform sensitivity. Then, within a narrow frequency band which includes the lowest frequency data, we calculate the gradient with respect to a modified misfit function. This modification comes in the form of a Lagrange multiplier constraint which forces the homogenized gradient to zero. Then, we cascade upwards through frequencies, adding constraints which enforce the homogenized gradient in any frequency band to equal the constrained gradient at the next lowest frequency band. By
Noise annoyance caused by continuous descent approaches compared to regular descent procedures
White, Kim; Arntzen, Michael; Walker, Francesco; Waiyaki, Fredrick M.; Meeter, Martijn; Bronkhorst, Adelbert W.
2017-01-01
During Continuous Descent Approaches (CDAs) aircraft glide towards the runway resulting in reduced noise and fuel usage. Here, we investigated whether such landings cause less noise annoyance than a regular stepwise approach. Both landing types were compared in a controlled laboratory setting with a
Approximate error conjugation gradient minimization methods
Kallman, Jeffrey S
2013-05-21
In one embodiment, a method includes selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, calculating an approximate error using the subset of rays, and calculating a minimum in a conjugate gradient direction based on the approximate error. In another embodiment, a system includes a processor for executing logic, logic for selecting a subset of rays from a set of all rays to use in an error calculation for a constrained conjugate gradient minimization problem, logic for calculating an approximate error using the subset of rays, and logic for calculating a minimum in a conjugate gradient direction based on the approximate error. In other embodiments, computer program products, methods, and systems are described capable of using approximate error in constrained conjugate gradient minimization problems.
Development and descent of the testis in relation to cryptorchidism
DEFF Research Database (Denmark)
Virtanen, Helena E; Cortes, Dina; Rajpert-De Meyts, Ewa
2007-01-01
The testis descends in two phases. Animal studies suggest, that the transabdominal descent of the testis depends on the insulin-like hormone 3 (INSL3). Androgens are important in the inguinoscrotal testicular descent in animals and humans. In general, the cause of cryptorchidism is unknown...... and the aetiology is possibly multifactorial. Histological changes in cryptorchid testes demonstrate disturbed development. Conclusion: Since testicular descent is regulated by testis-derived hormones, cryptorchidism may reflect a functional defect of the testis....
The grand descent has begun for CMS
2006-01-01
Until recently, the CMS experimental cavern looked relatively empty; its detector was assembled entirely at ground level, to be lowered underground in 15 sections. On 2 November, the first hadronic forward calorimeter led the way with a grand descent. The first section of the CMS detector (centre of photo) arriving from the vertical shaft, viewed from the cavern floor. There is something unusual about the construction of the CMS detector. Instead of being built in the experimental cavern, like all the other detectors in the LHC experiments, it was constructed at ground level. This was to allow for easy access during the assembly of the detector and to minimise the size of the excavated cavern. The slightly nerve-wracking task of lowering it safely into the cavern in separate sections came after the complete detector was successfully tested with a magnetic field at ground level. In the early morning of 2 November, the first section of the CMS detector began its eagerly awaited descent into the underground ca...
Gastroscopy in immigrants of Turkish descent.
Wegman, Anna-Isthar; Loffeld, Ruud Jlf
2009-07-01
Little data is known on morbidity and Helicobacter pylori in the upper part of the gastrointestinal tract in male and female patients of Turkish descent. A study was done in order to assess the presence of H. pylori in Turkish men and women in relation to the diagnostic yield of the endoscopy. All consecutive patients of Turkish descent were included in the present study. Detection of H. pylori was done with hematoxylin-eosin stain, an immunoperoxidase and Gram stain and culture. In 16 years, 2427 procedures (10.4%) were done in Turkish patients. After exclusions, 842 endoscopies in Turkish women and 827 procedures in Turkish men remained. Peptic ulcer disease was diagnosed in 101 (6%) patients and reflux esophagitis in 97 patients (5.8%). Seven patients had cancer. In 749 patients (64%), no macroscopic abnormalities were seen. Turkish men suffered more often from reflux esophagitis (81% vs 19%, P peptic ulcer disease (74% vs 26%, P peptic ulcer disease in women, while the peptic ulcers decreased, and reflux esophagitis increased in men. Men were significantly more often H. pylori-positive (P = 0.03). There was a clear trend towards a decrease in H. pylori-positives. There are differences in the presence of ulcer disease and reflux esophagitis between Turkish men and women. Men are significantly more often H. pylori-positive. Prevalence of H. pylori infection in Turkish patients slowly decreases in the consecutive years in both men and women.
A Globally Convergent Parallel SSLE Algorithm for Inequality Constrained Optimization
Directory of Open Access Journals (Sweden)
Zhijun Luo
2014-01-01
Full Text Available A new parallel variable distribution algorithm based on interior point SSLE algorithm is proposed for solving inequality constrained optimization problems under the condition that the constraints are block-separable by the technology of sequential system of linear equation. Each iteration of this algorithm only needs to solve three systems of linear equations with the same coefficient matrix to obtain the descent direction. Furthermore, under certain conditions, the global convergence is achieved.
Stochastic Spectral and Conjugate Descent Methods
Kovalev, Dmitry
2018-02-11
The state-of-the-art methods for solving optimization problems in big dimensions are variants of randomized coordinate descent (RCD). In this paper we introduce a fundamentally new type of acceleration strategy for RCD based on the augmentation of the set of coordinate directions by a few spectral or conjugate directions. As we increase the number of extra directions to be sampled from, the rate of the method improves, and interpolates between the linear rate of RCD and a linear rate independent of the condition number. We develop and analyze also inexact variants of these methods where the spectral and conjugate directions are allowed to be approximate only. We motivate the above development by proving several negative results which highlight the limitations of RCD with importance sampling.
Distributed Control by Lagrangian Steepest Descent
Wolpert, David H.; Bieniawski, Stefan
2004-01-01
Often adaptive, distributed control can be viewed as an iterated game between independent players. The coupling between the players mixed strategies, arising as the system evolves from one instant to the next, is determined by the system designer. Information theory tells us that the most likely joint strategy of the players, given a value of the expectation of the overall control objective function, is the minimizer of a function o the joint strategy. So the goal of the system designer is to speed evolution of the joint strategy to that Lagrangian mhimbhgpoint,lowerthe expectated value of the control objective function, and repeat Here we elaborate the theory of algorithms that do this using local descent procedures, and that thereby achieve efficient, adaptive, distributed control.
Planetary entry, descent, and landing technologies
Pichkhadze, K.; Vorontsov, V.; Polyakov, A.; Ivankov, A.; Taalas, P.; Pellinen, R.; Harri, A.-M.; Linkin, V.
2003-04-01
Martian meteorological lander (MML) is intended for landing on the Martian surface in order to monitor the atmosphere at landing point for one Martian year. MMLs shall become the basic elements of a global network of meteorological mini-landers, observing the dynamics of changes of the atmospheric parameters on the Red Planet. The MML main scientific tasks are as follows: (1) Study of vertical structure of the Martian atmosphere throughout the MML descent; (2) On-surface meteorological observations for one Martian year. One of the essential factors influencing the lander's design is its entry, descent, and landing (EDL) sequence. During Phase A of the MML development, five different options for the lander's design were carefully analyzed. All of these options ensure the accomplishment of the above-mentioned scientific tasks with high effectiveness. CONCEPT A (conventional approach): Two lander options (with a parachute system + airbag and an inflatable airbrake + airbag) were analyzed. They are similar in terms of fulfilling braking phases and completely analogous in landing by means of airbags. CONCEPT B (innovative approach): Three lander options were analyzed. The distinguishing feature is the presence of inflatable braking units (IBU) in their configurations. SELECTED OPTION (innovative approach): Incorporating a unique design approach and modern technologies, the selected option of the lander represents a combination of the options analyzed in the framework of Concept B study. Currently, the selected lander option undergoes systems testing (Phase D1). Several MMLs can be delivered to Mars in frameworks of various missions as primary or piggybacking payload: (1) USA-led "Mars Scout" (2007); (2) France-led "NetLander" (2007/2009); (3) Russia-led "Mars-Deimos-Phobos sample return" (2007); (4) Independent mission (currently under preliminary study); etc.
Enumerating set partitions according to the number of descents of ...
Indian Academy of Sciences (India)
) according to the number of descents of size or more, where ≥ 1 is fixed. An explicit expression in terms of Stirling numbers of the second kind may be given for the total number of such descents in all the members of (,). We also ...
43 CFR 10.14 - Lineal descent and cultural affiliation.
2010-10-01
... evidence sufficient to: (i) Establish the identity and cultural characteristics of the earlier group, (ii... 43 Public Lands: Interior 1 2010-10-01 2010-10-01 false Lineal descent and cultural affiliation... GRAVES PROTECTION AND REPATRIATION REGULATIONS General § 10.14 Lineal descent and cultural affiliation...
A discretized algorithm for the solution of a constrained, continuous ...
African Journals Online (AJOL)
A discretized algorithm for the solution of a constrained, continuous quadratic control problem. ... Numerical solution techniques such as Function space algorithm (FSA), Extended conjugate gradient method (ECGM) and Imbedding extended conjugate gradient method (MECGM) are common techniques for solving optimal ...
High resolution quantitative phase imaging of live cells with constrained optimization approach
Pandiyan, Vimal Prabhu; Khare, Kedar; John, Renu
2016-03-01
Quantitative phase imaging (QPI) aims at studying weakly scattering and absorbing biological specimens with subwavelength accuracy without any external staining mechanisms. Use of a reference beam at an angle is one of the necessary criteria for recording of high resolution holograms in most of the interferometric methods used for quantitative phase imaging. The spatial separation of the dc and twin images is decided by the reference beam angle and Fourier-filtered reconstructed image will have a very poor resolution if hologram is recorded below a minimum reference angle condition. However, it is always inconvenient to have a large reference beam angle while performing high resolution microscopy of live cells and biological specimens with nanometric features. In this paper, we treat reconstruction of digital holographic microscopy images as a constrained optimization problem with smoothness constraint in order to recover only complex object field in hologram plane even with overlapping dc and twin image terms. We solve this optimization problem by gradient descent approach iteratively and the smoothness constraint is implemented by spatial averaging with appropriate size. This approach will give excellent high resolution image recovery compared to Fourier filtering while keeping a very small reference angle. We demonstrate this approach on digital holographic microscopy of live cells by recovering the quantitative phase of live cells from a hologram recorded with nearly zero reference angle.
in a Family of South Indian Descent
Directory of Open Access Journals (Sweden)
Muthiah Subramanian
2015-01-01
Full Text Available Inherited channelopathies are a heterogeneous group of disorders resulting from dysfunction of ion channels in cellular membranes. They may manifest as diseases affecting skeletal muscle contraction, the conduction system of the heart, nervous system function, and vision syndromes. We describe a family of South Indian descent with hypokalemic periodic paralysis in which four members also have idiopathic generalized epilepsy. Hypokalemic periodic paralysis is a genetically heterogeneous channelopathy that has been linked to mutations in genes encoding three ion channels CACNIAS, SCN4A, and KCNJ2 predominantly. Although data on specific gene in idiopathic generalized epilepsy is relatively scarce, mutations of voltage gated sodium channel subunit genes (CACNB4 and nonsense mutations in voltage gated calcium channels (CACNA1A have been linked to idiopathic generalized epilepsy in two families. We speculate that gene mutations altering the ability of the beta subunit to interact with the alpha subunit of the CaV1.1 channel and mutations in the pore-forming potassium channel subunit may be possible explanations for the combined manifestation of both diseases. Functional analysis of voltage gated calcium channel and other ion channels mutations may provide additional support and insight for the causal role of these mutations. The understanding of mutations in ion-channel genes will lead to improved diagnosis and treatment of such inherited channelopathies.
Design and Development of the MSL Descent Stage Propulsion System
Weiss, Jeffrey M.; Guernsey, Carl S.
2013-01-01
On August 5, 2012, The Mars Science Laboratory mission successfully landed the largest interplanetary rover ever built, Curiosity, on the surface of Mars. The Entry, Descent, and Landing (EDL) phase of this mission was by far the most complex landing ever attempted on a planetary body. The Descent Stage Propulsion System played an integral and critical role during Curiosity's EDL. The Descent Stage Propulsion System was a one of a kind hydrazine propulsion system designed specifically for the EDL phase of the MSL mission. It was designed, built, and tested at the Jet Propulsion Laboratory (JPL). The purpose of this paper is to present an overview of the design and development of the MSL Descent Stage Propulsion System. Driving requirements, system design, component selection, operational sequence of the system at Mars, new developments, and key challenges will be discussed.
A unified framework of descent algorithms for nonlinear programs and variational inequalities
International Nuclear Information System (INIS)
Patriksson, M.
1993-01-01
We present a framework of algorithms for the solution of continuous optimization and variational inequality problems. In the general algorithm, a search direction finding auxiliary problems is obtained by replacing the original cost function with an approximating monotone cost function. The proposed framework encompasses algorithm classes presented earlier by Cohen, Dafermos, Migdalas, and Tseng, and includes numerous descent and successive approximation type methods, such as Newton methods, Jacobi and Gauss-Siedel type decomposition methods for problems defined over Cartesian product sets, and proximal point methods, among others. The auxiliary problem of the general algorithm also induces equivalent optimization reformulation and descent methods for asymmetric variational inequalities. We study the convergence properties of the general algorithm when applied to unconstrained optimization, nondifferentiable optimization, constrained differentiable optimization, and variational inequalities; the emphasis of the convergence analyses is placed on basic convergence results, convergence using different line search strategies and truncated subproblem solutions, and convergence rate results. This analysis offer a unification of known results; moreover, it provides strengthenings of convergence results for many existing algorithms, and indicates possible improvements of their realizations. 482 refs
Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo
Directory of Open Access Journals (Sweden)
N. Christakis
2009-03-01
Full Text Available Sporadic E layers (E_{s} follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR measurements are analyzed. These were made at Arecibo (Geog. Lat. ~18° N; Magnetic Dip ~50° over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1 tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic E_{s} layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1 a daytime layer starting at ~130 km around midday and descending down to 105 km by local midnight, and 2 a less frequent and weaker nighttime layer which starts prior to midnight at ~130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.
Axial block coordinate descent (ABCD) algorithm for X-ray CT image reconstruction
International Nuclear Information System (INIS)
Fessler, Jeffrey A.; Kim, Donghwan
2011-01-01
The primary drawback of statistical image reconstruction methods for X-ray CT is the computation time required by iterative algorithms. Iterative coordinate descent (ICD) algorithms converge in relatively few iterations but are challenging to parallelize due to their sequential updates. Conjugate gradient (CG) methods and ordered-subsets (OS) algorithms update all pixels simultaneously, which facilitates parallelization, but these algorithms require many more iterations to converge than ICD. This paper proposes a block coordinate descent algorithm for helical and axial cone-beam X-ray CT image reconstruction in which a group of voxels are updated simultaneously. We focus on updating all the voxels within one axial 'column' of the 3D image simultaneously, so we refer to this approach as the axial block coordinate descent (ABCD) algorithm. Because this approach updates many voxels simultaneously (e.g., 64 in an axial scan and hundreds in a helical scan), it is reasonably well suited to parallel processing. At the same time, because the voxels within an axial column are relatively weakly coupled, which is why we selected axial blocks, the algorithm converges fairly quickly. In particular, the simultaneous update of one axial column requires inverting a banded matrix which can be done quickly (ABCD-BAND). An alternative version of the algorithm uses a simpler separable quadratic surrogate for the axial block (ABCD-SQS). Preliminary simulation results illustrate that the ABCD algorithms decrease a regularized weighted least-squares cost function much faster than a traditional separable quadratic surrogate (SQS) method that updates all pixels simultaneously. The proposed ABCD algorithms exhibit about the same decrease per iteration as the ICD method, while appearing much more amenable to parallelization. (orig.)
Seasonal variability and descent of mid-latitude sporadic E layers at Arecibo
Directory of Open Access Journals (Sweden)
N. Christakis
2009-03-01
Full Text Available Sporadic E layers (Es follow regular daily patterns in variability and altitude descent, which are determined primarily by the vertical tidal wind shears in the lower thermosphere. In the present study a large set of sporadic E layer incoherent scatter radar (ISR measurements are analyzed. These were made at Arecibo (Geog. Lat. ~18° N; Magnetic Dip ~50° over many years with ISR runs lasting from several hours to several days, covering evenly all seasons. A new methodology is applied, in which both weak and strong layers are clearly traced by using the vertical electron density gradient as a function of altitude and time. Taking a time base equal to the 24-h local day, statistics were obtained on the seasonal behavior of the diurnal and semidiurnal tidal variability and altitude descent patterns of sporadic E at Arecibo. The diurnal tide, most likely the S(1,1 tide with a vertical wavelength around 25 km, controls fully the formation and descent of the metallic Es layers at low altitudes below 110 km. At higher altitudes, there are two prevailing layers formed presumably by vertical wind shears associated mainly with semidiurnal tides. These include: 1 a daytime layer starting at ~130 km around midday and descending down to 105 km by local midnight, and 2 a less frequent and weaker nighttime layer which starts prior to midnight at ~130 km, descending downwards at somewhat faster rate to reach 110 km by sunrise. The diurnal and semidiurnal-like pattern prevails, with some differences, in all seasons. The differences in occurrence, strength and descending speeds between the daytime and nighttime upper layers are not well understood from the present data alone and require further study.
Design of automation tools for management of descent traffic
Erzberger, Heinz; Nedell, William
1988-01-01
The design of an automated air traffic control system based on a hierarchy of advisory tools for controllers is described. Compatibility of the tools with the human controller, a key objective of the design, is achieved by a judicious selection of tasks to be automated and careful attention to the design of the controller system interface. The design comprises three interconnected subsystems referred to as the Traffic Management Advisor, the Descent Advisor, and the Final Approach Spacing Tool. Each of these subsystems provides a collection of tools for specific controller positions and tasks. This paper focuses primarily on the Descent Advisor which provides automation tools for managing descent traffic. The algorithms, automation modes, and graphical interfaces incorporated in the design are described. Information generated by the Descent Advisor tools is integrated into a plan view traffic display consisting of a high-resolution color monitor. Estimated arrival times of aircraft are presented graphically on a time line, which is also used interactively in combination with a mouse input device to select and schedule arrival times. Other graphical markers indicate the location of the fuel-optimum top-of-descent point and the predicted separation distances of aircraft at a designated time-control point. Computer generated advisories provide speed and descent clearances which the controller can issue to aircraft to help them arrive at the feeder gate at the scheduled times or with specified separation distances. Two types of horizontal guidance modes, selectable by the controller, provide markers for managing the horizontal flightpaths of aircraft under various conditions. The entire system consisting of descent advisor algorithm, a library of aircraft performance models, national airspace system data bases, and interactive display software has been implemented on a workstation made by Sun Microsystems, Inc. It is planned to use this configuration in operational
International Nuclear Information System (INIS)
Ward, G.J.; Heckbert, P.S.; Technische Hogeschool Delft
1992-04-01
A new method for improving the accuracy of a diffuse interreflection calculation is introduced in a ray tracing context. The information from a hemispherical sampling of the luminous environment is interpreted in a new way to predict the change in irradiance as a function of position and surface orientation. The additional computation involved is modest and the benefit is substantial. An improved interpolation of irradiance resulting from the gradient calculation produces smoother, more accurate renderings. This result is achieved through better utilization of ray samples rather than additional samples or alternate sampling strategies. Thus, the technique is applicable to a variety of global illumination algorithms that use hemicubes or Monte Carlo sampling techniques
Evolutionary constrained optimization
Deb, Kalyanmoy
2015-01-01
This book makes available a self-contained collection of modern research addressing the general constrained optimization problems using evolutionary algorithms. Broadly the topics covered include constraint handling for single and multi-objective optimizations; penalty function based methodology; multi-objective based methodology; new constraint handling mechanism; hybrid methodology; scaling issues in constrained optimization; design of scalable test problems; parameter adaptation in constrained optimization; handling of integer, discrete and mix variables in addition to continuous variables; application of constraint handling techniques to real-world problems; and constrained optimization in dynamic environment. There is also a separate chapter on hybrid optimization, which is gaining lots of popularity nowadays due to its capability of bridging the gap between evolutionary and classical optimization. The material in the book is useful to researchers, novice, and experts alike. The book will also be useful...
de Klerk, Etienne; Glineur, François; Taylor, Adrien B.
2016-01-01
We consider the gradient (or steepest) descent method with exact line search applied to a strongly convex function with Lipschitz continuous gradient. We establish the exact worst-case rate of convergence of this scheme, and show that this worst-case behavior is exhibited by a certain convex quadratic function. We also give the tight worst-case complexity bound for a noisy variant of gradient descent method, where exact line-search is performed in a search direction that differs from negative...
de Klerk, Etienne; Glineur, Francois; Taylor, Adrien
2016-01-01
We consider the gradient (or steepest) descent method with exact line search applied to a strongly convex function with Lipschitz continuous gradient. We establish the exact worst-case rate of convergence of this scheme, and show that this worst-case behavior is exhibited by a certain convex
de Klerk, Etienne; Glineur, Francois; Taylor, Adrien
2017-01-01
We consider the gradient (or steepest) descent method with exact line search applied to a strongly convex function with Lipschitz continuous gradient. We establish the exact worst-case rate of convergence of this scheme, and show that this worst-case behavior is exhibited by a certain convex
A Numerical Approach to Optimal Coherent Quantum LQG Controller Design Using Gradient Descent
Sichani, Arash Kh.; Vladimirov, Igor G.; Petersen, Ian R.
2016-01-01
This paper is concerned with coherent quantum linear quadratic Gaussian (CQLQG) control. The problem is to find a stabilizing measurement-free quantum controller for a quantum plant so as to minimize a mean square cost for the fully quantum closed-loop system. The plant and controller are open quantum systems interconnected through bosonic quantum fields. In comparison with the observation-actuation structure of classical controllers, coherent quantum feedback is less invasive to the quantum ...
Coded aperture optimization in compressive X-ray tomography: a gradient descent approach.
Cuadros, Angela P; Arce, Gonzalo R
2017-10-02
Coded aperture X-ray computed tomography (CT) has the potential to revolutionize X-ray tomography systems in medical imaging and air and rail transit security - both areas of global importance. It allows either a reduced set of measurements in X-ray CT without degradation in image reconstruction, or measure multiplexed X-rays to simplify the sensing geometry. Measurement reduction is of particular interest in medical imaging to reduce radiation, and airport security often imposes practical constraints leading to limited angle geometries. Coded aperture compressive X-ray CT places a coded aperture pattern in front of the X-ray source in order to obtain patterned projections onto a detector. Compressive sensing (CS) reconstruction algorithms are then used to recover the image. To date, the coded illumination patterns used in conventional CT systems have been random. This paper addresses the code optimization problem for general tomography imaging based on the point spread function (PSF) of the system, which is used as a measure of the sensing matrix quality which connects to the restricted isometry property (RIP) and coherence of the sensing matrix. The methods presented are general, simple to use, and can be easily extended to other imaging systems. Simulations are presented where the peak signal to noise ratios (PSNR) of the reconstructed images using optimized coded apertures exhibit significant gain over those attained by random coded apertures. Additionally, results using real X-ray tomography projections are presented.
Kopasakis, George
1997-01-01
Performance Seeking Control (PSC) attempts to find and control the process at the operating condition that will generate maximum performance. In this paper a nonlinear multivariable PSC methodology will be developed, utilizing the Fuzzy Model Reference Learning Control (FMRLC) and the method of Steepest Descent or Gradient (SDG). This PSC control methodology employs the SDG method to find the operating condition that will generate maximum performance. This operating condition is in turn passed to the FMRLC controller as a set point for the control of the process. The conventional SDG algorithm is modified in this paper in order for convergence to occur monotonically. For the FMRLC control, the conventional fuzzy model reference learning control methodology is utilized, with guidelines generated here for effective tuning of the FMRLC controller.
Gender difference in metacarpal descent of fifth metacarpal
International Nuclear Information System (INIS)
Rafique, A.; Ali, H.; Ghani, S.
2006-01-01
To determine the difference in metacarpal descent of fifth metacarpal between men and women. Skyline of the 2nd and 3rd metacarpals were used as reference line, from which the descent of the 5th metacarpal head was measured. The position of 5th metacarpal head was documented as angle X. Metacarpal descent was defined as the difference between angle 'X' in relaxed and clenched fist position. The relaxed position was standardized by placing the forearm, wrist and palm on a shaped woodblock such that the wrist would be held in 25 - 30 degree in extension by a triangular spur, supported the 3rd metacarpal only. It was ensured that the movement of 4th and 5th metacarpals were not impaired. Analysis of variance was performed to compare the significance of means between genders at p < 0.05 level of significance. Metacarpal descent of the 5th metacarpal of both hands was significantly greater for women, with a mean of 7 degree as compared with a mean of 4 degree for the men. This decrease in angle 'X' was significant for the right 5th metacarpal relaxed and fist position and the fist position on the left. In contrast, women showed no significant differences between the various age groups for any of the variables tested.There was no relationship between metacarpal descent and hand dominance.Difference in metacarpal descent between men and women is significant and must be kept in mind when hand function is evaluated in both genders to assess the outcome of treatment and rehabilitation. (author)
Flight Data Entry, Descent, and Landing (EDL) Repository
Martinez, Elmain M.; Winterhalter, Daniel
2012-01-01
Dr. Daniel Winterhalter, NASA Engineering and Safety Center Chief Engineer at the Jet Propulsion Laboratory, requested the NASA Engineering and Safety Center sponsor a 3-year effort to collect entry, descent, and landing material and to establish a NASA-wide archive to serve the material. The principle focus of this task was to identify entry, descent, and landing repository material that was at risk of being permanently lost due to damage, decay, and undocumented storage. To provide NASA-wide access to this material, a web-based digital archive was created. This document contains the outcome of the effort.
Exploring Constrained Creative Communication
DEFF Research Database (Denmark)
Sørensen, Jannick Kirk
2017-01-01
Creative collaboration via online tools offers a less ‘media rich’ exchange of information between participants than face-to-face collaboration. The participants’ freedom to communicate is restricted in means of communication, and rectified in terms of possibilities offered in the interface. How do...... these constrains influence the creative process and the outcome? In order to isolate the communication problem from the interface- and technology problem, we examine via a design game the creative communication on an open-ended task in a highly constrained setting, a design game. Via an experiment the relation...... between communicative constrains and participants’ perception of dialogue and creativity is examined. Four batches of students preparing for forming semester project groups were conducted and documented. Students were asked to create an unspecified object without any exchange of communication except...
Hybrid Steepest Descent Viscosity Method for Triple Hierarchical Variational Inequalities
Directory of Open Access Journals (Sweden)
L.-C. Ceng
2012-01-01
Full Text Available We consider a triple hierarchical variational inequality problem (in short, THVIP. By combining hybrid steepest descent method, viscosity method, and projection method, we propose an approximation method to compute the approximate solution of THVIP. We also study the strong convergence of the sequences generated by the proposed method to a solution of THVIP.
Stress within a Bicultural Context for Adolescents of Mexican Descent.
Romero, Andrea J.; Roberts, Robert E.
2003-01-01
Folkman and Lazarus's theory of stress and coping was used to develop a measure assessing the perceived stress within a bicultural context. Middle school students of Mexican descent (N=881) reported their perceived stress from intergenerational acculturation gaps, within-group discrimination, out-group discrimination, and monolingual stress.…
Neuromuscular function during stair descent in meniscectomized patients and controls
DEFF Research Database (Denmark)
Thorlund, Jonas Bloch; Roos, Ewa M; Aagaard, Per
2011-01-01
The aim of this study was to identify differences in knee range of motion (ROM), movement speed, ground reaction forces (GRF) profile, neuromuscular activity, and muscle coactivation during the transition between stair descent and level walking in meniscectomized patients at high risk of knee...
Women of African Descent: Persistence in Completing Doctorates
Iddrisu, Vannetta Bailey
2010-01-01
This study examines the educational persistence of women of African descent (WOAD) in pursuit of a doctorate degree at universities in the southeastern United States. WOAD are women of African ancestry born outside the African continent. These women are heirs to an inner dogged determination and spirit to survive despite all odds (Pulliam, 2003,…
Screening for homozygosity by descent in families with autosomal
Indian Academy of Sciences (India)
Home; Journals; Journal of Genetics; Volume 81; Issue 2 ... Perspectives Volume 81 Issue 2 August 2002 pp 59-63 ... disease locus in families with the recessive form of the disease, we used the approach of screening for homozygosity by descent in offspring of consanguineous and nonconsanguineous families with RP.
Atkinson, David H.; Kazeminejad, Bobby; Lebreton*, Jean-Pierre
2015-04-01
Cassini/Huygens, a flagship mission to explore the rings, atmosphere, magnetic field, and moons that make up the Saturn system, is a joint endeavor of NASA, the European Space Agency, and Agenzia Spaziale Italiana. Comprising two spacecraft - a Saturn orbiter built by NASA and a Titan entry/descent probe built by the European Space Agency - Cassini/Huygens was launched in October 1997 and arrived at Saturn in 2004. The Huygens probe parachuted to the surface of Titan in January 2005. During the descent, six science instruments provided measurements of Titan's atmosphere, clouds, and winds, and photographed Titan's surface. It was recognized early in the Huygens program that to correctly interpret and correlate results from the probe science experiments and to provide a reference set of data for ground truth calibration of the Cassini orbiter remote sensing observations, an accurate reconstruction of the probe entry and descent trajectory and surface landing location would be necessary. The Huygens Descent Trajectory Working Group (DTWG) was chartered in 1996 as a subgroup of the Huygens Science Working Team. With membership comprising representatives from all the probe engineering and instrument teams as well as representatives of industry and the Cassini and Huygens Project Scientists, the DTWG presented an organizational framework within which instrument data was shared, the entry and descent trajectory reconstruction implemented, and the trajectory reconstruction efficiently disseminated. The primary goal of the Descent Trajectory Working Group was to develop retrieval methodologies for the probe descent trajectory reconstruction from the entry interface altitude of 1270 km to the surface using navigation data, and engineering and science data acquired by the instruments on the Huygens Probe, and to provide a reconstruction of the Huygens probe trajectory from entry to the surface of Titan that is maximally consistent with all available engineering and science
Minimal constrained supergravity
Directory of Open Access Journals (Sweden)
N. Cribiori
2017-01-01
Full Text Available We describe minimal supergravity models where supersymmetry is non-linearly realized via constrained superfields. We show that the resulting actions differ from the so called “de Sitter” supergravities because we consider constraints eliminating directly the auxiliary fields of the gravity multiplet.
Dalmau Codina, Ramon; Prats Menéndez, Xavier
2017-01-01
Continuous descent operations with controlled times of arrival at one or several metering fixes could enable environmentally friendly procedures without compromising terminal airspace capacity. This paper focuses on controlled time of arrival updates once the descent has been already initiated, assessing the feasible time window (and associated fuel consumption) of continuous descent operations requiring neither thrust nor speed-brake usage along the whole descent (i.e. only elevator control ...
De Candia, T.r.; Lee, S.H.; Yang, J.; Browning, B.L.; Gejman, P. V.; Levinson, D. F.; Mowry, B. J.; Hewitt, J.K.; Goddard, M.E.; O'Donovan, M.C.; Purcell, S.M.; Posthuma, D.; Visscher, P. M.; Wray, N.R.; Keller, M. C.
2013-01-01
To investigate the extent to which the proportion of schizophrenia's additive genetic variation tagged by SNPs is shared by populations of European and African descent, we analyzed the largest combined African descent (AD [n = 2,142]) and European descent (ED [n = 4,990]) schizophrenia case-control
A new conjugate gradient method and its global convergence under the exact line search
Omer, Osman; Rivaie, Mohd; Mamat, Mustafa; Abdalla, Awad
2014-12-01
The conjugate gradient methods are numerously used for solving nonlinear unconstrained optimization problems, especially of large scale. Their wide applications are due to their simplicity and low memory requirement. To analyze conjugate gradient methods, two types of line searches are used; exact and inexact. In this paper, we present a new method of nonlinear conjugate gradient methods under the exact line search. The theoretical analysis shows that the new method generates a descent direction in each iteration and globally convergent under the exact line search. Moreover, numerical experiments based on comparing the new method with other well known conjugate gradient methods show that the new is efficient for some unconstrained optimization problems.
ADAPTIVE SUBOPTIMAL CONTROL OF INPUT CONSTRAINED PLANTS
Directory of Open Access Journals (Sweden)
Valerii Azarskov
2011-03-01
Full Text Available Abstract. This paper deals with adaptive regulation of a discrete-time linear time-invariant plant witharbitrary bounded disturbances whose control input is constrained to lie within certain limits. The adaptivecontrol algorithm exploits the one-step-ahead control strategy and the gradient projection type estimationprocedure using the modified dead zone. The convergence property of the estimation algorithm is shown tobe ensured. The sufficient conditions guaranteeing the global asymptotical stability and simultaneously thesuboptimality of the closed-loop systems are derived. Numerical examples and simulations are presented tosupport the theoretical results.
Steepest-Ascent Constrained Simultaneous Perturbation for Multiobjective Optimization
DEFF Research Database (Denmark)
McClary, Dan; Syrotiuk, Violet; Kulahci, Murat
2011-01-01
that leverages information about the known gradient to constrain the perturbations used to approximate the others. We apply SP(SA)(2) to the cross-layer optimization of throughput, packet loss, and end-to-end delay in a mobile ad hoc network (MANET), a self-organizing wireless network. The results show that SP...
Van Hannen, E.J.; Van Agterveld, M.P.; Gons, H.J.; Laanbroek, H.J.
1998-01-01
A new Eucarya-specific 18S rDNA primer set was constructed and tested using denaturing gradient gel electrophoresis to analyze the genetic diversity of eukaryotic microorganisms in aquatic environments. All eukaryal lines of descent exhibited four or fewer nucleotide mismatches in the forward primer
A new convergent conjugate gradient method under the exact line search
Omer, Osman; Mamat, Mustafa; Rivaie, Mohd
2015-05-01
Conjugate gradient methods are widely used for unconstrained optimization problems, especially large scale problems. That is, for its simplicity, low memory requirement, and global convergence properties. In this paper, we study the global convergence properties of a new conjugate gradient method under the exact line search. Under some assumptions, the proofs of the sufficient descent property and the global convergence are given. The numerical results show that our new method is efficient for some unconstrained optimization problems.
Constrained Vapor Bubble Experiment
Gokhale, Shripad; Plawsky, Joel; Wayner, Peter C., Jr.; Zheng, Ling; Wang, Ying-Xi
2002-11-01
Microgravity experiments on the Constrained Vapor Bubble Heat Exchanger, CVB, are being developed for the International Space Station. In particular, we present results of a precursory experimental and theoretical study of the vertical Constrained Vapor Bubble in the Earth's environment. A novel non-isothermal experimental setup was designed and built to study the transport processes in an ethanol/quartz vertical CVB system. Temperature profiles were measured using an in situ PC (personal computer)-based LabView data acquisition system via thermocouples. Film thickness profiles were measured using interferometry. A theoretical model was developed to predict the curvature profile of the stable film in the evaporator. The concept of the total amount of evaporation, which can be obtained directly by integrating the experimental temperature profile, was introduced. Experimentally measured curvature profiles are in good agreement with modeling results. For microgravity conditions, an analytical expression, which reveals an inherent relation between temperature and curvature profiles, was derived.
Classification Constrained Dimensionality Reduction
Raich, Raviv; Costa, Jose A.; Damelin, Steven B.; Hero III, Alfred O.
2008-01-01
Dimensionality reduction is a topic of recent interest. In this paper, we present the classification constrained dimensionality reduction (CCDR) algorithm to account for label information. The algorithm can account for multiple classes as well as the semi-supervised setting. We present an out-of-sample expressions for both labeled and unlabeled data. For unlabeled data, we introduce a method of embedding a new point as preprocessing to a classifier. For labeled data, we introduce a method tha...
Environmental effects on hormonal regulation of testicular descent
DEFF Research Database (Denmark)
Toppari, J; Virtanen, H E; Skakkebaek, N E
2006-01-01
Regulation of testicular descent is hormonally regulated, but the reasons for maldescent remain unknown in most cases. The main regulatory hormones are Leydig cell-derived testosterone and insulin-like factor 3 (INSL3). Luteinizing hormone (LH) stimulates the secretion of these hormones, but the ...... hypothesize that an exposure to a mixture of chemicals with anti-androgenic or estrogenic properties (either their own activity or their effect on androgen-estrogen ratio) may be involved in cryptorchidism....... cause some cases of undescended testis. Similarly, androgen insensitivity or androgen deficiency can cause cryptorchidism. Estrogens have been shown to down regulate INSL3 and thereby cause maldescent. Thus, a reduced androgen-estrogen ratio may disturb testicular descent. Environmental effects changing...
Reversible cerebral vasoconstriction syndrome precipitated by airplane descent: Case report.
Hiraga, Akiyuki; Aotsuka, Yuya; Koide, Kyosuke; Kuwabara, Satoshi
2017-10-01
Background Reversible cerebral vasoconstriction syndrome (RCVS) is characterized by segmental vasospasm. Vasoactive agents and childbirth have been reported as precipitating factors for RCVS; however, RCVS induced by altitude change or air travel has rarely been reported. Case We present a case of a 74-year-old woman who presented with thunderclap headache during airplane descent. Magnetic resonance angiography demonstrated segmental vasoconstriction that improved 9 days after onset. Conclusion These findings indicate that airplane descent may be a trigger of RCVS. The time course of headache in the present case was similar to that of prolonged headache attributed to airplane travel, indicating that RCVS during air travel may have previously been overlooked and that some headache attributed to airplane travel cases may represent a milder form of RCVS.
RITD - Adapting Mars Entry, Descent and Landing System for Earth
Haukka, H.; Heilimo, J.; Harri, A.-M.; Aleksashkin, S.; Koryanov, V.; Arruego, I.; Schmidt, W.; Finchenko, V.; Martynov, M.; Ponomarenko, A.; Kazakovtsev, V.; Martin, S.
2015-10-01
We have developed an atmospheric re-entry and descent system concept based on inflatable hypersonic decelerator techniques that were originally developed for Mars. The ultimate goal of this EU-funded RITD-project (Re-entry: Inflatable Technology Development) was to assess the benefits of this technology when deploying small payloads from low Earth orbits to the surface of the Earth with modest costs. The principal goal was to assess and develop a preliminary EDLS design for the entire relevant range of aerodynamic regimes expected to be encountered in Earth's atmosphere during entry, descent and landing. Low Earth Orbit (LEO) and even Lunar applications envisaged include the use of the EDLS approach in returning payloads of 4-8 kg down to the surface.
Hyperrésolutions cubiques et descente cohomologique
Guillén, F; Pascual-Gainza, P; Puerta, F
1988-01-01
This monograph establishes a general context for the cohomological use of Hironaka's theorem on the resolution of singularities. It presents the theory of cubical hyperresolutions, and this yields the cohomological properties of general algebraic varieties, following Grothendieck's general ideas on descent as formulated by Deligne in his method for simplicial cohomological descent. These hyperrésolutions are applied in problems concerning possibly singular varieties: the monodromy of a holomorphic function defined on a complex analytic space, the De Rham cohmomology of varieties over a field of zero characteristic, Hodge-Deligne theory and the generalization of Kodaira-Akizuki-Nakano's vanishing theorem to singular algebraic varieties. As a variation of the same ideas, an application of cubical quasi-projective hyperresolutions to algebraic K-theory is given.
Additive preservers of the ascent, descent and related subsets
Czech Academy of Sciences Publication Activity Database
Mbekhta, M.; Müller, Vladimír; Oudghiri, M.
2014-01-01
Roč. 71, č. 1 (2014), s. 63-83 ISSN 0379-4024 R&D Projects: GA ČR GA201/09/0473; GA AV ČR IAA100190903 Institutional support: RVO:67985840 Keywords : additive preservers * ascent * descent Subject RIV: BA - General Mathematics Impact factor: 0.550, year: 2014 http://www.mathjournals.org/jot/2014-071-001/2014-071-001-004.html
Enumerating set partitions according to the number of descents of ...
Indian Academy of Sciences (India)
Abstract. Let P(n, k) denote the set of partitions of {1, 2,..., n} having exactly k blocks. In this paper, we find the generating function which counts the members of. P(n, k) according to the number of descents of size d or more, where d ≥ 1 is fixed. An explicit expression in terms of Stirling numbers of the second kind may be ...
Stair Descent in the Simple Hexapod ’RHex’
2003-01-01
robots that successfully do so. Notable exceptions are the Honda bipeds - P2, P3 and Asimo, and Raibert’s tethered biped , yet no specific publications...Stair Descent in the Simple Hexapod ‘RHex’ D. Campbell and M. Buehler dcampb@cim.mcgill.ca, buehler@cim.mcgill.ca, Ambulatory Robotics ...first controller that allows our small hexapod robot , RHex, to descend a wide variety of regular sized, “real-world” stairs. After selecting one of
Convergence results for a class of abstract continuous descent methods
Directory of Open Access Journals (Sweden)
Sergiu Aizicovici
2004-03-01
Full Text Available We study continuous descent methods for the minimization of Lipschitzian functions defined on a general Banach space. We establish convergence theorems for those methods which are generated by approximate solutions to evolution equations governed by regular vector fields. Since the complement of the set of regular vector fields is $sigma$-porous, we conclude that our results apply to most vector fields in the sense of Baire's categories.
Victimization and revictimization among women of Mexican descent.
Liendo, Nora Montalvo; Wardell, Diane W; Engebretson, Joan; Reininger, Belinda M
2011-01-01
To gain an understanding of the experiences of women of Mexican descent, born in Mexico or the United States who live with intimate partner abuse. The study was part of a larger study of the process of disclosure by women of Mexican descent who are subjected to intimate partner abuse. Descriptive qualitative approach. Two sites in a South Texas-Mexico border community: a woman's shelter and an outreach agency. Twenty-six women of Mexican descent were interviewed. A semistructured interview guide was used to elicit participants' views of their experiences with intimate partner abuse. These narratives illuminate how the process of victimization and revictimization creates an environment that blinds people to abuse, promotes denial of abuse, and leads women to remain in a harmful situation. Nurses and other health care and service providers working with women must take the initiative to assess for abuse; a few simple questions might change the woman's life and her children(s). © 2011 AWHONN, the Association of Women's Health, Obstetric and Neonatal Nurses.
Initial Descent of a Thermal and the Application to Downdraughts
Kruger, Emily; Burridge, Henry; Rooney, Gabriel; Linden, Paul
2017-11-01
Downward moving cold air within thunderstorms, known as downdraughts, can be used to determine the severity of a storm. Therefore an understanding of them is useful for weather forecasting. Typically in weather forecasting these downdrafts are modelled using the theory of a plume from from Morton, Taylor and Turner (1956), which inherently assumes that the plume is long and thin. Downdrafts are generally wider than they are high and hence deviate from the Morton, Taylor and Turner theory. We perform experiments using finite releases of dense fluid from a cylinder of varying lengths. By tracking the edges of the release we can find the velocity and radius of the descent and gravity current after impact. In doing so we find that the descent has two regimes, an initial phase and then a self similar thermal, and the axisymmetric gravity current varies depending on which regime the descent impacts the ground in. A theoretical model is proposed for this initial phase and compared to the experimental data. We hope that these results and future work will allow us to better inform forecasting of weather arising from such downdraughts.
Joint Chance-Constrained Dynamic Programming
Ono, Masahiro; Kuwata, Yoshiaki; Balaram, J. Bob
2012-01-01
This paper presents a novel dynamic programming algorithm with a joint chance constraint, which explicitly bounds the risk of failure in order to maintain the state within a specified feasible region. A joint chance constraint cannot be handled by existing constrained dynamic programming approaches since their application is limited to constraints in the same form as the cost function, that is, an expectation over a sum of one-stage costs. We overcome this challenge by reformulating the joint chance constraint into a constraint on an expectation over a sum of indicator functions, which can be incorporated into the cost function by dualizing the optimization problem. As a result, the primal variables can be optimized by a standard dynamic programming, while the dual variable is optimized by a root-finding algorithm that converges exponentially. Error bounds on the primal and dual objective values are rigorously derived. We demonstrate the algorithm on a path planning problem, as well as an optimal control problem for Mars entry, descent and landing. The simulations are conducted using a real terrain data of Mars, with four million discrete states at each time step.
Flight Management System Execution of Idle-Thrust Descents in Operations
Stell, Laurel L.
2011-01-01
To enable arriving aircraft to fly optimized descents computed by the flight management system (FMS) in congested airspace, ground automation must accurately predict descent trajectories. To support development of the trajectory predictor and its error models, commercial flights executed idle-thrust descents, and the recorded data includes the target speed profile and FMS intent trajectories. The FMS computes the intended descent path assuming idle thrust after top of descent (TOD), and any intervention by the controllers that alters the FMS execution of the descent is recorded so that such flights are discarded from the analysis. The horizontal flight path, cruise and meter fix altitudes, and actual TOD location are extracted from the radar data. Using more than 60 descents in Boeing 777 aircraft, the actual speeds are compared to the intended descent speed profile. In addition, three aspects of the accuracy of the FMS intent trajectory are analyzed: the meter fix crossing time, the TOD location, and the altitude at the meter fix. The actual TOD location is within 5 nmi of the intent location for over 95% of the descents. Roughly 90% of the time, the airspeed is within 0.01 of the target Mach number and within 10 KCAS of the target descent CAS, but the meter fix crossing time is only within 50 sec of the time computed by the FMS. Overall, the aircraft seem to be executing the descents as intended by the designers of the onboard automation.
Constraining entropic cosmology
Energy Technology Data Exchange (ETDEWEB)
Koivisto, Tomi S. [Institute for Theoretical Physics and the Spinoza Institute, Utrecht University, Leuvenlaan 4, Postbus 80.195, 3508 TD Utrecht (Netherlands); Mota, David F. [Institute of Theoretical Astrophysics, University of Oslo, 0315 Oslo (Norway); Zumalacárregui, Miguel, E-mail: t.s.koivisto@uu.nl, E-mail: d.f.mota@astro.uio.no, E-mail: miguelzuma@icc.ub.edu [Institute of Cosmos Sciences (ICC-IEEC), University of Barcelona, Marti i Franques 1, E-08028 Barcelona (Spain)
2011-02-01
It has been recently proposed that the interpretation of gravity as an emergent, entropic phenomenon might have nontrivial implications to cosmology. Here several such approaches are investigated and the underlying assumptions that must be made in order to constrain them by the BBN, SneIa, BAO and CMB data are clarified. Present models of inflation or dark energy are ruled out by the data. Constraints are derived on phenomenological parameterizations of modified Friedmann equations and some features of entropic scenarios regarding the growth of perturbations, the no-go theorem for entropic inflation and the possible violation of the Bekenstein bound for the entropy of the Universe are discussed and clarified.
Constrained blind deconvolution using Wirtinger flow methods
Walk, Philipp
2017-09-04
In this work we consider one-dimensional blind deconvolution with prior knowledge of signal autocorrelations in the classical framework of polynomial factorization. In particular this univariate case highly suffers from several non-trivial ambiguities and therefore blind deconvolution is known to be ill-posed in general. However, if additional autocorrelation information is available and the corresponding polynomials are co-prime, blind deconvolution is uniquely solvable up to global phase. Using lifting, the outer product of the unknown vectors is the solution to a (convex) semi-definite program (SDP) demonstrating that -theoretically- recovery is computationally tractable. However, for practical applications efficient algorithms are required which should operate in the original signal space. To this end we also discuss a gradient descent algorithm (Wirtinger flow) for the original non-convex problem. We demonstrate numerically that such an approach has performance comparable to the semidefinite program in the noisy case. Our work is motivated by applications in blind communication scenarios and we will discuss a specific signaling scheme where information is encoded into polynomial roots.
Modeling of magma descent and volcano deformation during a vulcanian eruption
Minowa, T.; Nishimura, T.
2013-12-01
Volcanic edifice generally deflates due to the discharge of magma in the conduit or reservoir when an eruption occurs. Contrary, recent geodetic observations for vulcanian eruptions of Showa crater at Sakurajima, Japan, show uplift toward the crater at the beginning of eruptions (Iguchi, 2013). In this study, we explain such apparently unexpected deformations by considering magma descent processes in a shallow conduit associated with vulcanian eruptions. A vulcanian eruption is simplified to be triggered by a removal of cap-rock that pressurizes magma in the conduit. Magma in the upper part of conduit is fragmented by large pressure differences built up in the conduit to rapidly effuse volcanic ash. The fragmentation surface propagates downward as volcanic ash ejects. Such magma descent during eruption is formulated by Koyaguchi and Mitani (2005). We propose a moving pressure source model for calculating volcano deformation, following their model. The normal stress acting on the conduit wall is reduced after the passage of the fragmentation surface, which acts as a deflation source. Upward drag force works on the conduit wall bellow the fragmentation surface where a high pressure gradient is formed in the magma. These processes are described by seven model parameters: conduit length L, conduit radius, initial overpressure at the top of the conduit, initial position of the magma head, magma porosity, magma viscosity and descent rate of the fragmentation surface, U. We calculate tilt and strain at the foot of volcano with a conical topography with a height of 1km and inclination angle of 11 degrees by using 3-D boundary element method. We assume appropriate parameters for vulcanian eruptions at andesitic volcanoes such as Sakurajima volcano, and set a cylindrical conduit at the summit. Numerical calculations of volcano deformations at 1-4 km distances from the conduit show following characteristics. Uplift toward the crater appears just after an eruption, because
The genetic basis of deafness in populations of African descent.
Rudman, Jason R; Kabahuma, Rosemary I; Bressler, Sara E; Feng, Yong; Blanton, Susan H; Yan, Denise; Liu, Xue-Zhong
2017-06-20
Hearing loss is the most common sensorineural disorder worldwide and is associated with more than 1000 mutations in more than 90 genes. While mutations in genes such as GJB2 (gap-junction protein β 2) and GJB6 (gap-junction protein β 6) are highly prevalent in Caucasian, Asian, and Middle Eastern populations, they are rare in both native African populations and those of African descent. The objective of this paper is to review the current knowledge regarding the epidemiology and genetics of hearing loss in African populations with a focus on native sub-Saharan African populations. Environmental etiologies related to poor access to healthcare and perinatal care account for the majority of cases. Syndromic etiologies including Waardenburg, Pendred and Usher syndromes are uncommon causes of hearing loss in these populations. Of the non-syndromic causes, common mutations in GJB2 and GJB6 are rarely implicated in populations of African descent. Recent use of next-generation sequencing (NGS) has identified several candidate deafness genes in African populations from Nigeria and South Africa that are unique when compared to common causative mutations worldwide. Researchers also recently described a dominant mutation in MYO3a in an African American family with non-syndromic hearing loss. The use of NGS and specialized panels will aid in identifying rare and novel mutations in a more cost- and time-effective manner. The identification of common hearing loss mutations in indigenous African populations will pave the way for translation into genetic deafness research in populations of African descent worldwide. Copyright © 2017 Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and Genetics Society of China. Published by Elsevier Ltd. All rights reserved.
A new method for forecasting the solar cycle descent time
Directory of Open Access Journals (Sweden)
Kakad Bharati
2015-01-01
Full Text Available The prediction of an extended solar minimum is extremely important because of the severity of its impact on the near-earth space. Here, we present a new method for predicting the descent time of the forthcoming solar cycle (SC; the method is based on the estimation of the Shannon entropy. We use the daily and monthly smoothed international sunspot number. For each nth SC, we compute the parameter [Tpre]n by using information on the descent and ascent times of the n − 3th and nth SCs, respectively. We find that [Tpre] of nth SC and entropy can be effectively used to predict the descent time of the n + 2th SC. The correlation coefficient between [Td]n+2 − [Tpre]n and [E]n is found to be 0.95. Using these parameters the prediction model is developed. Solar magnetic field and F10.7 flux data are available for SCs 21–22 and 19–23, respectively, and they are also utilized to get estimates of the Shannon entropy. It is found that the Shannon entropy, a measure of randomness inherent in the SC, is reflected well in the various proxies of the solar activity (viz sunspot, magnetic field, F10.7 flux. The applicability and accuracy of the prediction model equation is verified by way of association of least entropy values with the Dalton minimum. The prediction model equation also provides possible criteria for the occurrence of unusually longer solar minima.
The Descent Set and Connectivity Set of a Permutation
Stanley, Richard P.
2005-08-01
The descent set D(w) of a permutation w of 1,2,...,n is a standard and well-studied statistic. We introduce a new statistic, the connectivity set C(w), and show that it is a kind of dual object to D(w). The duality is stated in terms of the inverse of a matrix that records the joint distribution of D(w) and C(w). We also give a variation involving permutations of a multiset and a q-analogue that keeps track of the number of inversions of w.
Minimum descent time along a set of connected inclined planes
Mungan, Carl E.; Lipscombe, Trevor C.
2017-07-01
The time required for a particle to slide frictionlessly down a set of ramps connected end to end can be minimized numerically as a function of the coordinates of the connection points between ramps and compared to the exact cycloidal solution of the brachistochrone problem. It is found that a set of just three joined ramps over a large range of geometrical aspect ratios has a descent time within 5% of the optimal cycloid. The special case where the particle starts and ends at the same height has sufficient symmetry that it can be analyzed analytically using algebra alone. The level of analysis is appropriate to an undergraduate classical mechanics course.
Regularization Paths for Generalized Linear Models via Coordinate Descent
Directory of Open Access Journals (Sweden)
Jerome Friedman
2010-02-01
Full Text Available We develop fast algorithms for estimation of generalized linear models with convex penalties. The models include linear regression, two-class logistic regression, and multi- nomial regression problems while the penalties include ℓ1 (the lasso, ℓ2 (ridge regression and mixtures of the two (the elastic net. The algorithms use cyclical coordinate descent, computed along a regularization path. The methods can handle large problems and can also deal efficiently with sparse features. In comparative timings we find that the new algorithms are considerably faster than competing methods.
DEFF Research Database (Denmark)
Yiu, Man Lung; Karras, Panagiotis; Mamoulis, Nikos
2008-01-01
We introduce a novel spatial join operator, the ring-constrained join (RCJ). Given two sets P and Q of spatial points, the result of RCJ consists of pairs (p, q) (where p ε P, q ε Q) satisfying an intuitive geometric constraint: the smallest circle enclosing p and q contains no other points in P, Q....... This new operation has important applications in decision support, e.g., placing recycling stations at fair locations between restaurants and residential complexes. Clearly, RCJ is defined based on a geometric constraint but not on distances between points. Thus, our operation is fundamentally different...... from the conventional distance joins and closest pairs problems. We are not aware of efficient processing algorithms for RCJ in the literature. A brute-force solution requires computational cost quadratic to input size and it does not scale well for large datasets. In view of this, we develop efficient...
An improved partial bundle method for linearly constrained minimax problems
Directory of Open Access Journals (Sweden)
Chunming Tang
2016-02-01
Full Text Available In this paper, we propose an improved partial bundle method for solving linearly constrained minimax problems. In order to reduce the number of component function evaluations, we utilize a partial cutting-planes model to substitute for the traditional one. At each iteration, only one quadratic programming subproblem needs to be solved to obtain a new trial point. An improved descent test criterion is introduced to simplify the algorithm. The method produces a sequence of feasible trial points, and ensures that the objective function is monotonically decreasing on the sequence of stability centers. Global convergence of the algorithm is established. Moreover, we utilize the subgradient aggregation strategy to control the size of the bundle and therefore overcome the difficulty of computation and storage. Finally, some preliminary numerical results show that the proposed method is effective.
A Sequential Quadratically Constrained Quadratic Programming Method of Feasible Directions
International Nuclear Information System (INIS)
Jian Jinbao; Hu Qingjie; Tang Chunming; Zheng Haiyan
2007-01-01
In this paper, a sequential quadratically constrained quadratic programming method of feasible directions is proposed for the optimization problems with nonlinear inequality constraints. At each iteration of the proposed algorithm, a feasible direction of descent is obtained by solving only one subproblem which consist of a convex quadratic objective function and simple quadratic inequality constraints without the second derivatives of the functions of the discussed problems, and such a subproblem can be formulated as a second-order cone programming which can be solved by interior point methods. To overcome the Maratos effect, an efficient higher-order correction direction is obtained by only one explicit computation formula. The algorithm is proved to be globally convergent and superlinearly convergent under some mild conditions without the strict complementarity. Finally, some preliminary numerical results are reported
Shape tracking with occlusions via coarse-to-fine region-based sobolev descent
Yang, Yanchao
2015-05-01
We present a method to track the shape of an object from video. The method uses a joint shape and appearance model of the object, which is propagated to match shape and radiance in subsequent frames, determining object shape. Self-occlusions and dis-occlusions of the object from camera and object motion pose difficulties to joint shape and appearance models in tracking. They are unable to adapt to new shape and appearance information, leading to inaccurate shape detection. In this work, we model self-occlusions and dis-occlusions in a joint shape and appearance tracking framework. Self-occlusions and the warp to propagate the model are coupled, thus we formulate a joint optimization problem. We derive a coarse-to-fine optimization method, advantageous in tracking, that initially perturbs the model by coarse perturbations before transitioning to finer-scale perturbations seamlessly. This coarse-to-fine behavior is automatically induced by gradient descent on a novel infinite-dimensional Riemannian manifold that we introduce. The manifold consists of planar parameterized regions, and the metric that we introduce is a novel Sobolev metric. Experiments on video exhibiting occlusions/dis-occlusions, complex radiance and background show that occlusion/dis-occlusion modeling leads to superior shape accuracy. © 2014 IEEE.
Linearly constrained minimax optimization
DEFF Research Database (Denmark)
Madsen, Kaj; Schjær-Jacobsen, Hans
1978-01-01
We present an algorithm for nonlinear minimax optimization subject to linear equality and inequality constraints which requires first order partial derivatives. The algorithm is based on successive linear approximations to the functions defining the problem. The resulting linear subproblems...... are solved in the minimax sense subject to the linear constraints. This ensures a feasible-point algorithm. Further, we introduce local bounds on the solutions of the linear subproblems, the bounds being adjusted automatically, depending on the quality of the linear approximations. It is proved...... that the algorithm will always converge to the set of stationary points of the problem, a stationary point being defined in terms of the generalized gradients of the minimax objective function. It is further proved that, under mild regularity conditions, the algorithm is identical to a quadratically convergent...
Energy Technology Data Exchange (ETDEWEB)
Verde, Licia; Jimenez, Raul [Institute of Cosmos Sciences, University of Barcelona, IEEC-UB, Martí Franquès, 1, E08028 Barcelona (Spain); Bellini, Emilio [University of Oxford, Denys Wilkinson Building, Keble Road, Oxford, OX1 3RH (United Kingdom); Pigozzo, Cassio [Instituto de Física, Universidade Federal da Bahia, Salvador, BA (Brazil); Heavens, Alan F., E-mail: liciaverde@icc.ub.edu, E-mail: emilio.bellini@physics.ox.ac.uk, E-mail: cpigozzo@ufba.br, E-mail: a.heavens@imperial.ac.uk, E-mail: raul.jimenez@icc.ub.edu [Imperial Centre for Inference and Cosmology (ICIC), Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)
2017-04-01
We investigate our knowledge of early universe cosmology by exploring how much additional energy density can be placed in different components beyond those in the ΛCDM model. To do this we use a method to separate early- and late-universe information enclosed in observational data, thus markedly reducing the model-dependency of the conclusions. We find that the 95% credibility regions for extra energy components of the early universe at recombination are: non-accelerating additional fluid density parameter Ω{sub MR} < 0.006 and extra radiation parameterised as extra effective neutrino species 2.3 < N {sub eff} < 3.2 when imposing flatness. Our constraints thus show that even when analyzing the data in this largely model-independent way, the possibility of hiding extra energy components beyond ΛCDM in the early universe is seriously constrained by current observations. We also find that the standard ruler, the sound horizon at radiation drag, can be well determined in a way that does not depend on late-time Universe assumptions, but depends strongly on early-time physics and in particular on additional components that behave like radiation. We find that the standard ruler length determined in this way is r {sub s} = 147.4 ± 0.7 Mpc if the radiation and neutrino components are standard, but the uncertainty increases by an order of magnitude when non-standard dark radiation components are allowed, to r {sub s} = 150 ± 5 Mpc.
Constraining neutrinoless double beta decay
International Nuclear Information System (INIS)
Dorame, L.; Meloni, D.; Morisi, S.; Peinado, E.; Valle, J.W.F.
2012-01-01
A class of discrete flavor-symmetry-based models predicts constrained neutrino mass matrix schemes that lead to specific neutrino mass sum-rules (MSR). We show how these theories may constrain the absolute scale of neutrino mass, leading in most of the cases to a lower bound on the neutrinoless double beta decay effective amplitude.
Frequency-domain full-waveform inversion with non-linear descent directions
Geng, Yu; Pan, Wenyong; Innanen, Kristopher A.
2018-05-01
Full-waveform inversion (FWI) is a highly non-linear inverse problem, normally solved iteratively, with each iteration involving an update constructed through linear operations on the residuals. Incorporating a flexible degree of non-linearity within each update may have important consequences for convergence rates, determination of low model wavenumbers and discrimination of parameters. We examine one approach for doing so, wherein higher order scattering terms are included within the sensitivity kernel during the construction of the descent direction, adjusting it away from that of the standard Gauss-Newton approach. These scattering terms are naturally admitted when we construct the sensitivity kernel by varying not the current but the to-be-updated model at each iteration. Linear and/or non-linear inverse scattering methodologies allow these additional sensitivity contributions to be computed from the current data residuals within any given update. We show that in the presence of pre-critical reflection data, the error in a second-order non-linear update to a background of s0 is, in our scheme, proportional to at most (Δs/s0)3 in the actual parameter jump Δs causing the reflection. In contrast, the error in a standard Gauss-Newton FWI update is proportional to (Δs/s0)2. For numerical implementation of more complex cases, we introduce a non-linear frequency-domain scheme, with an inner and an outer loop. A perturbation is determined from the data residuals within the inner loop, and a descent direction based on the resulting non-linear sensitivity kernel is computed in the outer loop. We examine the response of this non-linear FWI using acoustic single-parameter synthetics derived from the Marmousi model. The inverted results vary depending on data frequency ranges and initial models, but we conclude that the non-linear FWI has the capability to generate high-resolution model estimates in both shallow and deep regions, and to converge rapidly, relative to a
Power-constrained supercomputing
Bailey, Peter E.
As we approach exascale systems, power is turning from an optimization goal to a critical operating constraint. With power bounds imposed by both stakeholders and the limitations of existing infrastructure, achieving practical exascale computing will therefore rely on optimizing performance subject to a power constraint. However, this requirement should not add to the burden of application developers; optimizing the runtime environment given restricted power will primarily be the job of high-performance system software. In this dissertation, we explore this area and develop new techniques that extract maximum performance subject to a particular power constraint. These techniques include a method to find theoretical optimal performance, a runtime system that shifts power in real time to improve performance, and a node-level prediction model for selecting power-efficient operating points. We use a linear programming (LP) formulation to optimize application schedules under various power constraints, where a schedule consists of a DVFS state and number of OpenMP threads for each section of computation between consecutive message passing events. We also provide a more flexible mixed integer-linear (ILP) formulation and show that the resulting schedules closely match schedules from the LP formulation. Across four applications, we use our LP-derived upper bounds to show that current approaches trail optimal, power-constrained performance by up to 41%. This demonstrates limitations of current systems, and our LP formulation provides future optimization approaches with a quantitative optimization target. We also introduce Conductor, a run-time system that intelligently distributes available power to nodes and cores to improve performance. The key techniques used are configuration space exploration and adaptive power balancing. Configuration exploration dynamically selects the optimal thread concurrency level and DVFS state subject to a hardware-enforced power bound
Constrained Minimization Algorithms
Lantéri, H.; Theys, C.; Richard, C.
2013-03-01
In this paper, we consider the inverse problem of restoring an unknown signal or image, knowing the transformation suffered by the unknowns. More specifically we deal with transformations described by a linear model linking the unknown signal to an unnoisy version of the data. The measured data are generally corrupted by noise. This aspect of the problem is presented in the introduction for general models. In Section 2, we introduce the linear models, and some examples of linear inverse problems are presented. The specificities of the inverse problems are briefly mentionned and shown on a simple example. In Section 3, we give some information on classical distances or divergences. Indeed, an inverse problem is generally solved by minimizing a discrepancy function (divergence or distance) between the measured data and the model (here linear) of such data. Section 4 deals with the likelihood maximization and with their links with divergences minimization. The physical constraints on the solution are indicated and the Split Gradient Method (SGM) is detailed in Section 5. A constraint on the inferior bound of the solution is introduced at first; the positivity constraint is a particular case of such a constraint. We show how to obtain strictly, the multiplicative form of the algorithms. In a second step, the so-called flux constraint is introduced, and a complete algorithmic form is given. In Section 6 we give some brief information on acceleration method of such algorithms. A conclusion is given in Section 7.
Nonmonotone Adaptive Barzilai-Borwein Gradient Algorithm for Compressed Sensing
Directory of Open Access Journals (Sweden)
Yuanying Qiu
2014-01-01
Full Text Available We study a nonmonotone adaptive Barzilai-Borwein gradient algorithm for l1-norm minimization problems arising from compressed sensing. At each iteration, the generated search direction enjoys descent property and can be easily derived by minimizing a local approximal quadratic model and simultaneously taking the favorable structure of the l1-norm. Under some suitable conditions, its global convergence result could be established. Numerical results illustrate that the proposed method is promising and competitive with the existing algorithms NBBL1 and TwIST.
On Belonging: The American Adolescent of Arab Descent.
Khouri, Lama Z
2016-08-01
Although American families of Arab origin come from 22 countries and from varied backgrounds and cultures, reports suggest that they suffer equally from acculturation stress, stereotyping, discrimination, and the reverberations of the aftermath of September 11 as well as global affairs. However, because children and adolescents from these families, particularly those who are newly arrived immigrants, tend to do well in school, they are rarely targeted by research or policy. This article uses the narratives of 5 middle school age male students from Arab descent who were in a support group that met for 3 years (2004-2007), beginning shortly after President George W. Bush's declaration of the war on the "axis of evil." I used vignettes from this group to illustrate the stressors this population faces. The final section suggests an option for supporting this population. © 2016 Wiley Periodicals, Inc.
Adapting Mars Entry, Descent and Landing System for Earth
Heilimo, J.; Harri, A.-M.; Aleksashkin, S.; Koryanov, V.; Guerrero, H.; Schmidt, W.; Haukka, H.; Finchenko, V.; Martynov, M.; Ostresko, B.; Ponomarenko, A.; Kazakovtsev, V.; Arruego, I.; Martin, S.; Siili, T.
2013-09-01
In 2001 - 2011 an inflatable Entry, Descent and Landing System (EDLS) for Martian atmosphere was developed by FMI and the MetNet team. This MetNet Mars Lander EDLS is used in both the initial deceleration during atmospheric entry and in the final deceleration before the semi-hard impact of the penetrator to Martian surface. The EDLS design is ingenious and its applicability to Earth's atmosphere is studied in the on-going project. In particular, the behavior of the system in the critical transonic aerodynamic (from hypersonic to subsonic) regime will be investigated. This project targets to analyze and test the transonic behavior of this compact and light weight payload entry system to Earth's atmosphere [1]. Scaling and adaptation for terrestrial atmospheric conditions, instead of a completely new design, is a favorable approach for providing a new re-entry vehicle for terrestrial space applications.
Analysis of Atmospheric Mesoscale Models for Entry, Descent and Landing
Kass, D. M.; Schofield, J. T.; Michaels, T. I.; Rafkin, S. C. R.; Richardson, M. I.; Toigo, A. D.
2003-01-01
Each Mars Exploration Rover (MER) is sensitive to the martian winds encountered near the surface during the Entry, Descent and Landing (EDL) process. These winds are strongly influenced by local (mesoscale) conditions. In the absence of suitable wind observations, wind fields predicted by martian mesoscale atmospheric models have been analyzed to guide landing site selection. Two different models were used, the MRAMS model and the Mars MM5 model. In order to encompass both models and render their results useful to the EDL engineering team, a series of statistical techniques were applied to the model results. These analyses cover the high priority landing sites during the expected landing times (1200 to 1500 local time). The number of sites studied is limited by the computational and analysis cost of the mesoscale models.
Human Mars Entry, Descent, and Landing Architecture Study Overview
Cianciolo, Alicia D.; Polsgrove, Tara T.
2016-01-01
The Entry, Descent, and Landing (EDL) Architecture Study is a multi-NASA center activity to analyze candidate EDL systems as they apply to human Mars landing in the context of the Evolvable Mars Campaign. The study, led by the Space Technology Mission Directorate (STMD), is performed in conjunction with the NASA's Science Mission Directorate and the Human Architecture Team, sponsored by NASA's Human Exploration and Operations Mission Directorate. The primary objective is to prioritize future STMD EDL technology investments by (1) generating Phase A-level designs for selected concepts to deliver 20 t human class payloads, (2) developing a parameterized mass model for each concept capable of examining payloads between 5 and 40 t, and (3) evaluating integrated system performance using trajectory simulations. This paper summarizes the initial study results.
Dynamic MR colpocystorectography assessing pelvic-floor descent
Energy Technology Data Exchange (ETDEWEB)
Lienemann, A.; Kohz, P.; Reiser, M. [Department of Radiology, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistrasse 15, D-81 377 Munich (Germany); Anthuber, C.; Baron, A. [Department of Obstetrics and Gynecology, Klinikum Grosshadern, Ludwig-Maximilians-University, Marchioninistrasse 15, D-81 377 Munich (Germany)
1997-10-01
Magnetic resonance colpocystorectography (MR-CCRG) is presented in the evaluation of patients with pelvic-floor disorders. Five healthy volunteers and 44 female patients with isolated or combined visceral descent underwent dynamic MRI and dynamic fluoroscopy (DF). MR-CCRG was performed with the patient in a supine position using a True FISP sequence (1 image/1.2 s; in-plane resolution 1.02 mm) during pelvic floor contraction, relaxation, and straining maneuvers. Relevant organs, such as urethra, bladder, vagina, and rectum, were opacified by using a saline solution, Magnevist (Schering AG, Berlin, Germany), and sonography gel, respectively. The clinical evaluation and the intraoperative results (30 cases) were used as reference. MR-CCRG and DF were non-diagnostic in 3 cases each. Most patients had a combined type of visceral prolapse, the most frequent combination being a vaginal vault prolapse and a cystocele. The points of reference were sufficiently outlined by DF and MR-CCRG. In comparison with the clinical and intraoperative results, MR-CCRG proved to be especially beneficial in the diagnosis of different types of enteroceles including a uterovaginal prolapse. MR-CCRG showed an equal or higher sensitivity and specificity for all individual sites when compared with DF. Also, predominant herniation obscuring other concomitant prolapse could be verified in 8 cases. MR-CCRG is superior to DF and accurately depicts pelvic-floor descent and prolapse in women. The possibility of dynamic presentation (see enclosed CD-ROM) allows for a better understanding of the organ movements within a given topographic reference setting. (orig.). With 5 figs., 3 tabs.
Ethnic Identity and Acculturative Stress as Mediators of Depression in Students of Asian Descent
Lantrip, Crystal; Mazzetti, Francesco; Grasso, Joseph; Gill, Sara; Miller, Janna; Haner, Morgynn; Rude, Stephanie; Awad, Germine
2015-01-01
This study underscored the importance of addressing the well-being of college students of Asian descent, because these students had higher rates of depression and lower positive feelings about their ethnic group compared with students of European descent, as measured by the Affirmation subscale of the Ethnic Identity Scale. Affirmation mediated…
The Role of la Familia for Women of Mexican Descent Who Are Leaders in Higher Education
Elizondo, Sandra Gray
2012-01-01
The purpose of this qualitative case study was to describe the role of "la familia" for women of Mexican descent as it relates to their development as leaders and their leadership in academia. Purposeful sampling was utilized to reach the goal of 18 participants who were female academic leaders of Mexican descent teaching full time in…
Verhoeven, Ronald; Dalmau Codina, Ramon; Prats Menéndez, Xavier; de Gelder, Nico
2014-01-01
1 Abstract In this paper an initial implementation of a real - time aircraft trajectory optimization algorithm is presented . The aircraft trajectory for descent and approach is computed for minimum use of thrust and speed brake in support of a “green” continuous descent and approach flight operation, while complying with ATC time constraints for maintaining runway throughput and co...
Ascent, descent, nullity, defect, and related notions for linear relations in linear spaces
Sandovici, Adrian; de Snoo, Henk; Winkler, Henrik
2007-01-01
For a linear relation in a linear space the concepts of ascent, descent, nullity, and defect are introduced and studied. It is shown that the results of A.E. Taylor and M.A. Kaashoek concerning the relationship between ascent, descent, nullity, and defect for the case of linear operators remain
Ground reaction forces and frictional demands during stair descent: effects of age and illumination.
Christina, Kathryn A; Cavanagh, Peter R
2002-04-01
Stair descent is an inherently risky and demanding task that older adults often encounter in everyday life. It is believed that slip between the foot or shoe sole and the stair surface may play a role in stair related falls, however, there are no reports on slip resistance requirements for stair descent. The aim of this study was to determine the required coefficient of friction (RCOF) necessary for safe stair descent in 12 young and 12 older adults, under varied illuminance conditions. The RCOF during stair descent was found to be comparable in magnitude and time to that for overground walking, and thus, with adequate footwear and dry stair surfaces, friction does not appear to be a major determinant of stair safety. Illuminance level had little effect on the dependent variables quantified in this study. However, the older participants demonstrated safer strategies than the young during stair descent, as reflected by differences in the ground reaction forces and lower RCOF.
National Aeronautics and Space Administration — High-mass planetary surface access is one of NASA’s Grand Challenges involving entry, descent and landing (EDL). During the entry and descent phase,...
Lightweight cryptography for constrained devices
DEFF Research Database (Denmark)
Alippi, Cesare; Bogdanov, Andrey; Regazzoni, Francesco
2014-01-01
Lightweight cryptography is a rapidly evolving research field that responds to the request for security in resource constrained devices. This need arises from crucial pervasive IT applications, such as those based on RFID tags where cost and energy constraints drastically limit the solution...... complexity, with the consequence that traditional cryptography solutions become too costly to be implemented. In this paper, we survey design strategies and techniques suitable for implementing security primitives in constrained devices....
Two New PRP Conjugate Gradient Algorithms for Minimization Optimization Models.
Directory of Open Access Journals (Sweden)
Gonglin Yuan
Full Text Available Two new PRP conjugate Algorithms are proposed in this paper based on two modified PRP conjugate gradient methods: the first algorithm is proposed for solving unconstrained optimization problems, and the second algorithm is proposed for solving nonlinear equations. The first method contains two aspects of information: function value and gradient value. The two methods both possess some good properties, as follows: 1 βk ≥ 0 2 the search direction has the trust region property without the use of any line search method 3 the search direction has sufficient descent property without the use of any line search method. Under some suitable conditions, we establish the global convergence of the two algorithms. We conduct numerical experiments to evaluate our algorithms. The numerical results indicate that the first algorithm is effective and competitive for solving unconstrained optimization problems and that the second algorithm is effective for solving large-scale nonlinear equations.
Physics-based Entry, Descent and Landing Risk Model
Gee, Ken; Huynh, Loc C.; Manning, Ted
2014-01-01
A physics-based risk model was developed to assess the risk associated with thermal protection system failures during the entry, descent and landing phase of a manned spacecraft mission. In the model, entry trajectories were computed using a three-degree-of-freedom trajectory tool, the aerothermodynamic heating environment was computed using an engineering-level computational tool and the thermal response of the TPS material was modeled using a one-dimensional thermal response tool. The model was capable of modeling the effect of micrometeoroid and orbital debris impact damage on the TPS thermal response. A Monte Carlo analysis was used to determine the effects of uncertainties in the vehicle state at Entry Interface, aerothermodynamic heating and material properties on the performance of the TPS design. The failure criterion was set as a temperature limit at the bondline between the TPS and the underlying structure. Both direct computation and response surface approaches were used to compute the risk. The model was applied to a generic manned space capsule design. The effect of material property uncertainty and MMOD damage on risk of failure were analyzed. A comparison of the direct computation and response surface approach was undertaken.
Estimating Controller Intervention Probabilities for Optimized Profile Descent Arrivals
Meyn, Larry A.; Erzberger, Heinz; Huynh, Phu V.
2011-01-01
Simulations of arrival traffic at Dallas/Fort-Worth and Denver airports were conducted to evaluate incorporating scheduling and separation constraints into advisories that define continuous descent approaches. The goal was to reduce the number of controller interventions required to ensure flights maintain minimum separation distances of 5 nmi horizontally and 1000 ft vertically. It was shown that simply incorporating arrival meter fix crossing-time constraints into the advisory generation could eliminate over half of the all predicted separation violations and more than 80% of the predicted violations between two arrival flights. Predicted separation violations between arrivals and non-arrivals were 32% of all predicted separation violations at Denver and 41% at Dallas/Fort-Worth. A probabilistic analysis of meter fix crossing-time errors is included which shows that some controller interventions will still be required even when the predicted crossing-times of the advisories are set to add a 1 or 2 nmi buffer above the minimum in-trail separation of 5 nmi. The 2 nmi buffer was shown to increase average flight delays by up to 30 sec when compared to the 1 nmi buffer, but it only resulted in a maximum decrease in average arrival throughput of one flight per hour.
Evolution and ecology of directed aerial descent in arboreal ants.
Yanoviak, Stephen P; Munk, Yonatan; Dudley, Robert
2011-12-01
Directed aerial descent (DAD) is used by a variety of arboreal animals to escape predators, to remain in the canopy, and to access resources. Here, we build upon the discovery of DAD in ants of tropical canopies by summarizing its known phylogenetic distribution among ant genera, and within both the subfamily Pseudomyrmecinae and the genus Cephalotes. DAD has multiple evolutionary origins in ants, occurring independently in numerous genera in the subfamilies Myrmicinae, Formicinae, and Pseudomyrmecinae. Ablation experiments and video recordings of ants in a vertical wind tunnel showed that DAD in Cephalotes atratus is achieved via postural changes, specifically orientation of the legs and gaster. The occurrence of DAD in Formicinae indicates that the presence of a postpetiole is not essential for the behavior. Evidence to date indicates that gliding behavior is accomplished by visual targeting mediated by the compound eyes, and is restricted to diurnally active ants that nest in trees. Occlusion of ocelli in Pseudomyrmex gracilis workers had no effect on their success or performance in gliding. Experimental assessment of the fate of ants that fall to the understory showed that ants landing in water are 15 times more likely to suffer lethal attacks than are ants landing in leaf litter. Variation in both the aerodynamic mechanisms and selective advantages of DAD merits further study given the broad taxonomic diversity of arboreal ants that engage in this intriguing form of flight.
Race, language, and mental evolution in Darwin's descent of man.
Alter, Stephen G
2007-01-01
Charles Darwin was notoriously ambiguous in his remarks about the relationship between human evolution and biological race. He stressed the original unity of the races, yet he also helped to popularize the notion of a racial hierarchy filling the gaps between the highest anthropoids and civilized Europeans. A focus on Darwin's explanation of how humans initially evolved, however, shows that he mainly stressed not hierarchy but a version of humanity's original mental unity. In his book The Descent of Man, Darwin emphasized a substantial degree of mental development (including the incipient use of language) in the early, monogenetic phase of human evolution. This development, he argued, necessarily came before primeval man's numerical increase, geographic dispersion, and racial diversification, because only thus could one explain how that group was able to spread at the expense of rival ape-like populations. This scenario stood opposed to a new evolutionary polygenism formulated in the wake of Darwin's Origin of Species by his ostensible supporters Alfred Russel Wallace and Ernst Haeckel. Darwin judged this outlook inadequate to the task of explaining humanity's emergence. (c) 2007 Wiley Periodicals, Inc.
HLA Type Inference via Haplotypes Identical by Descent
Setty, Manu N.; Gusev, Alexander; Pe'Er, Itsik
The Human Leukocyte Antigen (HLA) genes play a major role in adaptive immune response and are used to differentiate self antigens from non self ones. HLA genes are hyper variable with nearly every locus harboring over a dozen alleles. This variation plays an important role in susceptibility to multiple autoimmune diseases and needs to be matched on for organ transplantation. Unfortunately, HLA typing by serological methods is time consuming and expensive compared to high throughput Single Nucleotide Polymorphism (SNP) data. We present a new computational method to infer per-locus HLA types using shared segments Identical By Descent (IBD), inferred from SNP genotype data. IBD information is modeled as graph where shared haplotypes are explored among clusters of individuals with known and unknown HLA types to identify the latter. We analyze performance of the method in a previously typed subset of the HapMap population, achieving accuracy of 96% in HLA-A, 94% in HLA-B, 95% in HLA-C, 77% in HLA-DR1, 93% in HLA-DQA1 and 90% in HLA-DQB1 genes. We compare our method to a tag SNP based approach and demonstrate higher sensitivity and specificity. Our method demonstrates the power of using shared haplotype segments for large-scale imputation at the HLA locus.
Human Mars Entry, Descent and Landing Architectures Study Overview
Polsgrove, Tara T.; Dwyer Cianciolo, Alicia
2016-01-01
Landing humans on Mars will require entry, descent and landing (EDL) capability beyond the current state of the art. Nearly twenty times more delivered payload and an order of magnitude improvement in precision landing capability will be necessary. Several EDL technologies capable of meeting the human class payload delivery requirements are being considered. The EDL technologies considered include low lift-to-drag vehicles like Hypersonic Inflatable Aerodynamic Decelerators (HIAD), Adaptable Deployable Entry and Placement Technology (ADEPT), and mid range lift-to-drag vehicles like rigid aeroshell configurations. To better assess EDL technology options and sensitivities to future human mission design variations, a series of design studies has been conducted. The design studies incorporate EDL technologies with conceptual payload arrangements defined by the Evolvable Mars Campaign to evaluate the integrated system with higher fidelity than have been performed to date. This paper describes the results of the design studies for a lander design using the HIAD, ADEPT and rigid shell entry technologies and includes system and subsystem design details including mass and power estimates. This paper will review the point design for three entry configurations capable of delivering a 20 t human class payload to the surface of Mars.
Directory of Open Access Journals (Sweden)
Zhifeng Dai
2014-01-01
Full Text Available Combining the Rosen gradient projection method with the two-term Polak-Ribière-Polyak (PRP conjugate gradient method, we propose a two-term Polak-Ribière-Polyak (PRP conjugate gradient projection method for solving linear equality constraints optimization problems. The proposed method possesses some attractive properties: (1 search direction generated by the proposed method is a feasible descent direction; consequently the generated iterates are feasible points; (2 the sequences of function are decreasing. Under some mild conditions, we show that it is globally convergent with Armijio-type line search. Preliminary numerical results show that the proposed method is promising.
Robust non-gradient C subroutines for non-linear optimization
DEFF Research Database (Denmark)
Brock, Pernille; Madsen, Kaj; Nielsen, Hans Bruun
2004-01-01
This report presents a package of robust and easy-to-use C subroutines for solving unconstrained and constrained non-linear optimization problems, where gradient information is not required. The intention is that the routines should use the currently best algorithms available. All routines have...... and constrained optimization but requiring gradient information. The parameter lists for the subroutines in both collections are similar so it is easy to switch between the non- gradient and the gradient methods. All of the subroutine names in this report start with MI0. The corresponding names of the gradient...... subroutines are obtained by changing 0 to 1. The present report is a new and updated version of a previous report NI-91-04 with the title Non-gradient c Subroutines for Non- Linear Optimization, [16]. Both the previous and the present report describe a collection of subroutines, which have been translated...
A modified form of conjugate gradient method for unconstrained optimization problems
Ghani, Nur Hamizah Abdul; Rivaie, Mohd.; Mamat, Mustafa
2016-06-01
Conjugate gradient (CG) methods have been recognized as an interesting technique to solve optimization problems, due to the numerical efficiency, simplicity and low memory requirements. In this paper, we propose a new CG method based on the study of Rivaie et al. [7] (Comparative study of conjugate gradient coefficient for unconstrained Optimization, Aus. J. Bas. Appl. Sci. 5(2011) 947-951). Then, we show that our method satisfies sufficient descent condition and converges globally with exact line search. Numerical results show that our proposed method is efficient for given standard test problems, compare to other existing CG methods.
Ghani, N. H. A.; Mohamed, N. S.; Zull, N.; Shoid, S.; Rivaie, M.; Mamat, M.
2017-09-01
Conjugate gradient (CG) method is one of iterative techniques prominently used in solving unconstrained optimization problems due to its simplicity, low memory storage, and good convergence analysis. This paper presents a new hybrid conjugate gradient method, named NRM1 method. The method is analyzed under the exact and inexact line searches in given conditions. Theoretically, proofs show that the NRM1 method satisfies the sufficient descent condition with both line searches. The computational result indicates that NRM1 method is capable in solving the standard unconstrained optimization problems used. On the other hand, the NRM1 method performs better under inexact line search compared with exact line search.
Energy Technology Data Exchange (ETDEWEB)
Vicroy, D.D.; Knox, C.E.
1983-05-01
A simplified flight management descent algorithm was developed and programmed on a small programmable calculator. It was designed to aid the pilot in planning and executing a fuel conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The algorithm may also be used for planning fuel conservative descents when time is not a consideration. The descent path was calculated for a constant Mach/airspeed schedule from linear approximations of airplane performance with considerations given for gross weight, wind, and nonstandard temperature effects. The flight management descent algorithm and the vertical performance modeling required for the DC-10 airplane is described.
Vicroy, D. D.; Knox, C. E.
1983-01-01
A simplified flight management descent algorithm was developed and programmed on a small programmable calculator. It was designed to aid the pilot in planning and executing a fuel conservative descent to arrive at a metering fix at a time designated by the air traffic control system. The algorithm may also be used for planning fuel conservative descents when time is not a consideration. The descent path was calculated for a constant Mach/airspeed schedule from linear approximations of airplane performance with considerations given for gross weight, wind, and nonstandard temperature effects. The flight management descent algorithm and the vertical performance modeling required for the DC-10 airplane is described.
Salman, Afan Galih
2011-01-01
Penggunaan teknologi di bidang Artificial Intellegence khususnya teknologi Jaringan Syaraf Tiruan (JST) dalampendugaan curah hujan dapat dilakukan dengan metoda pendekatan pembelajaran. Berdasarkan kemampuanbelajar yang dimilikinya, maka JST dapat dilatih untuk mempelajari dan menganalisa pola data masa lalu danberusaha mencari suatu formula atau fungsi yang akan menghubungkan pola data masa lalu dengan keluaranyang diinginkan pada saat ini. Keakuratan hasil prediksi JST diukur berdasarkan ko...
Chen, Jun; Bushman, Frederic D; Lewis, James D; Wu, Gary D; Li, Hongzhe
2013-04-01
Motivated by studying the association between nutrient intake and human gut microbiome composition, we developed a method for structure-constrained sparse canonical correlation analysis (ssCCA) in a high-dimensional setting. ssCCA takes into account the phylogenetic relationships among bacteria, which provides important prior knowledge on evolutionary relationships among bacterial taxa. Our ssCCA formulation utilizes a phylogenetic structure-constrained penalty function to impose certain smoothness on the linear coefficients according to the phylogenetic relationships among the taxa. An efficient coordinate descent algorithm is developed for optimization. A human gut microbiome data set is used to illustrate this method. Both simulations and real data applications show that ssCCA performs better than the standard sparse CCA in identifying meaningful variables when there are structures in the data.
Sympletic quantization of constrained systems
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J.; Wotzasek, C. (Inst. de Fisica, Univ. Federal do Rio de Janeiro, Caixa Postal 68528, 21945 Rio de Janeiro (BR))
1992-06-21
In this paper it is shown that the symplectic two-form, which defines the geometrical structure of a constrained theory in the Faddeev-Jackiw approach, may be brought into a non-degenerated form, by an iterative implementation of the existing constraints. The resulting generalized brackets coincide with those obtained by the Dirac bracket approach, if the constrained system under investigation presents only second-class constraints. For gauge theories, a symmetry breaking term must be supplemented to bring the symplectic form into a non-singular configuration. At present, the singular symplectic two-form provides directly the generators of the time independent gauge transformations.
National Aeronautics and Space Administration — The landing of the Mars Science Laboratory represents the upper limit of current Entry, Descent, and Landing (EDL) capabilities for Mars exploration. The succession...
An Enhanced Modular Terminal Descent Sensor for Landing on Planetary Bodies, Phase I
National Aeronautics and Space Administration — Remote Sensing Solutions (RSS) proposes to fill a critical niche in Entry, Descent, and Landing with the design and subsequent development of a terrain relative...
Intelligent Data Understanding for Architecture Analysis of Entry, Descent, and Landing
National Aeronautics and Space Administration — Because Entry, Descent and Landing (EDL) system validations are limited in Earth environments, these technologies rely heavily on models and analysis tools to...
Mars 2020 Entry, Descent and Landing Instrumentation (MEDLI2)
Bose, Deepak; Wright, Henry; White, Todd; Schoenenberger, Mark; Santos, Jose; Karlgaard, Chris; Kuhl, Chris; Oishi, TOmo; Trombetta, Dominic
2016-01-01
This paper will introduce Mars Entry Descent and Landing Instrumentation (MEDLI2) on NASA's Mars2020 mission. Mars2020 is a flagship NASA mission with science and technology objectives to help answer questions about possibility of life on Mars as well as to demonstrate technologies for future human expedition. Mars2020 is scheduled for launch in 2020. MEDLI2 is a suite of instruments embedded in the heatshield and backshell thermal protection systems of Mars2020 entry vehicle. The objectives of MEDLI2 are to gather critical aerodynamics, aerothermodynamics and TPS performance data during EDL phase of the mission. MEDLI2 builds up the success of MEDLI flight instrumentation on Mars Science Laboratory mission in 2012. MEDLI instrumentation suite measured surface pressure and TPS temperature on the heatshield during MSL entry into Mars. MEDLI data has since been used for unprecedented reconstruction of aerodynamic drag, vehicle attitude, in-situ atmospheric density, aerothermal heating, transition to turbulence, in-depth TPS performance and TPS ablation. [1,2] In addition to validating predictive models, MEDLI data has highlighted extra margin available in the MSL forebody TPS, which can potentially be used to reduce vehicle parasitic mass. MEDLI2 expands the scope of instrumentation by focusing on quantities of interest not addressed in MEDLI suite. The type the sensors are expanded and their layout on the TPS modified to meet these new objectives. The paper will provide key motivation and governing requirements that drive the choice and the implementation of the new sensor suite. The implementation considerations of sensor selection, qualification, and demonstration of minimal risk to the host mission will be described. The additional challenges associated with mechanical accommodation, electrical impact, data storage and retrieval for MEDLI2 system, which extends sensors to backshell will also be described.
Travelling gradient thermocouple calibration
International Nuclear Information System (INIS)
Broomfield, G.H.
1975-01-01
A short discussion of the origins of the thermocouple EMF is used to re-introduce the idea that the Peltier and Thompson effects are indistinguishable from one another. Thermocouples may be viewed as devices which generate an EMF at junctions or as integrators of EMF's developed in thermal gradients. The thermal gradient view is considered the more appropriate, because of its better accord with theory and behaviour, the correct approach to calibration, and investigation of service effects is immediately obvious. Inhomogeneities arise in thermocouples during manufacture and in service. The results of travelling gradient measurements are used to show that such effects are revealed with a resolution which depends on the length of the gradient although they may be masked during simple immersion calibration. Proposed tests on thermocouples irradiated in a nuclear reactor are discussed
Gradient Alloy for Optical Packaging
National Aeronautics and Space Administration — Advances in additive manufacturing, such as Laser Engineered Net Shaping (LENS), enables the fabrication of compositionally gradient microstructures, i.e. gradient...
Aerodynamics of Reentry Vehicle Clipper at Descent Phase
Semenov, Yu. P.; Reshetin, A. G.; Dyadkin, A. A.; Petrov, N. K.; Simakova, T. V.; Tokarev, V. A.
2005-02-01
From Gagarin spacecraft to reusable orbiter Buran, RSC Energia has traveled a long way in the search for the most optimal and, which is no less important, the most reliable spacecraft for manned space flight. During the forty years of space exploration, in cooperation with a broad base of subcontractors, a number of problems have been solved which assure a safe long stay in space. Vostok and Voskhod spacecraft were replaced with Soyuz supporting a crew of three. During missions to a space station, it provides crew rescue capability in case of a space station emergency at all times (the spacecraft life is 200 days).The latest modification of Soyuz spacecraft -Soyuz TMA -in contrast to its predecessors, allows to become a space flight participant to a person of virtually any anthropometric parameters with a mass of 50 to 95 kg capable of withstanding up to 6 g load during descent. At present, Soyuz TMA spacecraft are the state-of-the-art, reliable and only means of the ISS crew delivery, in-flight support and return. Introduced on the basis of many years of experience in operation of manned spacecraft were not only the principles of deep redundancy of on-board systems and equipment, but, to assure the main task of the spacecraft -the crew return to Earth -the principles of functional redundancy. That is, vital operations can be performed by different systems based on different physical principles. The emergency escape system that was developed is the only one in the world that provides crew rescue in case of LV failure at any phase in its flight. Several generations of space stations that have been developed have broadened, virtually beyond all limits, capabilities of man in space. The docking system developed at RSC Energia allowed not only to dock spacecraft in space, but also to construct in orbit various complex space systems. These include large space stations, and may include in the future the in-orbit construction of systems for the exploration of the Moon and
Pedestrian ascent and descent fundamental diagram on stairway
Chen, Juan; Lo, S. M.; Ma, Jian
2017-08-01
Due to the interaction among individuals, pedestrian walking speeds in relatively dense crowds when descending and ascending stairs may present different features from a single pedestrian moving freely. Thus, to obtain a large range of densities, a series of single-file pedestrian movement experiments under laboratory conditions were performed. The trends of the fundamental diagram in a wide pedestrian density range for staircase movement are captured. Detailed features of pedestrian speed with the increase of pedestrian density, headway, and the influence of pedestrians’ lateral sway are further discussed. It is found that with the increase of pedestrian density, the speed decrease rate varies. Meanwhile, the decrease of headway, leads to two speed regimes, i.e. free movement and linear constrained movement. We show that pedestrian speed can be described by counting the number of steps separating pedestrians in longitudinal direction. These enrichments can benefit pedestrian modelling and improve the evaluation of the evacuation performance of a staircase.
Trends in PDE constrained optimization
Benner, Peter; Engell, Sebastian; Griewank, Andreas; Harbrecht, Helmut; Hinze, Michael; Rannacher, Rolf; Ulbrich, Stefan
2014-01-01
Optimization problems subject to constraints governed by partial differential equations (PDEs) are among the most challenging problems in the context of industrial, economical and medical applications. Almost the entire range of problems in this field of research was studied and further explored as part of the Deutsche Forschungsgemeinschaft (DFG) priority program 1253 on “Optimization with Partial Differential Equations” from 2006 to 2013. The investigations were motivated by the fascinating potential applications and challenging mathematical problems that arise in the field of PDE constrained optimization. New analytic and algorithmic paradigms have been developed, implemented and validated in the context of real-world applications. In this special volume, contributions from more than fifteen German universities combine the results of this interdisciplinary program with a focus on applied mathematics. The book is divided into five sections on “Constrained Optimization, Identification and Control”...
Constraining spacetime torsion with LAGEOS
March, Riccardo; Bellettini, Giovanni; Tauraso, Roberto; Dell'Agnello, Simone
2011-11-01
We compute the corrections to the orbital Lense-Thirring effect (or frame-dragging) in the presence of spacetime torsion. We analyze the motion of a test body in the gravitational field of a rotating axisymmetric massive body, using the parametrized framework of Mao, Tegmark, Guth and Cabi. In the cases of autoparallel and extremal trajectories, we derive the specific approximate expression of the corresponding system of ordinary differential equations, which are then solved with methods of Celestial Mechanics. We calculate the secular variations of the longitudes of the node and of the pericenter. We also show how the LAser GEOdynamics Satellites (LAGEOS) can be used to constrain torsion parameters. We report the experimental constraints obtained using both the nodes and perigee measurements of the orbital Lense-Thirring effect. This makes LAGEOS and Gravity Probe B complementary frame-dragging and torsion experiments, since they constrain three different combinations of torsion parameters.
A Globally Convergent Matrix-Free Method for Constrained Equations and Its Linear Convergence Rate
Directory of Open Access Journals (Sweden)
Min Sun
2014-01-01
Full Text Available A matrix-free method for constrained equations is proposed, which is a combination of the well-known PRP (Polak-Ribière-Polyak conjugate gradient method and the famous hyperplane projection method. The new method is not only derivative-free, but also completely matrix-free, and consequently, it can be applied to solve large-scale constrained equations. We obtain global convergence of the new method without any differentiability requirement on the constrained equations. Compared with the existing gradient methods for solving such problem, the new method possesses linear convergence rate under standard conditions, and a relax factor γ is attached in the update step to accelerate convergence. Preliminary numerical results show that it is promising in practice.
Directory of Open Access Journals (Sweden)
Massimo Giovannini
2015-06-01
Full Text Available Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.
Giovannini, Massimo
2015-01-01
Cosmological singularities are often discussed by means of a gradient expansion that can also describe, during a quasi-de Sitter phase, the progressive suppression of curvature inhomogeneities. While the inflationary event horizon is being formed the two mentioned regimes coexist and a uniform expansion can be conceived and applied to the evolution of spatial gradients across the protoinflationary boundary. It is argued that conventional arguments addressing the preinflationary initial conditions are necessary but generally not sufficient to guarantee a homogeneous onset of the conventional inflationary stage.
High gradient superconducting quadrupoles
International Nuclear Information System (INIS)
Lundy, R.A.; Brown, B.C.; Carson, J.A.; Fisk, H.E.; Hanft, R.H.; Mantsch, P.M.; McInturff, A.D.; Remsbottom, R.H.
1987-07-01
Prototype superconducting quadrupoles with a 5 cm aperture and gradient of 16 kG/cm have been built and tested as candidate magnets for the final focus at SLC. The magnets are made from NbTi Tevatron style cable with 10 inner and 14 outer turns per quadrant. Quench performance and multipole data are presented. Design and data for a low current, high gradient quadrupole, similar in cross section but wound with a cable consisting of five insulated conductors are also discussed
Tracer-Based Determination of Vortex Descent in the 1999-2000 Arctic Winter
Greenblatt, Jeffery B.; Jost, Hans-Juerg; Loewenstein, Max; Podolske, James R.; Hurst, Dale F.; Elkins, James W.; Schauffler, Sue M.; Atlas, Elliot L.; Herman, Robert L.; Webster, Christopher R.
2001-01-01
A detailed analysis of available in situ and remotely sensed N2O and CH4 data measured in the 1999-2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (theta) among balloon and aircraft vertical profiles (an average of 19-23 K on a given N2O or CH4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for November 26, 1999, whose error bars encompassed the observed variability. High-latitude, extravortex profiles measured in different years and seasons revealed substantial variability in N2O and CH4 on theta surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex-vortex differences, we inferred descent prior to November 26: 397+/-15 K (1sigma) at 30 ppbv N2O and 640 ppbv CH4, and 28+/-13 K above 200 ppbv N2O and 1280 ppbv CH4. Changes in theta were determined on five N2O and CH4 isopleths from November 26 through March 12, and descent rates were calculated on each N2O isopleth for several time intervals. The maximum descent rates were seen between November 26 and January 27: 0.82+/-0.20 K/day averaged over 50-250 ppbv N2O. By late winter (February 26-March 12), the average rate had decreased to 0.10+/-0.25 K/day. Descent rates also decreased with increasing N2O; the winter average (November 26-March 5) descent rate varied from 0.75+/-0.10 K/day at 50 ppbv to 0.40+/-0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999-2000 vortex descent, SLIMCAT and REPROBUS, despite theta offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very favorably with the inferred rates from observation.
Tracer-based Determination of Vortex Descent in the 1999/2000 Arctic Winter
Greenblatt, Jeffrey B.; Jost, Hans-Juerg; Loewenstein, Max; Podolske, James R.; Hurst, Dale F.; Elkins, James W.; Schauffler, Sue M.; Atlas, Elliot L.; Herman, Robert L.; Webster, Chrisotopher R.
2002-01-01
A detailed analysis of available in situ and remotely sensed N2O and CH4 data measured in the 1999/2000 winter Arctic vortex has been performed in order to quantify the temporal evolution of vortex descent. Differences in potential temperature (theta) among balloon and aircraft vertical profiles (an average of 19-23 K on a given N2O or CH4 isopleth) indicated significant vortex inhomogeneity in late fall as compared with late winter profiles. A composite fall vortex profile was constructed for 26 November 1999, whose error bars encompassed the observed variability. High-latitude extravortex profiles measured in different years and seasons revealed substantial variability in N2O and CH4 on theta surfaces, but all were clearly distinguishable from the first vortex profiles measured in late fall 1999. From these extravortex-vortex differences we inferred descent prior to 26 November: as much as 397 plus or minus 15 K (lsigma) at 30 ppbv N2O and 640 ppbv CH4, and falling to 28 plus or minus 13 K above 200 ppbv N2O and 1280 ppbv CH4. Changes in theta were determined on five N2O and CH4 isopleths from 26 November through 12 March, and descent rates were calculated on each N2O isopleth for several time intervals. The maximum descent rates were seen between 26 November and 27 January: 0.82 plus or minus 0.20 K/day averaged over 50- 250 ppbv N2O. By late winter (26 February to 12 March), the average rate had decreased to 0.10 plus or minus 0.25 K/day. Descent rates also decreased with increasing N2O; the winter average (26 November to 5 March) descent rate varied from 0.75 plus or minus 0.10 K/day at 50 ppbv to 0.40 plus or minus 0.11 K/day at 250 ppbv. Comparison of these results with observations and models of descent in prior years showed very good overall agreement. Two models of the 1999/2000 vortex descent, SLIMCAT and REPROBUS, despite theta offsets with respect to observed profiles of up to 20 K on most tracer isopleths, produced descent rates that agreed very
Directory of Open Access Journals (Sweden)
Timothy R. Rebbeck
2013-01-01
Full Text Available Prostate cancer (CaP is the leading cancer among men of African descent in the USA, Caribbean, and Sub-Saharan Africa (SSA. The estimated number of CaP deaths in SSA during 2008 was more than five times that among African Americans and is expected to double in Africa by 2030. We summarize publicly available CaP data and collected data from the men of African descent and Carcinoma of the Prostate (MADCaP Consortium and the African Caribbean Cancer Consortium (AC3 to evaluate CaP incidence and mortality in men of African descent worldwide. CaP incidence and mortality are highest in men of African descent in the USA and the Caribbean. Tumor stage and grade were highest in SSA. We report a higher proportion of T1 stage prostate tumors in countries with greater percent gross domestic product spent on health care and physicians per 100,000 persons. We also observed that regions with a higher proportion of advanced tumors reported lower mortality rates. This finding suggests that CaP is underdiagnosed and/or underreported in SSA men. Nonetheless, CaP incidence and mortality represent a significant public health problem in men of African descent around the world.
Entry, Descent, and Landing Performance for a Mid-Lift-to-Drag Ratio Vehicle at Mars
Johnson, Breanna J.; Braden, Ellen M.; Sostaric, Ronald R.; Cerimele, Christopher J.; Lu, Ping
2018-01-01
In an effort to mature the design of the Mid-Lift-to-Drag ratio Rigid Vehicle (MRV) candidate of the NASA Evolvable Mars Campaign (EMC) architecture study, end-to-end six-degree-of-freedom (6DOF) simulations are needed to ensure a successful entry, descent, and landing (EDL) design. The EMC study is assessing different vehicle and mission architectures to determine which candidate would be best to deliver a 20 metric ton payload to the surface of Mars. Due to the large mass payload and the relatively low atmospheric density of Mars, all candidates of the EMC study propose to use Supersonic Retro-Propulsion (SRP) throughout the descent and landing phase, as opposed to parachutes, in order to decelerate to a subsonic touchdown. This paper presents a 6DOF entry-to-landing performance and controllability study with sensitivities to dispersions, particularly in the powered descent and landing phases.
Convective descent simulations of drilling discharges on Georges and Sable Island banks
International Nuclear Information System (INIS)
Andrade, Y.; Loder, J.W.
1997-01-01
Factors affecting the fate of drilling mud discharges on Georges and Sable Island Banks were examined. The Koh and Chang jet discharge model was used to simulate the convective descent of a jet discharge of relatively dense materials at sites representing different hydrographic and depth regimes with a range of mud densities, and different discharge configurations, ocean currents and seasonal stratifications. The study revealed the dependence of the depth of descent and properties of the discharge plume on the discharge configuration and oceanographic conditions. The factors that affected the depth of descent were mud density, depth of release, initial downward volume flux of the discharge, current strength and ocean stratification. 22 refs., 3 tabs., 59 figs
Videodefaecography combined with measurement of the anorectal angle and of perineal descent
International Nuclear Information System (INIS)
Skomorowska, E.; Henrichsen, S.; Christiansen, J.; Hegedues, V.; Glostrup Sygehus, Copenhagen
1987-01-01
Cineradiographic defaecography combined with measurement of the anorectal angle and descent of the pelvic floor is proposed. The method used in 73 women gave valuable information in 48 patients who complained of anal incompetence, rectal tenesmus, and chronic constipation. In these patients, high and low rectal intussusception, rectocele, and pathologic movement of the pelvic floor were detected. Some of these phenomena could only be diagnosed by the radiologic method here described. Quantitations of the anorectal angle and descent of the pelvic floor placed the group with constipation halfway between normal individuals and those with anal incompetence. The value of this finding is discussed. Recent improvements in anorectal surgery often make videodefaecography decisive for the choice of the optimal operative method. Therefore, videodefaecography together with measurement of the anorectal angle and pelvic floor descent is recommended whenever anorectal surgery for correction of functional disturbances is contemplated. (orig.)
A Task-Analytic Approach to the Determination of Training Requirements for the Precision Descent
Smith, Nancy; Rosekind, Mark (Technical Monitor)
1996-01-01
A task-analytic approach was used to evaluate the results from an experiment comparing two training methods for the "Precision Descent," a cockpit procedure designed to complement a new, computer-based air traffic control advisory system by allowing air traffic controllers to assign precise descent trajectories to aircraft. A task model was developed for the procedure using a methodology that represents four different categories of task-related knowledge: (1) ability to determine current flight goals; (2) ability to assess the current flight situation relative to those goals; (3) operational knowledge about flight-related tasks; and (4) knowledge about task selection. This model showed what knowledge experienced pilots already possessed, and how that knowledge was supplemented by training material provided in the two training conditions. All flight crews were given a "Precision Descent Chart" that explained the procedure's clearances and compliance requirements. This information enabled pilots to establish appropriate flight goals for the descent, and to monitor their compliance with those goals. In addition to this chart, half of the crews received a "Precision Descent Bulletin" containing technique recommendations for performing procedure-related tasks. The Bulletin's recommendations supported pilots in task selection and helped clarify the procedure's compliance requirements. Eight type-rated flight crews flew eight Precision Descents in a Boeing 747-400 simulator, with four crews in each of the two training conditions. Both conditions (Chart and Chart-with-Bulletin) relied exclusively on the use of those documents to introduce the procedure. No performance feedback was provided during the experiment. Preliminary result show better procedure compliance and higher acceptability ratings from flight crews in the Chart-with-Bulletin condition. These crews performed flight-related tasks less efficiently, however, using the simpler but less efficient methods suggested
Pizzoferrato, Anne-Cécile; Fauconnier, Arnaud; Bader, Georges; de Tayrac, Renaud; Fort, Julie; Fritel, Xavier
2016-07-01
Obstetric trauma during childbirth is considered a major risk factor for postpartum urinary incontinence (UI), particularly stress urinary incontinence. Our aim was to investigate the relation between postpartum UI, mode of delivery, and urethral descent, and to define a group of women who are particularly at risk of postnatal UI. A total of 186 women were included their first pregnancy. Validated questionnaires about urinary symptoms during pregnancy, 2 and 12 months after delivery, were administered. Urethral descent was assessed clinically and by ultrasound at inclusion. Multivariate logistic regression analysis was used to determine the risk factors for UI during pregnancy, at 2 months and 1 year after first delivery. The prevalence of UI was 38.6, 46.5, 35.6, and 34.4 % at inclusion, late pregnancy, 2 months postpartum, and 1 year postpartum respectively. No significant association was found between UI at late pregnancy and urethral descent assessed clinically or by ultrasound. The only risk factor for UI at 2 months postpartum was UI at inclusion (OR 6.27 [95 % CI 2.70-14.6]). The risk factors for UI at 1 year postpartum were UI at inclusion (6.14 [2.22-16.9]), body mass index (BMI), and urethral descent at inclusion, assessed clinically (7.21 [2.20-23.7]) or by ultrasound. The mode of delivery was not associated with urethral descent. Prenatal urethral descent and UI during pregnancy are risk factors for UI at 1 year postpartum. These results indicate that postnatal UI is more strongly influenced by susceptibility factors existing before first delivery than by the mode of delivery.
Evolutionary analyses of non-genealogical bonds produced by introgressive descent.
Bapteste, Eric; Lopez, Philippe; Bouchard, Frédéric; Baquero, Fernando; McInerney, James O; Burian, Richard M
2012-11-06
All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity.
Eye Movement Patterns of the Elderly during Stair Descent:Effect of Illumination
Kasahara, Satoko; Okabe, Sonoko; Nakazato, Naoko; Ohno, Yuko
The relationship between the eye movement pattern during stair descent and illumination was studied in 4 elderly people in comparison with that in 5 young people. The illumination condition was light (85.0±30.9 lx) or dark (0.7±0.3 lx), and data of eye movements were obtained using an eye mark recorder. A flight of 15 steps was used for the experiment, and data on 3 steps in the middle, on which the descent movements were stabilized, were analyzed. The elderly subjects pointed their eyes mostly directly in front in the facial direction regardless of the illumination condition, but the young subjects tended to look down under the light condition. The young subjects are considered to have confirmed the safety of the front by peripheral vision, checked the stepping surface by central vision, and still maintained the upright position without leaning forward during stair descent. The elderly subjects, in contrast, always looked at the visual target by central vision even under the light condition and leaned forward. The range of eye movements was larger vertically than horizontally in both groups, and a characteristic eye movement pattern of repeating a vertical shuttle movement synchronous with descent of each step was observed. Under the dark condition, the young subjects widened the range of vertical eye movements and reduced duration of fixation. The elderly subjects showed no change in the range of eye movements but increased duration of fixation during stair descent. These differences in the eye movements are considered to be compensatory reactions to narrowing of the vertical visual field, reduced dark adaptation, and reduced dynamic visual acuity due to aging. These characteristics of eye movements of the elderly lead to an anteriorly leaned posture and lack of attention to the front during stair descent.
Coherent states in constrained systems
International Nuclear Information System (INIS)
Nakamura, M.; Kojima, K.
2001-01-01
When quantizing the constrained systems, there often arise the quantum corrections due to the non-commutativity in the re-ordering of constraint operators in the products of operators. In the bosonic second-class constraints, furthermore, the quantum corrections caused by the uncertainty principle should be taken into account. In order to treat these corrections simultaneously, the alternative projection technique of operators is proposed by introducing the available minimal uncertainty states of the constraint operators. Using this projection technique together with the projection operator method (POM), these two kinds of quantum corrections were investigated
Constrained minimization in C ++ environment
International Nuclear Information System (INIS)
Dymov, S.N.; Kurbatov, V.S.; Silin, I.N.; Yashchenko, S.V.
1998-01-01
Based on the ideas, proposed by one of the authors (I.N.Silin), the suitable software was developed for constrained data fitting. Constraints may be of the arbitrary type: equalities and inequalities. The simplest of possible ways was used. Widely known program FUMILI was realized to the C ++ language. Constraints in the form of inequalities φ (θ i ) ≥ a were taken into account by change into equalities φ (θ i ) = t and simple inequalities of type t ≥ a. The equalities were taken into account by means of quadratic penalty functions. The suitable software was tested on the model data of the ANKE setup (COSY accelerator, Forschungszentrum Juelich, Germany)
Constraining walking and custodial technicolor
DEFF Research Database (Denmark)
Foadi, Roshan; Frandsen, Mads Toudal; Sannino, Francesco
2008-01-01
We show how to constrain the physical spectrum of walking technicolor models via precision measurements and modified Weinberg sum rules. We also study models possessing a custodial symmetry for the S parameter at the effective Lagrangian level-custodial technicolor-and argue that these models...... cannot emerge from walking-type dynamics. We suggest that it is possible to have a very light spin-one axial (vector) boson. However, in the walking dynamics the associated vector boson is heavy while it is degenerate with the axial in custodial technicolor Udgivelsesdato: 19 May...
The Elastochrone: the descent time of a sphere on a flexible beam
Aristoff, Jeffrey; Clanet, Christophe; Bush, John
2009-03-01
We present the results of a combined experimental and theoretical investigation of the motion of a sphere on an inclined flexible beam. A theoretical model is developed to describe the dynamics, and in the limit where the beam reacts instantaneously to the loading, we obtain exact solutions for the load trajectory and descent time. For the case of an initially horizontal beam, we calculate the period of the resulting oscillations. Theoretical predictions compare favorably with our experimental observations in this quasi-static regime. The time taken for descent along an elastic beam, the elastochrone, is compared to the classical brachistochrone, the shortest time between two points in a gravitational field.
Park, Cheol; Glaser, Matt; Maclennan, Joe; Clark, Noel; Trittel, Torsten; Stannarius, Ralf
Freely-suspended smectic films of sub-micrometer thickness and lateral extensions of several millimeters were used to study thermally driven migration and convection in the film plane. Film experiments were performed during the 6 minute microgravity phase of a TEXUS suborbital rocket flight (Texus 52, launched April 27, 2015). We have found an attraction of the smectic material towards the cold edge of the film in a temperature gradient, similar to the Soret effect. This process is reversed when this edge is heated up again. Thermal convection driven by two thermocontacts in the film is practically absent, even at temperature gradients up to 10 K/mm, with thermally driven convection only setting in when the hot post reaches the transition temperature to the nematic phase. The Observation and Analysis of Smectic Islands in Space (OASIS) flight hardware was launched on SpaceX-6 in April 2015 and experiments on smectic bubbles were carried out on the International Space Station using four different smectic A and C liquid crystal materials in separate sample chambers. We observed that smectic islands on the surface of the bubbles migrated towards the colder part of the bubble in a temperature gradient. This work was supported by NASA Grant No. NNX-13AQ81G, by the Soft Materials Research Center under NSF MRSEC Grants No. DMR-0820579 and No. DMR-1420736, and by DLR Grants 50WM1127 and 50WM1430.
Eigen-Gradients for Traffic Sign Recognition
Directory of Open Access Journals (Sweden)
Sheila Esmeralda Gonzalez-Reyna
2013-01-01
Full Text Available Traffic sign detection and recognition systems include a variety of applications like autonomous driving, road sign inventory, and driver support systems. Machine learning algorithms provide useful tools for traffic sign identification tasks. However, classification algorithms depend on the preprocessing stage to obtain high accuracy rates. This paper proposes a road sign characterization method based on oriented gradient maps and the Karhunen-Loeve transform in order to improve classification performance. Dimensionality reduction may be important for portable applications on resource constrained devices like FPGAs; therefore, our approach focuses on achieving a good classification accuracy by using a reduced amount of attributes compared to some state-of-the-art methods. The proposed method was tested using German Traffic Sign Recognition Benchmark, reaching a dimensionality reduction of 99.3% and a classification accuracy of 95.9% with a Multi-Layer Perceptron.
Bulk diffusion in a kinetically constrained lattice gas
Arita, Chikashi; Krapivsky, P. L.; Mallick, Kirone
2018-03-01
In the hydrodynamic regime, the evolution of a stochastic lattice gas with symmetric hopping rules is described by a diffusion equation with density-dependent diffusion coefficient encapsulating all microscopic details of the dynamics. This diffusion coefficient is, in principle, determined by a Green–Kubo formula. In practice, even when the equilibrium properties of a lattice gas are analytically known, the diffusion coefficient cannot be computed except when a lattice gas additionally satisfies the gradient condition. We develop a procedure to systematically obtain analytical approximations for the diffusion coefficient for non-gradient lattice gases with known equilibrium. The method relies on a variational formula found by Varadhan and Spohn which is a version of the Green–Kubo formula particularly suitable for diffusive lattice gases. Restricting the variational formula to finite-dimensional sub-spaces allows one to perform the minimization and gives upper bounds for the diffusion coefficient. We apply this approach to a kinetically constrained non-gradient lattice gas in two dimensions, viz. to the Kob–Andersen model on the square lattice.
Directory of Open Access Journals (Sweden)
Güzelcan Yener
2009-08-01
Full Text Available Abstract Background Studies have shown a clear relationship between depressive disorders and vitamin B12 deficiency. Gastroenteritis and Helicobacter pylori infections can cause vitamin B12 deficiency. Helicobacter pylori infections are not uncommon among people of Turkish descent in The Netherlands. Aim To examine the frequency of vitamin B12 deficiency in depressive patients of Turkish descent and compare it to the frequency of vitamin B12 deficiency in depressive patients of Dutch descent. Methods The present study is a comparative cross-sectional study of 47 patients of Turkish descent and 28 of Dutch descent. The depressive disorder diagnosis and differential diagnosis were made using the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, fourth edition text revision (SCID. The severity of the depressive symptoms was determined using the Beck Depression Inventory (BDI and the 21-item Hamilton Depression Rating Scale (HAM-D-21. Serum baseline vitamin B6 and B12, folic acid and total serum homocysteine (tHcy levels were measured. Results The average ages of the patients of Turkish and Dutch descent were 40.57 and 44.75 years, respectively. There were no demonstrable differences between the serum vitamin B6, folic acid and tHcy levels in the two groups. The serum vitamin B12 levels were however clearly lower in the patients of Turkish descent than in those of Dutch descent. Vitamin B12 deficiency was however observed in 14 patients of Turkish descent and 1 of Dutch descent. This difference was significant. On the BDI, the patients of Turkish descent scored significantly higher than those of Dutch descent. Patients with vitamin B12 deficiency and those with hyperhomocysteinaemia had a significantly higher BDI score than patients with normal vitamin B12 and homocysteine levels. No relationship was observed with vitamin B12 and tHcy. Conclusion Vitamin B12 deficiency occurs more frequently in depressive
Güzelcan, Yener; van Loon, Peter
2009-08-13
Studies have shown a clear relationship between depressive disorders and vitamin B12 deficiency. Gastroenteritis and Helicobacter pylori infections can cause vitamin B12 deficiency. Helicobacter pylori infections are not uncommon among people of Turkish descent in The Netherlands. To examine the frequency of vitamin B12 deficiency in depressive patients of Turkish descent and compare it to the frequency of vitamin B12 deficiency in depressive patients of Dutch descent. The present study is a comparative cross-sectional study of 47 patients of Turkish descent and 28 of Dutch descent. The depressive disorder diagnosis and differential diagnosis were made using the Structured Clinical Interview for the Diagnostic and Statistical Manual of Mental Disorders, fourth edition text revision (SCID). The severity of the depressive symptoms was determined using the Beck Depression Inventory (BDI) and the 21-item Hamilton Depression Rating Scale (HAM-D-21). Serum baseline vitamin B6 and B12, folic acid and total serum homocysteine (tHcy) levels were measured. The average ages of the patients of Turkish and Dutch descent were 40.57 and 44.75 years, respectively. There were no demonstrable differences between the serum vitamin B6, folic acid and tHcy levels in the two groups. The serum vitamin B12 levels were however clearly lower in the patients of Turkish descent than in those of Dutch descent. Vitamin B12 deficiency was however observed in 14 patients of Turkish descent and 1 of Dutch descent. This difference was significant. On the BDI, the patients of Turkish descent scored significantly higher than those of Dutch descent. Patients with vitamin B12 deficiency and those with hyperhomocysteinaemia had a significantly higher BDI score than patients with normal vitamin B12 and homocysteine levels. No relationship was observed with vitamin B12 and tHcy. Vitamin B12 deficiency occurs more frequently in depressive patients of Turkish than of Dutch descent. This is why it is
Genome-wide association study of kidney function decline in individuals of European descent
Gorski, Mathias; Tin, Adrienne; Garnaas, Maija; McMahon, Gearoid M.; Chu, Audrey Y.; Tayo, Bamidele O.; Pattaro, Cristian; Teumer, Alexander; Chasman, Daniel I.; Chalmers, John; Hamet, Pavel; Tremblay, Johanne; Woodward, Marc; Aspelund, Thor; Eiriksdottir, Gudny; Gudnason, Vilmundur; Harris, Tamara B.; Launer, Lenore J.; Smith, Albert V.; Mitchell, Braxton D.; O'Connell, Jeffrey R.; Shuldiner, Alan R.; Coresh, Josef; Li, Man; Freudenberger, Paul; Hofer, Edith; Schmidt, Helena; Schmidt, Reinhold; Holliday, Elizabeth G.; Mitchell, Paul; Wang, Jie Jin; de Boer, Ian H.; Li, Guo; Siscovick, David S.; Kutalik, Zoltan; Corre, Tanguy; Vollenweider, Peter; Waeber, Gerard; Gupta, Jayanta; Kanetsky, Peter A.; Hwang, Shih-Jen; Olden, Matthias; Yang, Qiong; de Andrade, Mariza; Atkinson, Elizabeth J.; Kardia, Sharon L. R.; Turner, Stephen T.; Stafford, Jeanette M.; Ding, Jingzhong; Liu, Yongmei; Barlassina, Cristina; Cusi, Daniele; Salvi, Erika; Staessen, Jan A.; Ridker, Paul M.; Grallert, Harald; Meisinger, Christa; Mueller-Nurasyid, Martina; Kraemer, Bernhard K.; Kramer, Holly; Rosas, Sylvia E.; Nolte, Ilja M.; Penninx, Brenda W.; Snieder, Harold; Del Greco, M. Fabiola; Franke, Andre; Noethlings, Ute; Lieb, Wolfgang; Bakker, Stephan J. L.; Gansevoort, Ron T.; van der Harst, Pim; Dehghan, Abbas; Franco, Oscar H.; Hofman, Albert; Rivadeneira, Fernando; Sedaghat, Sanaz; Uitterlinden, Andre G.; Coassin, Stefan; Haun, Margot; Kollerits, Barbara; Kronenberg, Florian; Paulweber, Bernhard; Aumann, Nicole; Endlich, Karlhans; Pietzner, Mike; Voelker, Uwe; Rettig, Rainer; Chouraki, Vincent; Helmer, Catherine; Lambert, Jean-Charles; Metzger, Marie; Stengel, Benedicte; Lehtimaki, Terho; Lyytikainen, Leo-Pekka; Raitakari, Olli; Johnson, Andrew; Parsa, Afshin; Bochud, Murielle; Heid, Iris M.; Goessling, Wolfram; Kottgen, Anna; Kao, W. H. Linda; Fox, Caroline S.; Boeger, Carsten A.
Genome-wide association studies (GWASs) have identified multiple loci associated with cross-sectional eGFR, but a systematic genetic analysis of kidney function decline over time is missing. Here we conducted a GWAS meta-analysis among 63,558 participants of European descent, initially from 16
Genome-wide association study of kidney function decline in individuals of European descent
M. Gorski (Mathias); A. Tin (Adrienne); M. Garnaas (Maija); G.M. McMahon (Gearoid M.); A.Y. Chu (Audrey Y.); B. Tayo (Bamidele); C. Pattaro (Cristian); A. Teumer (Alexander); D.I. Chasman (Daniel); J. Chalmers (John); P. Hamet (Pavel); J. Tremblay (Johanne); M. Woodward (Mark); T. Aspelund (Thor); G. Eiriksdottir (Gudny); V. Gudnason (Vilmundur); T.B. Harris (Tamara); L.J. Launer (Lenore); A.V. Smith (Albert V.); B.D. Mitchell (Braxton); J.R. O´Connell; A.R. Shuldiner (Alan); J. Coresh (Josef); M. Li (Man); P. Freudenberger (Paul); E. Hofer (Edith); R. Schmidt (Reinhold); R. Schmidt (Reinhold); E.G. Holliday (Elizabeth); P. Mitchell (Paul); J.J. Wang (Jie Jin); I.H. de Boer (Ian); G. Li (Guo); D.S. Siscovick (David); Z. Kutalik; T. Corre (Tanguy); P. Vollenweider (Peter); G. Waeber (Gérard); J. Gupta (Jayanta); P.P. Kanetsky (Peter P.); S.J. Hwang; M. Olden (Matthias); Q. Yang (Qiong Fang); M. de Andrade (Mariza); E.J. Atkinson (Elizabeth J.); S.L.R. Kardia (Sharon); S.T. Turner (Stephen); J.M. Stafford (Jeanette M.); J. Ding (Jingzhong); Y. Liu; C. Barlassina (Christina); D. Cusi (Daniele); E. Salvi (Erika); J.A. Staessen (Jan); P.M. Ridker (Paul); H. Grallert (Harald); C. Meisinger (Christa); M. Müller-Nurasyid (Martina); B.K. Krämer (Bernhard K.); H. Kramer (Holly); S.E. Rosas (Sylvia E.); I.M. Nolte (Ilja M.); B.W.J.H. Penninx (Brenda); H. Snieder (Harold); M. Fabiola Del Greco; A. Franke (Andre); U. Nöthlings (Ute); W. Lieb (Wolfgang); S.J.L. Bakker (Stephan); R.T. Gansevoort (Ron); P. Van Der Harst (Pim); A. Dehghan (Abbas); O.H. Franco (Oscar); A. Hofman (Albert); F. Rivadeneira Ramirez (Fernando); S. Sedaghat (Sanaz); A.G. Uitterlinden (André); S. Coassin (Stefan); M. Haun (Margot); B. Kollerits (Barbara); F. Kronenberg (Florian); B. Paulweber (Bernhard); N. Aumann (Nicole); K. Endlich (Karlhans); M. Pietzner (Mike); U. Völker (Uwe); R. Rettig (Rainer); V. Chouraki (Vincent); C. Helmer (Catherine); J.-C. Lambert (Jean-Charles); M. Metzger (Marie); B. Stengel (Benedicte); T. Lehtimäki (Terho); L.-P. Lyytikäinen (Leo-Pekka); O. Raitakari (Olli); A.D. Johnson (Andrew); A. Parsa (Afshin); M. Bochud (Murielle); I.M. Heid (Iris); W. Goessling (Wolfram); A. K̈ttgen (Anna); W.H.L. Kao (Wen); C.S. Fox (Caroline S.); C.A. Böger (Carsten)
2015-01-01
textabstractGenome-wide association studies (GWASs) have identified multiple loci associated with cross-sectional eGFR, but a systematic genetic analysis of kidney function decline over time is missing. Here we conducted a GWAS meta-analysis among 63,558 participants of European descent, initially
Murray, Ashley; Ellis, Monica U.; Castellanos, Ted; Gaul, Zaneta; Sutton, Madeline Y.; Sneed, Carl D.
2014-01-01
We examined approaches used by African-American mothers and mothers of Latino descent for informal sex-related discussions with their children to inform sexually transmitted infection (STI)/HIV intervention development efforts. We recruited mothers (of children aged 12-15) from youth service agencies and a university in southern California.…
Lambert, Anne-Sophie; Bougneres, Pierre
2016-01-01
One third of infants with congenital hypogonadotropic hypogonadism (CHH) are said to have micropenis and/or bilateral or unilateral cryptorchidism leading many of them to orchiopexy. Our previous study in two patients suggests that prolonged subcutaneous infusion of large doses of gonadotropins might normalize testicular function and growth. To confirm the effects of early and prolonged subcutaneous infusion of large doses of gonadotropins on growth and descent of the testes. Eight boys with CHH, aged 0.25-11 months. Testes were non-palpable in 5 or in high scrotal position in 3. CHH was isolated in 5 infants and part of a syndrome of combined pituitary hormonal deficits in the 3 others. In response to gonadotropin infusion, mean levels of testicular hormones were normalized. Complete testis descent occurred in 6 patients. Partial descent occurred in 2. Testes re-ascended in 1 patient. Testes and penis gained normal dimensions in all cases. Subcutaneous gonadotropin infusion seems able to induce testis descent in a large proportion of infants with CHH. If confirmed, this may allow patients to avoid testes surgery but studies in larger series are needed to evaluate the benefits of this treatment versus traditional orchiopexy.
Bagging constrained equity premium predictors
DEFF Research Database (Denmark)
Hillebrand, Eric; Lee, Tae-Hwy; Medeiros, Marcelo
2014-01-01
The literature on excess return prediction has considered a wide array of estimation schemes, among them unrestricted and restricted regression coefficients. We consider bootstrap aggregation (bagging) to smooth parameter restrictions. Two types of restrictions are considered: positivity of the r......The literature on excess return prediction has considered a wide array of estimation schemes, among them unrestricted and restricted regression coefficients. We consider bootstrap aggregation (bagging) to smooth parameter restrictions. Two types of restrictions are considered: positivity...... of the regression coefficient and positivity of the forecast. Bagging constrained estimators can have smaller asymptotic mean-squared prediction errors than forecasts from a restricted model without bagging. Monte Carlo simulations show that forecast gains can be achieved in realistic sample sizes for the stock...... return problem. In an empirical application using the data set of Campbell and Thompson (2008), we show that we can improve the forecast performance further by smoothing the restriction through bagging....
Formal language constrained path problems
Energy Technology Data Exchange (ETDEWEB)
Barrett, C.; Jacob, R.; Marathe, M.
1997-07-08
In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.
Dang, Chuangyin; Liang, Jianqing; Yang, Yang
2013-03-01
A deterministic annealing algorithm is proposed for approximating a solution of the linearly constrained nonconvex quadratic minimization problem. The algorithm is derived from applications of a Hopfield-type barrier function in dealing with box constraints and Lagrange multipliers in handling linear equality constraints, and attempts to obtain a solution of good quality by generating a minimum point of a barrier problem for a sequence of descending values of the barrier parameter. For any given value of the barrier parameter, the algorithm searches for a minimum point of the barrier problem in a feasible descent direction, which has a desired property that the box constraints are always satisfied automatically if the step length is a number between zero and one. At each iteration, the feasible descent direction is found by updating Lagrange multipliers with a globally convergent iterative procedure. For any given value of the barrier parameter, the algorithm converges to a stationary point of the barrier problem. Preliminary numerical results show that the algorithm seems effective and efficient. Copyright © 2012 Elsevier Ltd. All rights reserved.
The Galactic metallicity gradient
Rolleston, W. R. J.; Smartt, S. J.; Dufton, P. L.; Ryans, R. S. I.
2000-11-01
We have previously published intermediate to high resolution spectroscopic observations of approximately 80 early B-type main-sequence stars situated in 19 Galactic open clusters/associations with Galactocentric distances distributed over 6Twarog et al. \\cite{twa97}). However, there is no evidence to suggest that our data would be better fitted with a two-zone model. Moreover, we observe a N/O gradient of -0.04+/-0.02 dex kpc-1 which is consistent with that found for other spiral galaxies (Vila-Costas & Edmunds \\cite{vil93}).
[Translaminar Gradient and Glaucoma].
Čmelo, J
2017-01-01
The cribriform plate is a threshold of the intraocular pressure (VOT) and of the intracranial pressure (IKT). The difference between the VOT and IKT is referred to as translaminar gradient (TLG). The goal was to evaluate the Glaucoma progression (visual field, fundus examination, HRT) with / without topical anti-glaucomatous therapy) in relation to the TLG. the significance of TLG has been studied in two groups. I. Group: 57 patients diagnosed and treatment of Primary Open-Angle Glaucoma (PGOU), 10 patients with Ocular hypertension (OH), 7 patients with Normal-Tension Glaucoma (NTG), and 75 healthy without glaucoma. The examinations of TLG were carried out once and retrospectively. In II. group there were prospectively studied 14 patients with OH and 24 patients with newly detected PGOU without local therapy. The examinations were performed 4 times at intervals of 10 to 11 months. All tests included a basic eye examination, ORA tonometry, HRT examination, gonioscopy, Color Doppler sonography of blood vessels of the eye and orbit. Venous pulsation pressure (VPT) has been recorded by the Ophthalmodynamometer Meditron (D-ODM). In case of spontaneous retinal venous pulsation, VPT was considered as the same pressure as the VOT. The TLG was calculated with formula of Querfurth: ICT = 0.29 + 0.74 (VOT / PI (AO)). [PI(AO) - Pulsatility index of the Ophthalmic artery (AO)]. I. group: TLG was in the control group without Glaucoma: 12.2 ± 2.0 torr. The NTG group: 9.0 ± 1.70 mm Hg. PGOU: 11.1 ± 1.91 mm Hg. OH: 12.6 ± 0.85 mm Hg. IKT alone does not show a significant relationship to the presence of glaucoma, ocular hypertension. II. Group: The average TLG in Ocular Hypertension (14 patients) has been 3.8 ± 1.2 torr. 2 patients (OH) had TLG 10 torr. and 15 torr. After 4 years in one of them (TLG = 15 torr.) there was recorded Glaucoma progression. In the PGOU group before antiglaucoma therapy, TLG was 15.0 ± 4.8 torr for all patients. After setting up local anti
An alternative treatment of phenomenological higher-order strain-gradient plasticity theory
DEFF Research Database (Denmark)
Kuroda, Mitsutoshi; Tvergaard, Viggo
2010-01-01
strain is discussed, applying a dislocation theory-based consideration. Then, a differential equation for the equivalent plastic strain-gradient is introduced as an additional governing equation. Its weak form makes it possible to deduce and impose extra boundary conditions for the equivalent plastic...... strain. A connection between the present treatment and strain-gradient theories based on an extended virtual work principle is discussed. Furthermore, a numerical implementation and analysis of constrained simple shear of a thin strip are presented....
A spectral KRMI conjugate gradient method under the strong-Wolfe line search
Khadijah, Wan; Rivaie, Mohd.; Mamat, Mustafa; Jusoh, Ibrahim
2016-06-01
In this paper, a modification of spectral conjugate gradient (CG) method is proposed which combines the advantages of the spectral CG method and the RMIL method namely as spectral Khadijah-Rivaie-Mustafa-Ibrahim (SKRMI) to solve unconstrained optimization problems. Based on inexact line searches, the objective function generates a sufficient descent direction and the global convergence property for the proposed method has been proved. Moreover, the method reduces to the standard RMIL method if exact line search is applied. Numerical results are also presented to examine the efficiency of the proposed method.
A two-stage fuzzy chance-constrained water management model.
Xu, Jiaxuan; Huang, Guohe; Li, Zoe; Chen, Jiapei
2017-05-01
In this study, an inexact two-stage fuzzy gradient chance-constrained programming (ITSFGP) method is developed and applied to the water resources management in the Heshui River Basin, Jiangxi Province, China. The optimization model is established by incorporating interval programming, two-stage stochastic programming, and fuzzy gradient chance-constrained programming within an optimization framework. The hybrid model can address uncertainties represented as fuzzy sets, probability distributions, and interval numbers. It can effectively tackle the interactions between pre-regulated economic targets and the associated environmental penalties attributed to water allocation schemes and reflect the tradeoffs between economic revenues and system-failure risk. Furthermore, uncertainties associated with the decision makers' preferences are considered in decision-making processes. The obtained results can provide decision support for the local sustainable economic development and water resources allocation strategies under multiple uncertainties.
Generalized conjugate gradient squared
Energy Technology Data Exchange (ETDEWEB)
Fokkema, D.R.; Sleijpen, G.L.G. [Utrecht Univ. (Netherlands)
1994-12-31
In order to solve non-symmetric linear systems of equations, the Conjugate Gradient Squared (CGS) is a well-known and widely used iterative method. In practice the method converges fast, often twice as fast as the Bi-Conjugate Gradient method. This is what you may expect, since CGS uses the square of the BiCG polynomial. However, CGS may suffer from its erratic convergence behavior. The method may diverge or the approximate solution may be inaccurate. BiCGSTAB uses the BiCG polynomial and a product of linear factors in an attempt to smoothen the convergence. In many cases, this has proven to be very effective. Unfortunately, the convergence of BiCGSTAB may stall when a linear factor (nearly) degenerates. BiCGstab({ell}) is designed to overcome this degeneration of linear factors. It generalizes BiCGSTAB and uses both the BiCG polynomial and a product of higher order factors. Still, CGS may converge faster than BiCGSTAB or BiCGstab({ell}). So instead of using a product of linear or higher order factors, it may be worthwhile to look for other polynomials. Since the BiCG polynomial is based on a three term recursion, a natural choice would be a polynomial based on another three term recursion. Possibly, a suitable choice of recursion coefficients would result in method that converges faster or as fast as CGS, but less erratic. It turns out that an algorithm for such a method can easily be formulated. One particular choice for the recursion coefficients leads to CGS. Therefore one could call this algorithm generalized CGS. Another choice for the recursion coefficients leads to BiCGSTAB. It is therefore possible to mix linear factors and some polynomial based on a three term recursion. This way one may get the best of both worlds. The authors will report on their findings.
Library Support for Resource Constrained Accelerators
DEFF Research Database (Denmark)
Brock-Nannestad, Laust; Karlsson, Sven
2014-01-01
Accelerators, and other resource constrained systems, are increasingly being used in computer systems. Accelerators provide power efficient performance and often provide a shared memory model. However, it is a challenge to map feature rich APIs, such as OpenMP, to resource constrained systems...
How our biology constrains our science
Vlerick, Michael
2017-01-01
Reasoning from a naturalistic perspective, viewing the mind as an evolved biological organ with a particular structure and function, a number of influential philosophers and cognitive scientists claim that science is constrained by human nature. How exactly our genetic constitution constrains
Bayesian evaluation of inequality constrained hypotheses
Gu, X.; Mulder, J.; Deković, M.; Hoijtink, H.
2014-01-01
Bayesian evaluation of inequality constrained hypotheses enables researchers to investigate their expectations with respect to the structure among model parameters. This article proposes an approximate Bayes procedure that can be used for the selection of the best of a set of inequality constrained
Chance-Constrained Guidance With Non-Convex Constraints
Ono, Masahiro
2011-01-01
Missions to small bodies, such as comets or asteroids, require autonomous guidance for descent to these small bodies. Such guidance is made challenging by uncertainty in the position and velocity of the spacecraft, as well as the uncertainty in the gravitational field around the small body. In addition, the requirement to avoid collision with the asteroid represents a non-convex constraint that means finding the optimal guidance trajectory, in general, is intractable. In this innovation, a new approach is proposed for chance-constrained optimal guidance with non-convex constraints. Chance-constrained guidance takes into account uncertainty so that the probability of collision is below a specified threshold. In this approach, a new bounding method has been developed to obtain a set of decomposed chance constraints that is a sufficient condition of the original chance constraint. The decomposition of the chance constraint enables its efficient evaluation, as well as the application of the branch and bound method. Branch and bound enables non-convex problems to be solved efficiently to global optimality. Considering the problem of finite-horizon robust optimal control of dynamic systems under Gaussian-distributed stochastic uncertainty, with state and control constraints, a discrete-time, continuous-state linear dynamics model is assumed. Gaussian-distributed stochastic uncertainty is a more natural model for exogenous disturbances such as wind gusts and turbulence than the previously studied set-bounded models. However, with stochastic uncertainty, it is often impossible to guarantee that state constraints are satisfied, because there is typically a non-zero probability of having a disturbance that is large enough to push the state out of the feasible region. An effective framework to address robustness with stochastic uncertainty is optimization with chance constraints. These require that the probability of violating the state constraints (i.e., the probability of
A Constrained Algorithm Based NMFα for Image Representation
Directory of Open Access Journals (Sweden)
Chenxue Yang
2014-01-01
Full Text Available Nonnegative matrix factorization (NMF is a useful tool in learning a basic representation of image data. However, its performance and applicability in real scenarios are limited because of the lack of image information. In this paper, we propose a constrained matrix decomposition algorithm for image representation which contains parameters associated with the characteristics of image data sets. Particularly, we impose label information as additional hard constraints to the α-divergence-NMF unsupervised learning algorithm. The resulted algorithm is derived by using Karush-Kuhn-Tucker (KKT conditions as well as the projected gradient and its monotonic local convergence is proved by using auxiliary functions. In addition, we provide a method to select the parameters to our semisupervised matrix decomposition algorithm in the experiment. Compared with the state-of-the-art approaches, our method with the parameters has the best classification accuracy on three image data sets.
Block-triangular preconditioners for PDE-constrained optimization
Rees, Tyrone
2010-11-26
In this paper we investigate the possibility of using a block-triangular preconditioner for saddle point problems arising in PDE-constrained optimization. In particular, we focus on a conjugate gradient-type method introduced by Bramble and Pasciak that uses self-adjointness of the preconditioned system in a non-standard inner product. We show when the Chebyshev semi-iteration is used as a preconditioner for the relevant matrix blocks involving the finite element mass matrix that the main drawback of the Bramble-Pasciak method-the appropriate scaling of the preconditioners-is easily overcome. We present an eigenvalue analysis for the block-triangular preconditioners that gives convergence bounds in the non-standard inner product and illustrates their competitiveness on a number of computed examples. Copyright © 2010 John Wiley & Sons, Ltd.
Basic Strain Gradient Plasticity Theories with Application to Constrained Film Deformation
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Hutchinson, John W.
2011-01-01
films: the compression or extension of a finite layer joining rigid platens. Full elastic-plastic solutions are obtained for the same problem based on a finite element method devised for the new class of flow theories. Potential difficulties and open issues associated with the new class of flow theories...
Order-constrained linear optimization.
Tidwell, Joe W; Dougherty, Michael R; Chrabaszcz, Jeffrey S; Thomas, Rick P
2017-11-01
Despite the fact that data and theories in the social, behavioural, and health sciences are often represented on an ordinal scale, there has been relatively little emphasis on modelling ordinal properties. The most common analytic framework used in psychological science is the general linear model, whose variants include ANOVA, MANOVA, and ordinary linear regression. While these methods are designed to provide the best fit to the metric properties of the data, they are not designed to maximally model ordinal properties. In this paper, we develop an order-constrained linear least-squares (OCLO) optimization algorithm that maximizes the linear least-squares fit to the data conditional on maximizing the ordinal fit based on Kendall's τ. The algorithm builds on the maximum rank correlation estimator (Han, 1987, Journal of Econometrics, 35, 303) and the general monotone model (Dougherty & Thomas, 2012, Psychological Review, 119, 321). Analyses of simulated data indicate that when modelling data that adhere to the assumptions of ordinary least squares, OCLO shows minimal bias, little increase in variance, and almost no loss in out-of-sample predictive accuracy. In contrast, under conditions in which data include a small number of extreme scores (fat-tailed distributions), OCLO shows less bias and variance, and substantially better out-of-sample predictive accuracy, even when the outliers are removed. We show that the advantages of OCLO over ordinary least squares in predicting new observations hold across a variety of scenarios in which researchers must decide to retain or eliminate extreme scores when fitting data. © 2017 The British Psychological Society.
Gradient Boosting Machines, A Tutorial
Directory of Open Access Journals (Sweden)
Alexey eNatekin
2013-12-01
Full Text Available Gradient boosting machines are a family of powerful machine-learning techniques that have shown considerable success in a wide range of practical applications. They are highly customizable to the particular needs of the application, like being learned with respect to different loss functions. This article gives a tutorial introduction into the methodology of gradient boosting methods. A theoretical information is complemented with many descriptive examples and illustrations which cover all the stages of the gradient boosting model design. Considerations on handling the model complexity are discussed. A set of practical examples of gradient boosting applications are presented and comprehensively analyzed.
Caste-, work-, and descent-based discrimination as a determinant of health in social epidemiology.
Patil, Rajan R
2014-01-01
Social epidemiology explores health in the context of broad social determinants of health, where the boundary lines between health and politics appear increasingly blurred. Social determinants of health such as caste, discrimination, and social exclusion are inherently political in nature, hence it becomes imperative to look at health through a broader perspective of political philosophy, ideology, and caste that imposes enormous obstacles to a person's full attainment of civil, political, economic, social, and cultural rights. Caste is descent based and hereditary in nature. It is a characteristic determined by one's birth into a particular caste, irrespective of the faith practiced by the individual. Caste denotes a system of rigid social stratification into ranked groups defined by descent and occupation. Under various caste systems throughout the world, caste divisions also dominate in housing, marriage, and general social interaction divisions that are reinforced through the practice and threat of social ostracism, economic boycotts, and even physical violence-all of which undermine health equality.
Dwyer Cianciolo, Alicia M. (Editor)
2011-01-01
NASA senior management commissioned the Entry, Descent and Landing Systems Analysis (EDL-SA) Study in 2008 to identify and roadmap the Entry, Descent and Landing (EDL) technology investments that the agency needed to successfully land large payloads at Mars for both robotic and human-scale missions. Year 1 of the study focused on technologies required for Exploration-class missions to land payloads of 10 to 50 mt. Inflatable decelerators, rigid aeroshell and supersonic retro-propulsion emerged as the top candidate technologies. In Year 2 of the study, low TRL technologies identified in Year 1, inflatables aeroshells and supersonic retropropulsion, were combined to create a demonstration precursor robotic mission. This part of the EDL-SA Year 2 effort, called Exploration Feed Forward (EFF), took much of the systems analysis simulation and component model development from Year 1 to the next level of detail.
Identity-by-descent mapping in a Scandinavian multiple sclerosis cohort
DEFF Research Database (Denmark)
Westerlind, Helga; Imrell, Kerstin; Ramanujam, Ryan
2015-01-01
In an attempt to map chromosomal regions carrying rare gene variants contributing to the risk of multiple sclerosis (MS), we identified segments shared identical-by-descent (IBD) using the software BEAGLE 4.0's refined IBD analysis. IBD mapping aims at identifying segments inherited from a common....... This marker was located within the GNA11 gene, which contains no previous association with MS. We conclude that IBD mapping is not sufficiently powered to identify MS risk loci even in ethnically relatively homogenous populations, or that alternatively rare variants are not adequately present....... a total of 441 731 markers for the analysis. After identification of segments shared by descent and significance testing, a filter function for markers with low IBD sharing was applied. Four regions on chromosomes 5, 9, 14 and 19 were found to be significantly associated with the risk for MS. However, all...
Reactions to secondhand smoke by nonsmokers of Korean descent: clash of cultures?
Hughes, Suzanne C; Usita, Paula M; Hovell, Melbourne F; Richard Hofstetter, C
2011-08-01
Koreans hail from a culture where men's smoking and secondhand smoke (SHS) exposure were the norm. Little is known about how nonsmokers of Korean descent respond to smokers in the United States. In 2007-2008, trained moderators conducted eight focus groups with nonsmokers (n = 47) of Korean descent in San Diego. Participants discussed their personal experiences and views concerning SHS. Most participants detected SHS quickly and disliked the smell. Their reactions differed by gender, age, and how well they knew the smoker. Reactions ranged from passive (e.g., tolerating SHS or staring) to assertive (moving or asking the smoker to stop smoking). Younger participants were more tolerant than older participants. Participants appeared caught between two cultures. Despite high awareness, they struggled with how to avoid SHS in a manner befitting of their social status and Korean values. Culturally sensitive programs are needed for immigrants such as Koreans in the United States.
A stochastic constrained optimization technique and its application to detector array processing.
Winkler, L. P.; Schwartz, M.
1971-01-01
A stochastic projected gradient algorithm is proposed which can be used for finding a constrained optimum point for a concave or convex objective function subject to nonlinear constraints which form a connected region even when only a noisy estimate of the objective function is available. For a constraint described by a single linear equation, convergence to the constrained optimum value is proved, and the rate of convergence of the algorithm to the constrained optimum value is determined. The algorithm is applied to the nonlinear problem of obtaining automatically an array of detectors which forms a beam in a desired direction in space in the presence of interfering noise so as to maximize the SNR subject to a constraint on the super-gain ratio.
Matsuyama, Y
1998-01-01
Multiple descent cost competition is a composition of learning phases for minimizing a given measure of total performance, i.e., cost. If these phases are heterogeneous toward each other, the total learning algorithm shows a variety of extraordinary abilities; especially in regards to multimedia information processing. In the first phase of descent cost learning, elements of source data are grouped. Simultaneously, a weight vector for minimal learning, (i.e., a winner), is found. Then, the winner and its partners are updated for further cost reduction. Therefore, two classes of self-organizing feature maps are generated. One is called a grouping feature map, which partitions the source data. The other is an ordinary weight vector feature map. The grouping feature map, together with the winners, retains most of the source data information. This feature map is able to assist in a high quality approximation of the original data. Traditional weight vector feature maps lack this ability. Another important capacity of the grouping feature map is that it can change its shape. Thus, the grouping pattern can accept external directions in order to metamorphose. In the text, the total algorithm of the multiple descent cost competition is explained first. In that section, image processing concepts are introduced in order to assist in the description of this algorithm. Then, a still image is first data-compressed (DC). Next, a restored image is morphed using the grouping feature map by receiving directions given by an external intelligence. Next, an interpolation of frames is applied in order to complete animation coding (AC). Thus, multiple descent cost competition bridges "DC to AC." Examples of multimedia processing on virtual digital movies are given.
Scaling Up Coordinate Descent Algorithms for Large ℓ1 Regularization Problems
Energy Technology Data Exchange (ETDEWEB)
Scherrer, Chad; Halappanavar, Mahantesh; Tewari, Ambuj; Haglin, David J.
2012-07-03
We present a generic framework for parallel coordinate descent (CD) algorithms that has as special cases the original sequential algorithms of Cyclic CD and Stochastic CD, as well as the recent parallel Shotgun algorithm of Bradley et al. We introduce two novel parallel algorithms that are also special cases---Thread-Greedy CD and Coloring-Based CD---and give performance measurements for an OpenMP implementation of these.
The relief formed by the descent phenomenon in the north-east part of Kosova.
Bulliqi, Shpejtim; Isufi, Florim; Ramadani, Ibrahim; Gashi, Gani
2012-04-01
In the diverse relief of north-east part of Kosova a relatively wide range occupies the relief modelled by the descent phenomenon, which is conditioned by morph-structural and climatic factors quite suitable for their development. The morphogenesis activity of descent phenomenon is conditioned by the types of rocks, tectonic process of this region and climatic conditions. These factors condition horizontal and vertical relief fragmentation, slope, especially in Gollaku mountains and in SE part of Kopaonik mountain. Along the tectonic descents, the steepness is detaching and the detaching lines consisting of magmatic rocks show overthrows, demolitions and stony torrents, but the Teri gene composition formations are modelled by sliding and muddy torrents, depending upon the presence of clayey and alevrolite belts on these Teri gene ones. The impact of factors and conditions on the relief of this part, the phenomena like demolitions, overthrows, sliding, muddy torrents, stony torrents, etc, operate here, which play an important morphological role in the modelling of relief.
Controlled weather balloon ascents and descents for atmospheric research and climate monitoring
Kräuchi, Andreas; Philipona, Rolf; Romanens, Gonzague; Hurst, Dale F.; Hall, Emrys G.; Jordan, Allen F.
2016-03-01
In situ upper-air measurements are often made with instruments attached to weather balloons launched at the surface and lifted into the stratosphere. Present-day balloon-borne sensors allow near-continuous measurements from the Earth's surface to about 35 km (3-5 hPa), where the balloons burst and their instrument payloads descend with parachutes. It has been demonstrated that ascending weather balloons can perturb the air measured by very sensitive humidity and temperature sensors trailing behind them, particularly in the upper troposphere and lower stratosphere (UTLS). The use of controlled balloon descent for such measurements has therefore been investigated and is described here. We distinguish between the single balloon technique that uses a simple automatic valve system to release helium from the balloon at a preset ambient pressure, and the double balloon technique that uses a carrier balloon to lift the payload and a parachute balloon to control the descent of instruments after the carrier balloon is released at preset altitude. The automatic valve technique has been used for several decades for water vapor soundings with frost point hygrometers, whereas the double balloon technique has recently been re-established and deployed to measure radiation and temperature profiles through the atmosphere. Double balloon soundings also strongly reduce pendulum motion of the payload, stabilizing radiation instruments during ascent. We present the flight characteristics of these two ballooning techniques and compare the quality of temperature and humidity measurements made during ascent and descent.
Levator co-activation is a significant confounder of pelvic organ descent on Valsalva maneuver.
Ornö, A K; Dietz, H P
2007-09-01
A Valsalva maneuver is used clinically and on imaging in order to determine female pelvic organ prolapse. We have examined the potential confounding effect of levator co-activation at the time of a Valsalva maneuver and the impact of repetition with biofeedback instruction. Fifty nulliparous women at 36-38 weeks' gestation received 3D/4D translabial ultrasound investigation in the dorsal resting position after bladder emptying. Valsalva maneuvers were recorded initially and after repeated attempts with visual biofeedback both during the maneuver and after, with the operator demonstrating findings on the ultrasound monitor, in order to abolish levator co-activation. Offline analysis was subsequently undertaken. Significant differences between first and optimal Valsalva maneuver were found for bladder neck position, bladder neck descent, hiatal sagittal diameter and hiatal area on Valsalva. In a minority of women (22/50) we observed a reduction in the sagittal hiatal diameter on first Valsalva maneuver, indicating levator co-activation. A reduction in sagittal diameter was seen in only 11/50 after instruction. Levator co-activation was associated with significantly lower bladder neck descent. The Valsalva maneuver is frequently accompanied by a pelvic floor muscle contraction. Levator co-activation may be a substantial confounder, reducing pelvic organ descent. Without repetition and digital, auditory or visual biofeedback, women may not perform a correct Valsalva maneuver. Biofeedback markedly reduces the likelihood of levator co-activation but does not abolish it completely. Copyright 2007 ISUOG. Published by John Wiley & Sons, Ltd.
Denaturing gradient gel electrophoresis
International Nuclear Information System (INIS)
Kocherginskaya, S.A.; Cann, I.K.O.; Mackie, R.I.
2005-01-01
It is worthwhile considering that only some 30 species make up the bulk of the bacterial population in human faeces at any one time based on the classical cultivation-based approach. The situation in the rumen is similar. Thus, it is practical to focus on specific groups of interest within the complex community. These may be the predominant or the most active species, specific physiological groups or readily identifiable (genetic) clusters of phylogenetically related organisms. Several 16S rDNA fingerprinting techniques can be invaluable for selecting and monitoring sequences or phylogenetic groups of interest and are described below. Over the past few decades, considerable attention was focussed on the identification of pure cultures of microbes on the basis of genetic polymorphisms of DNA encoding rRNA such as ribotyping, amplified fragment length polymorphism and randomly amplified polymorphic DNA. However, many of these methods require prior cultivation and are less suitable for use in analysis of complex mixed populations although important in describing cultivated microbial diversity in molecular terms. Much less attention was given to molecular characterization of complex communities. In particular, research into diversity and community structure over time has been revolutionized by the advent of molecular fingerprinting techniques for complex communities. Denaturing or temperature gradient gel electrophoresis (DGGE/TGGE) methods have been successfully applied to the analysis of human, pig, cattle, dog and rodent intestinal populations
O'Connor, Michelle Y; Thoreson, Caroline K; Ramsey, Natalie L M; Ricks, Madia; Sumner, Anne E
2013-01-01
Vitamin D levels in people of African descent are often described as inadequate or deficient. Whether low vitamin D levels in people of African descent lead to compromised bone or cardiometabolic health is unknown. Clarity on this issue is essential because if clinically significant vitamin D deficiency is present, vitamin D supplementation is necessary. However, if vitamin D is metabolically sufficient, vitamin D supplementation could be wasteful of scarce resources and even harmful. In this review vitamin D physiology is described with a focus on issues specific to populations of African descent such as the influence of melanin on endogenous vitamin D production and lactose intolerance on the willingness of people to ingest vitamin D fortified foods. Then data on the relationship of vitamin D to bone and cardiometabolic health in people of African descent are evaluated. © 2013.
Meinema, Jennita G.; van Dijk, Nynke; Beune, Erik J. A. J.; Jaarsma, Debbie A. D. C.; van Weert, Henk C. P. M.; Haafkens, Joke A.
2015-01-01
Background In Western countries, better knowledge about patient-related determinants of treatment adherence (medication and lifestyle) is needed to improve treatment adherence and outcomes among hypertensive ethnic minority patients of African descent. Objective To identify patient-related
International Nuclear Information System (INIS)
Vilar, L.C.Q.; Sasaki, C.A.G.; Sorella, S.P.
1996-09-01
The supersymmetric descent equations in superspace are discussed by means of the introduction of two operators ζ α , ζ -α which allow to decompose the supersymmetric covariant derivatives D α , D -α as BRS commutators. (author). 27 refs., 4 tabs
Gradient vs. approximation design optimization techniques in low-dimensional convex problems
Fedorik, Filip
2013-10-01
Design Optimization methods' application in structural designing represents a suitable manner for efficient designs of practical problems. The optimization techniques' implementation into multi-physical softwares permits designers to utilize them in a wide range of engineering problems. These methods are usually based on modified mathematical programming techniques and/or their combinations to improve universality and robustness for various human and technical problems. The presented paper deals with the analysis of optimization methods and tools within the frame of one to three-dimensional strictly convex optimization problems, which represent a component of the Design Optimization module in the Ansys program. The First Order method, based on combination of steepest descent and conjugate gradient method, and Supbproblem Approximation method, which uses approximation of dependent variables' functions, accompanying with facilitation of Random, Sweep, Factorial and Gradient Tools, are analyzed, where in different characteristics of the methods are observed.
Characterization of gradient control systems
Cortés, Jorge; van der Schaft, Arjan; Crouch, Peter E.
2005-01-01
Given a general nonlinear affine control system with outputs and a torsion-free affine connection defined on its state space, we investigate the gradient realization problem: we give necessary and sufficient conditions under which the control system can be written as a gradient control system
A Dynamic Programming Approach to Constrained Portfolios
DEFF Research Database (Denmark)
Kraft, Holger; Steffensen, Mogens
2013-01-01
This paper studies constrained portfolio problems that may involve constraints on the probability or the expected size of a shortfall of wealth or consumption. Our first contribution is that we solve the problems by dynamic programming, which is in contrast to the existing literature that applies...... the martingale method. More precisely, we construct the non-separable value function by formalizing the optimal constrained terminal wealth to be a (conjectured) contingent claim on the optimal non-constrained terminal wealth. This is relevant by itself, but also opens up the opportunity to derive new solutions...
Kalman, Lisa; Wilson, Jean Amos; Buller, Arlene; Dixon, John; Edelmann, Lisa; Geller, Louis; Highsmith, William Edward; Holtegaard, Leonard; Kornreich, Ruth; Rohlfs, Elizabeth M.; Payeur, Toby L.; Sellers, Tina; Toji, Lorraine; Muralidharan, Kasinathan
2009-01-01
Many recessive genetic disorders are found at a higher incidence in people of Ashkenazi Jewish (AJ) descent than in the general population. The American College of Medical Genetics and the American College of Obstetricians and Gynecologists have recommended that individuals of AJ descent undergo carrier screening for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, and Gaucher disease. Although the...
The geomagnetic field gradient tensor
DEFF Research Database (Denmark)
Kotsiaros, Stavros; Olsen, Nils
2012-01-01
We develop the general mathematical basis for space magnetic gradiometry in spherical coordinates. The magnetic gradient tensor is a second rank tensor consisting of 3 × 3 = 9 spatial derivatives. Since the geomagnetic field vector B is always solenoidal (∇ · B = 0) there are only eight independent...... tensor elements. Furthermore, in current free regions the magnetic gradient tensor becomes symmetric, further reducing the number of independent elements to five. In that case B is a Laplacian potential field and the gradient tensor can be expressed in series of spherical harmonics. We present properties...... of the magnetic gradient tensor and provide explicit expressions of its elements in terms of spherical harmonics. Finally we discuss the benefit of using gradient measurements for exploring the Earth’s magnetic field from space, in particular the advantage of the various tensor elements for a better determination...
Gradient zone boundary control in salt gradient solar ponds
Energy Technology Data Exchange (ETDEWEB)
Hull, John R. (Downers Grove, IL)
1984-01-01
A method and apparatus for suppressing zone boundary migration in a salt gradient solar pond includes extending perforated membranes across the pond at the boundaries, between the convective and non-convective zones, the perforations being small enough in size to prevent individual turbulence disturbances from penetrating the hole, but being large enough to allow easy molecular diffusion of salt thereby preventing the formation of convective zones in the gradient layer. The total area of the perforations is a sizable fraction of the membrane area to allow sufficient salt diffusion while preventing turbulent entrainment into the gradient zone.
Compositionally Constraining Elysium Lava Fields
Karunatillake, S.; Button, N. E.; Skok, J. R.
2013-12-01
Chemical provinces of Mars defined recently [1-3] became possible with the maps of elemental mass fractions generated with Mars Odyssey Gamma and Neutron Spectrometer (GS) data [4,5]. These provide a unique perspective by representing compositional signatures distinctive of the regolith vertically at decimeter depths and laterally at hundreds of kilometer scale. Some provinces overlap compellingly with regions highlighted by other remote sensing observations, such as the Mars Radar Stealth area [3]. The spatial convergence of mutually independent data with the consequent highlight of a region provides a unique opportunity of insight not possible with a single type of remote sensing observation. Among such provinces, previous work [3] highlighted Elysium lava flows as a promising candidate on the basis of convergence with mapped geologic units identifying Elysium's lava fields generally, and Amazonian-aged lava flows specifically. The South Eastern lava flows of Elysium Mons, dating to the recent Amazonian epoch, overlap compellingly with a chemical province of K and Th depletion relative to the Martian midlatitudes. We characterize the composition, geology, and geomorphology of the SE Elysium province to constrain the confluence of geologic and alteration processes that may have contributed to its evolution. We compare this with the North Western lava fields, extending the discussion on chemical products from the thermal evolution of Martian volcanism as discussed by Baratoux et al. [6]. The chemical province, by regional proximity to Cerberus Fossae, may also reflect the influence of recently identified buried flood channels [7] in the vicinity of Orcus Patera. Despite the compelling chemical signature from γ spectra, fine grained unconsolidated sediment hampers regional VNTIR (Visible, Near, and Thermal Infrared) spectral analysis. But some observations near scarps and fresh craters allow a view of small scale mineral content. The judicious synthesis of
Constrained vertebrate evolution by pleiotropic genes
DEFF Research Database (Denmark)
Hu, Haiyang; Uesaka, Masahiro; Guo, Song
2017-01-01
Despite morphological diversification of chordates over 550 million years of evolution, their shared basic anatomical pattern (or 'bodyplan') remains conserved by unknown mechanisms. The developmental hourglass model attributes this to phylum-wide conserved, constrained organogenesis stages that ...
Asymptotic Likelihood Distribution for Correlated & Constrained Systems
Agarwal, Ujjwal
2016-01-01
It describes my work as summer student at CERN. The report discusses the asymptotic distribution of the likelihood ratio for total no. of parameters being h and 2 out of these being are constrained and correlated.
Optimization of gradient coil technology for human magnetic resonance imaging
Chronik, Blaine Alexander
The general problem of identifying the optimal gradient coil design for any given application is addressed in this thesis. The problem is divided into stages. The first step is the development of an optimal mathematical solution for single designs conforming to some set of constraints. The second step is the systematic implementation of the mathematical algorithm to search for the optimal set of design constraints for an intended application, two examples of which are investigated. The final step is the consideration of gradient coil dependent physiological limits specific to the application of strong gradient fields in human subjects. A modified minimum inductance target field method that allows the placement of a set of constraints on the final current density is developed. This constrained current minimum inductance (CCMI) method is derived in the context of previous target field methods. The method has been fully implemented on computer and applied to the design of both central and edge uniformity gradient coils. A three axis gradient coil set that utilizes interleaved, multilayer axes to achieve maximum gradient strengths of over 2000mT/m in rise times of less than 50μs with an inner coil diameter of 5cm was designed. Water cooling was incorporated into the coil to assist in thermal management. The duty cycle for the most extreme cases of single shot EPI is limited by the thermal response and expressions for maximum rates of image collection are given for burst and continuous modes of operation. A three axis gradient coil set with an imaging region extending outside the physical edge of the coil was designed, constructed, and tested. The configuration is compatible with both neck and brain imaging in humans. The coil produces a cylindrical imaging region 16cm in diameter and 16cm in length. The coil axes produce gradient strengths between 80mT/m and 100mT/m at 250A peak current, with minimum rise times of approximately 400μs. Heating tests were performed
A Variant of the Topkis-Veinott Method for Solving Inequality Constrained Optimization Problems
International Nuclear Information System (INIS)
Birge, J. R.; Qi, L.; Wei, Z.
2000-01-01
In this paper we give a variant of the Topkis-Veinott method for solving inequality constrained optimization problems. This method uses a linearly constrained positive semidefinite quadratic problem to generate a feasible descent direction at each iteration. Under mild assumptions, the algorithm is shown to be globally convergent in the sense that every accumulation point of the sequence generated by the algorithm is a Fritz-John point of the problem. We introduce a Fritz-John (FJ) function, an FJ1 strong second-order sufficiency condition (FJ1-SSOSC), and an FJ2 strong second-order sufficiency condition (FJ2-SSOSC), and then show, without any constraint qualification (CQ), that (i) if an FJ point z satisfies the FJ1-SSOSC, then there exists a neighborhood N(z) of z such that, for any FJ point y element of N(z) {z } , f 0 (y) ≠ f 0 (z) , where f 0 is the objective function of the problem; (ii) if an FJ point z satisfies the FJ2-SSOSC, then z is a strict local minimum of the problem. The result (i) implies that the entire iteration point sequence generated by the method converges to an FJ point. We also show that if the parameters are chosen large enough, a unit step length can be accepted by the proposed algorithm
Strain gradients in epitaxial ferroelectrics
International Nuclear Information System (INIS)
Catalan, G.; Noheda, B.; McAneney, J.; Sinnamon, L.J.; Gregg, J.M.
2005-01-01
X-ray analysis of ferroelectric thin layers of Ba 1/2 Sr 1/2 TiO 3 with different thicknesses reveals the presence of strain gradients across the films and allows us to propose a functional form for the internal strain profile. We use this to calculate the influence of strain gradient, through flexoelectric coupling, on the degradation of the ferroelectric properties of films with decreasing thickness, in excellent agreement with the observed behavior. This paper shows that strain relaxation can lead to smooth, continuous gradients across hundreds of nanometers, and it highlights the pressing need to avoid such strain gradients in order to obtain ferroelectric films with bulklike properties
Entry, Descent, and Landing Communications for the 2011 Mars Science Laboratory
Abilleira, Fernando; Shidner, Jeremy D.
2012-01-01
The Mars Science Laboratory (MSL), established as the most advanced rover to land on the surface of Mars to date, launched on November 26th, 2011 and arrived to the Martian Gale Crater during the night of August 5th, 2012 (PDT). MSL will investigate whether the landing region was ever suitable to support carbon-based life, and examine rocks, soil, and the atmosphere with a sophisticated suite of tools. This paper addresses the flight system requirement by which the vehicle transmitted indications of the following events using both X-band tones and UHF telemetry to allow identification of probable root causes should a mission anomaly have occurred: Heat-Rejection System (HRS) venting, completion of the cruise stage separation, turn to entry attitude, atmospheric deceleration, bank angle reversal commanded, parachute deployment, heatshield separation, radar ground acquisition, powered descent initiation, rover separation from the descent stage, and rover release. During Entry, Descent, and Landing (EDL), the flight system transmitted a UHF telemetry stream adequate to determine the state of the spacecraft (including the presence of faults) at 8 kbps initiating from cruise stage separation through at least one minute after positive indication of rover release on the surface of Mars. The flight system also transmitted X-band semaphore tones from Entry to Landing plus one minute although since MSL was occulted, as predicted, by Mars as seen from the Earth, Direct-To-Earth (DTE) communications were interrupted at approximately is approx. 5 min after Entry ( approximately 130 prior to Landing). The primary data return paths were through the Deep Space Network (DSN) for DTE and the existing Mars network of orbiting assets for UHF, which included the Mars Reconnaissance Orbiter (MRO), Mars Odyssey (ODY), and Mars Express (MEX) elements. These orbiters recorded the telemetry data stream and returned it back to Earth via the DSN. The paper also discusses the total power
Rosas, Lisa G; Harley, Kim; Fernald, Lia C H; Guendelman, Sylvia; Mejia, Fabiola; Neufeld, Lynnette M; Eskenazi, Brenda
2009-12-01
Children of Mexican descent frequently experience household food insecurity both in the United States and Mexico. However, little is known about the associations of food insecurity with dietary intake. This study aimed to understand the level of perceived food insecurity and its association with dietary intake among children of Mexican descent residing in the United States and Mexico. This cross-sectional study utilized data from a 2006 binational study of 5-year-old children of Mexican descent living in migrant communities in California and Mexico. In California, children were 301 participants from the Center for the Health Assessment of Mothers and Children of Salinas study, a longitudinal birth cohort in a Mexican immigrant community. Mexican children (n=301) were participants in the Proyecto Mariposa study, which was designed to capture a sample of women and their children living in Mexico who closely resembled the California sample, yet who never migrated to the United States. Household food insecurity was measured using the US Department of Agriculture Food Security Scale and dietary intake was assessed with food frequency questionnaires. Analysis of variance was used to examine unadjusted and adjusted differences in total energy, nutrient intake, and consumption of food groups by household food security status. Approximately 39% of California mothers and 75% of Mexico mothers reported low or very low food security in the past 12 months (P<0.01). Children in the United States experiencing food insecurity consumed more fat, saturated fat, sweets, and fried snacks than children not experiencing food insecurity. In contrast, in Mexico food insecurity was associated with lower intake of total carbohydrates, dairy, and vitamin B-6. Programs and policies addressing food insecurity in the United States and Mexico may need to take steps to address dietary intake among children in households experiencing food insecurity, possibly through education and programs to
Implementing the Mars Science Laboratory Terminal Descent Sensor Field Test Campaign
Montgomery, James F.; Bodie, James H.; Brown, Joseph D.; Chen, Allen; Chen, Curtis W.; Essmiller, John C.; Fisher, Charles D.; Goldberg, Hannah R.; Lee, Steven W.; Shaffer, Scott J.
2012-01-01
The Mars Science Laboratory (MSL) will deliver a 900 kg rover to the surface of Mars in August 2012. MSL will utilize a new pulse-Doppler landing radar, the Terminal Descent Sensor (TDS). The TDS employs six narrow-beam antennas to provide unprecedented slant range and velocity performance at Mars to enable soft touchdown of the MSL rover using a unique sky crane Entry, De-scent, and Landing (EDL) technique. Prior to use on MSL, the TDS was put through a rigorous verification and validation (V&V) process. A key element of this V&V was operating the TDS over a series of field tests, using flight-like profiles expected during the descent and landing of MSL over Mars-like terrain on Earth. Limits of TDS performance were characterized with additional testing meant to stress operational modes outside of the expected EDL flight profiles. The flight envelope over which the TDS must operate on Mars encompasses such a large range of altitudes and velocities that a variety of venues were neces-sary to cover the test space. These venues included an F/A-18 high performance aircraft, a Eurocopter AS350 AStar helicopter and 100-meter tall Echo Towers at the China Lake Naval Air Warfare Center. Testing was carried out over a five year period from July 2006 to June 2011. TDS performance was shown, in gen-eral, to be excellent over all venues. This paper describes the planning, design, and implementation of the field test campaign plus results and lessons learned.
A Cockpit Comfort Level of the Descent Capsule-Shaped Vehicles
Directory of Open Access Journals (Sweden)
V. E. Minenko
2017-01-01
Full Text Available The article formulates the task of selecting a design-layout pattern for a transport spacecraft, in terms of reaching a proper comfort level for the crew to have appropriate functioning. Using the example of a domestic spacecraft and an American one, it has been shown that the type of launch vehicle, the launch specifics, the operational overloads, and the overall mass restrictions have a dramatic impact on the choice of the design-layout pattern of the spacecraft. The free volume of the pressure cockpit per each member of the crew is considered as the main characteristic to show a level of the spacecraft comfort. Using the average statistical data on the layout density of different equipment, the article estimates the possible increase of this characteristic for the cutting-edge descent vehicles. Using the example of the descent vehicles of Soyuz and Apollo class, the article shows a dependence of the raising weight of a descent vehicle on the free volume of its pressure cockpit. Attention is drawn to the fact that the limit of increasing free space of the spacecraft compartments to achieve maximum comfort should correspond to a set of functions that the crew performs in the compartments considered. Otherwise, the increase in the spacecraft mass will prove to be unjustified. The results stated in the article can be useful to developers of manned spacecraft, as well as to teachers and students. In the long term it is worthwhile adding the article material with the mass and volume indicators, as well as with the estimate results of the comfort level of modern manned spacecrafts being under design in Russia and USA, such as PTK NP (“Federation”, “Orion”, “Dragon V2”.
Alcock, Lisa; O'Brien, Thomas D; Vanicek, Natalie
2015-12-16
Stair descent is an inherently complex form of locomotion posing a high falls risk for older adults, specifically when negotiating the transitional gait cycles linking level gait and descent. The aim of this study was to enhance our understanding of the biomechanical demands by comparing the demands of these transitions. Lower limb kinematics and kinetics of the 2-step transitions linking level and descent gait at the top (level-to-descent) and the bottom (descent-to-level) of the staircase were quantified in 36 older women with no falls history. Despite undergoing the same vertical displacement (2-steps), the following significant (pvelocity; reduced hip extension and increased ankle dorsiflexion (late stance/pre-swing); reduced ground reaction forces, larger knee extensor moments and powers (absorption; late stance); reduced ankle plantarflexor moments (early and late stance) and increased ankle powers (mid-stance). Top transition biomechanics were similar to those reported previously for continuous descent. Kinetic differences at the knee and ankle signify the contrasting and prominent functions of controlled lowering during the top transition and forward continuance during the bottom transition. The varying musculoskeletal demands encountered during each functional sub-task should be addressed in falls prevention programmes with elderly populations where the greatest clinical impact may be achieved. Knee extensor eccentric power through flexion exercises would facilitate a smooth transition at the top and improving ankle plantarflexion strength during single and double limb stance activities would ease the transition into level gait following continuous descent. Copyright © 2015 Elsevier Ltd. All rights reserved.
Gradient Index Optics at DARPA
2013-11-01
sodium, is submerged into a bath of molten salt containing a different ion, such as lithium bromide. Ions from the salt bath diffuse into the glass...molecules, creating a gradient of index of refraction (Mohr et al. 1979). • Crystal growing. From a silver- chloride /sodium- chloride bath, starting with a...sodium chloride seed, a crystal is pulled that begins to deplete the sodium in the bath and starts to pull silver, forming a gradient (Houde-Walter
Stochastic Gradient Monomial Gamma Sampler
Zhang, Yizhe; Chen, Changyou; Gan, Zhe; Henao, Ricardo; Carin, Lawrence
2017-01-01
Recent advances in stochastic gradient techniques have made it possible to estimate posterior distributions from large datasets via Markov Chain Monte Carlo (MCMC). However, when the target posterior is multimodal, mixing performance is often poor. This results in inadequate exploration of the posterior distribution. A framework is proposed to improve the sampling efficiency of stochastic gradient MCMC, based on Hamiltonian Monte Carlo. A generalized kinetic function is leveraged, delivering ...
What is Ubuntu? Different Interpretations among South Africans of African Descent
DEFF Research Database (Denmark)
Gade, Christian B.N.
2012-01-01
In this article, I describe and systematize the different answers to the question 'What is Ubuntu?' that I have been able to identify among South Africans of African descent (SAADs). I show that it is possible to distinguish between two clusters of answers. The answers of the first cluster all...... define ubuntu as a moral quality of a person, while the answers of the second cluster all define ubuntu as a phenomenon (for instance a philosophy, an ethic, African humanism, or, a wordview) according to which persons are interconnected. The concept of a person is of central importance to all...
The Mars Exploration Rovers Entry Descent and Landing and the Use of Aerodynamic Decelerators
Steltzner, Adam; Desai, Prasun; Lee, Wayne; Bruno, Robin
2003-01-01
The Mars Exploration Rovers (MER) project, the next United States mission to the surface of Mars, uses aerodynamic decelerators in during its entry, descent and landing (EDL) phase. These two identical missions (MER-A and MER-B), which deliver NASA s largest mobile science suite to date to the surface of Mars, employ hypersonic entry with an ablative energy dissipating aeroshell, a supersonic/subsonic disk-gap-band parachute and an airbag landing system within EDL. This paper gives an overview of the MER EDL system and speaks to some of the challenges faced by the various aerodynamic decelerators.
Izumi, K. H.; Thompson, J. L.; Groce, J. L.; Schwab, R. W.
1986-01-01
The design requirements for a 4D path definition algorithm are described. These requirements were developed for the NASA ATOPS as an extension of the Local Flow Management/Profile Descent algorithm. They specify the processing flow, functional and data architectures, and system input requirements, and recommended the addition of a broad path revision (reinitialization) function capability. The document also summarizes algorithm design enhancements and the implementation status of the algorithm on an in-house PDP-11/70 computer. Finally, the requirements for the pilot-computer interfaces, the lateral path processor, and guidance and steering function are described.
Molybdenum and phosphorus interact to constrain asymbiotic nitrogen fixation in tropical forests.
Directory of Open Access Journals (Sweden)
Nina Wurzburger
Full Text Available Biological di-nitrogen fixation (N(2 is the dominant natural source of new nitrogen to land ecosystems. Phosphorus (P is thought to limit N(2 fixation in many tropical soils, yet both molybdenum (Mo and P are crucial for the nitrogenase reaction (which catalyzes N(2 conversion to ammonia and cell growth. We have limited understanding of how and when fixation is constrained by these nutrients in nature. Here we show in tropical forests of lowland Panama that the limiting element on asymbiotic N(2 fixation shifts along a broad landscape gradient in soil P, where Mo limits fixation in P-rich soils while Mo and P co-limit in P-poor soils. In no circumstance did P alone limit fixation. We provide and experimentally test a mechanism that explains how Mo and P can interact to constrain asymbiotic N(2 fixation. Fixation is uniformly favored in surface organic soil horizons--a niche characterized by exceedingly low levels of available Mo relative to P. We show that soil organic matter acts to reduce molybdate over phosphate bioavailability, which, in turn, promotes Mo limitation in sites where P is sufficient. Our findings show that asymbiotic N(2 fixation is constrained by the relative availability and dynamics of Mo and P in soils. This conceptual framework can explain shifts in limitation status across broad landscape gradients in soil fertility and implies that fixation depends on Mo and P in ways that are more complex than previously thought.
Towards weakly constrained double field theory
Directory of Open Access Journals (Sweden)
Kanghoon Lee
2016-08-01
Full Text Available We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.
Continuation of Sets of Constrained Orbit Segments
DEFF Research Database (Denmark)
Schilder, Frank; Brøns, Morten; Chamoun, George Chaouki
Sets of constrained orbit segments of time continuous flows are collections of trajectories that represent a whole or parts of an invariant set. A non-trivial but simple example is a homoclinic orbit. A typical representation of this set consists of an equilibrium point of the flow and a trajectory...... that starts close and returns close to this fixed point within finite time. More complicated examples are hybrid periodic orbits of piecewise smooth systems or quasi-periodic invariant tori. Even though it is possible to define generalised two-point boundary value problems for computing sets of constrained...... orbit segments, this is very disadvantageous in practice. In this talk we will present an algorithm that allows the efficient continuation of sets of constrained orbit segments together with the solution of the full variational problem....
Kinetic comparison of older men and women during walk-to-stair descent transition.
Singhal, Kunal; Kim, Jemin; Casebolt, Jeffrey; Lee, Sangwoo; Han, Ki Hoon; Kwon, Young-Hoo
2014-09-01
Stair walking is one of the most challenging tasks for older adults, with women reporting higher incidence of falls. The purpose of this study was to investigate the gender differences in kinetics during stair descent transition. Twenty-eight participants (12 male and 16 female; 68.5 and 69.0 years of mean age, respectively) performed stair descent from level walking in a step-over-step manner at a self-selected speed over a custom-made three-step staircase with embedded force plates. Kinematic and force data were combined using inverse dynamics to generate kinetic data for gender comparison. The top and the first step on the staircase were chosen for analysis. Women showed a higher trail leg peak hip abductor moment (-1.0 Nm/kg), lower trail leg peak knee extensor moment and eccentric power (0.74 Nm/kg and 3.15 W/kg), and lower peak concentric power at trail leg ankle joint (1.29 W/kg) as compared to men (ppredispose women to a higher risk of fall. Copyright © 2014 Elsevier B.V. All rights reserved.
Gaebler, John A.; Tolson, Robert H.
2010-01-01
In the study of entry, descent, and landing, Monte Carlo sampling methods are often employed to study the uncertainty in the designed trajectory. The large number of uncertain inputs and outputs, coupled with complicated non-linear models, can make interpretation of the results difficult. Three methods that provide statistical insights are applied to an entry, descent, and landing simulation. The advantages and disadvantages of each method are discussed in terms of the insights gained versus the computational cost. The first method investigated was failure domain bounding which aims to reduce the computational cost of assessing the failure probability. Next a variance-based sensitivity analysis was studied for the ability to identify which input variable uncertainty has the greatest impact on the uncertainty of an output. Finally, probabilistic sensitivity analysis is used to calculate certain sensitivities at a reduced computational cost. These methods produce valuable information that identifies critical mission parameters and needs for new technology, but generally at a significant computational cost.
Flight Mechanics of the Entry, Descent and Landing of the ExoMars Mission
HayaRamos, Rodrigo; Boneti, Davide
2007-01-01
ExoMars is ESA's current mission to planet Mars. A high mobility rover and a fixed station will be deployed on the surface of Mars. This paper regards the flight mechanics of the Entry, Descent and Landing (EDL) phases used for the mission analysis and design of the Baseline and back-up scenarios of the mission. The EDL concept is based on a ballistic entry, followed by a descent under parachutes and inflatable devices (airbags) for landing. The mission analysis and design is driven by the flexibility in terms of landing site, arrival dates and the very stringent requirement in terms of landing accuracy. The challenging requirements currently imposed to the mission need innovative analysis and design techniques to support system design trade-offs to cope with the variability in entry conditions. The concept of the Global Entry Corridor has been conceived, designed, implemented and successfully validated as a key tool to provide a global picture of the mission capabilities in terms of landing site reachability.
Dictionary Learning Based on Nonnegative Matrix Factorization Using Parallel Coordinate Descent
Directory of Open Access Journals (Sweden)
Zunyi Tang
2013-01-01
Full Text Available Sparse representation of signals via an overcomplete dictionary has recently received much attention as it has produced promising results in various applications. Since the nonnegativities of the signals and the dictionary are required in some applications, for example, multispectral data analysis, the conventional dictionary learning methods imposed simply with nonnegativity may become inapplicable. In this paper, we propose a novel method for learning a nonnegative, overcomplete dictionary for such a case. This is accomplished by posing the sparse representation of nonnegative signals as a problem of nonnegative matrix factorization (NMF with a sparsity constraint. By employing the coordinate descent strategy for optimization and extending it to multivariable case for processing in parallel, we develop a so-called parallel coordinate descent dictionary learning (PCDDL algorithm, which is structured by iteratively solving the two optimal problems, the learning process of the dictionary and the estimating process of the coefficients for constructing the signals. Numerical experiments demonstrate that the proposed algorithm performs better than the conventional nonnegative K-SVD (NN-KSVD algorithm and several other algorithms for comparison. What is more, its computational consumption is remarkably lower than that of the compared algorithms.
Eyelid fissure dimensions in Japanese and in Brazilians of European descent over 50 years of age.
Viveiros, Magda Massae Hata; Matai, Olívia; Takahagi, Rodrigo Ueno; Padovani, Carlos Roberto; Schellini, Silvana Artioli
2017-01-01
To investigate differences in the palpebral fissure eyelid position in Japanese subjects and in Brazilian subjects of European descent over 50 years of age. A cross-sectional study evaluating 50 Japanese subjects and 50 Bra---zilian subjects of European descent over 50 years of age was performed to evaluate the effect of aging on eyelid position. Digital photographs were taken with the eyes in the primary position and transferred to a computer to be processed by Scion imaging software for evaluation of palpebral fissure width, height, and margin reflex distance (MRD). The data were statistically analyzed according to sex, age, and race. The width of the eyelid fissure in Japanese subjects was higher than that in Brazilian subjects, whereas the height of the eyelid fissure and the MRD1 was higher in Brazilians than in Japanese (pMRD1 were linearly associated with age only in the Japanese group (p0.05). There are racial differences in age-related changes in the eyelids, which are more marked in Japanese subjects.
Eyelid fissure dimensions in Japanese and in Brazilians of European descent over 50 years of age
Directory of Open Access Journals (Sweden)
Magda Massae Hata Viveiros
Full Text Available ABSTRACT Purpose: To investigate differences in the palpebral fissure eyelid position in Japanese subjects and in Brazilian subjects of European descent over 50 years of age. Methods: A cross-sectional study evaluating 50 Japanese subjects and 50 Brazilian subjects of European descent over 50 years of age was performed to evaluate the effect of aging on eyelid position. Digital photographs were taken with the eyes in the primary position and transferred to a computer to be processed by Scion imaging software for evaluation of palpebral fissure width, height, and margin reflex distance (MRD. The data were statistically analyzed according to sex, age, and race. Results: The width of the eyelid fissure in Japanese subjects was higher than that in Brazilian subjects, whereas the height of the eyelid fissure and the MRD1 was higher in Brazilians than in Japanese (p0.05. Conclusion: There are racial differences in age-related changes in the eyelids, which are more marked in Japanese subjects.
Fragment angular momenta and descent dynamics in sup 2 sup 5 sup 2 Cf spontaneous fission
Popeko, J S; Ter-Akopian, G M
2002-01-01
Average angular momentum values of primary fission fragments as a function of neutron multiplicity and neutron-to-proton ratio were extracted for the first time for the Mo-Ba and Zr-Ce charge splittings of sup 2 sup 5 sup 2 Cf. The results are discussed in terms of the energy balance occurring at the scission point. For the first time we show that for large fragment elongation associated with larger numbers of evaporated neutrons (v sub t sub o sub t >=6), essentially only zero point bending oscillation takes places, i.e. T = 0 for this degree of freedom. For the major part of the fission events, with v sub t sub o sub t = 2-5, the banding oscillation is excited to a temperature of 2-3 MeV. Such a high bending temperature implies that the coupling between the collective and internal degrees of freedom is weak at the descent of the even-even nucleus of sup 2 sup 5 sup 2 Cf to the scission point. The dipole oscillations occurring at the descent take away some 2.5 - 3.0 MeV from the release energy. A correlation...
Differences in ocular blood flow in glaucoma between patients of African and European descent.
Siesky, Brent; Harris, Alon; Racette, Lyne; Abassi, Rania; Chandrasekhar, Kaarthik; Tobe, Leslie A; Behzadi, Jennifer; Eckert, George; Amireskandari, Annahita; Muchnik, Michael
2015-02-01
To investigate differences in ocular blood flow in individuals of African descent (AD) and European descent (ED) with open angle glaucoma (OAG). A retrospective data analysis was performed on OAG patients of AD and ED who were previously examined for ocular blood flow within the Department of Ophthalmology at Indiana University School of Medicine. Data analysis included blood pressure, heart rate, visual fields, intraocular pressure, ocular perfusion pressure, and color Doppler imaging of retrobulbar vessels. Color Doppler imaging measurements were performed on ophthalmic, central retinal, and nasal and temporal short posterior ciliary arteries, with peak systolic (PSV) and end diastolic velocities (EDV) as well as the Pourcelot vascular resistive index calculated for each vessel. Two-sample t tests of unequal variance were performed with P values <0.05 considered statistically significant. OAG patients of AD had statistically significant lower retrobulbar blood flow values than patients of ED including lower ophthalmic artery PSV (P=0.0001), ophthalmic artery EDV (P=0.0008), central retinal artery PSV (P=0.01), temporal short posterior ciliary artery PSV (P=0.0037), and nasal short posterior ciliary artery PSV (P<0.0001). No significant differences were found in terms of intraocular pressure or visual field parameters. Significantly lower blood flow values were identified in all retrobulbar blood vessels in AD compared with ED OAG patients. These findings suggest that the contribution of ocular blood flow to the disease process may be different in AD compared with ED OAG patients.
Modeling Atmospheric CO2 Processes to Constrain the Missing Sink
Kawa, S. R.; Denning, A. S.; Erickson, D. J.; Collatz, J. C.; Pawson, S.
2005-01-01
We report on a NASA supported modeling effort to reduce uncertainty in carbon cycle processes that create the so-called missing sink of atmospheric CO2. Our overall objective is to improve characterization of CO2 source/sink processes globally with improved formulations for atmospheric transport, terrestrial uptake and release, biomass and fossil fuel burning, and observational data analysis. The motivation for this study follows from the perspective that progress in determining CO2 sources and sinks beyond the current state of the art will rely on utilization of more extensive and intensive CO2 and related observations including those from satellite remote sensing. The major components of this effort are: 1) Continued development of the chemistry and transport model using analyzed meteorological fields from the Goddard Global Modeling and Assimilation Office, with comparison to real time data in both forward and inverse modes; 2) An advanced biosphere model, constrained by remote sensing data, coupled to the global transport model to produce distributions of CO2 fluxes and concentrations that are consistent with actual meteorological variability; 3) Improved remote sensing estimates for biomass burning emission fluxes to better characterize interannual variability in the atmospheric CO2 budget and to better constrain the land use change source; 4) Evaluating the impact of temporally resolved fossil fuel emission distributions on atmospheric CO2 gradients and variability. 5) Testing the impact of existing and planned remote sensing data sources (e.g., AIRS, MODIS, OCO) on inference of CO2 sources and sinks, and use the model to help establish measurement requirements for future remote sensing instruments. The results will help to prepare for the use of OCO and other satellite data in a multi-disciplinary carbon data assimilation system for analysis and prediction of carbon cycle changes and carbodclimate interactions.
Constrained principal component analysis and related techniques
Takane, Yoshio
2013-01-01
In multivariate data analysis, regression techniques predict one set of variables from another while principal component analysis (PCA) finds a subspace of minimal dimensionality that captures the largest variability in the data. How can regression analysis and PCA be combined in a beneficial way? Why and when is it a good idea to combine them? What kind of benefits are we getting from them? Addressing these questions, Constrained Principal Component Analysis and Related Techniques shows how constrained PCA (CPCA) offers a unified framework for these approaches.The book begins with four concre
Polyacrylamide temperature gradient gel electrophoresis.
Viglasky, Viktor
2013-01-01
Temperature Gradient Gel Electrophoresis (TGGE) is a form of electrophoresis in which temperature gradient is used to denature molecules as they move through either acrylamide or agarose gel. TGGE can be applied to analyze DNA, RNA, protein-DNA complexes, and, less commonly, proteins. Separation of double-stranded DNA molecules during TGGE relies on temperature-dependent melting of the DNA duplex into two single-stranded DNA molecules. Therefore, the mobility of DNA reflects not only the size of the molecule but also its nucleotide composition, thereby allowing separation of DNA molecules of similar size with different sequences. Depending on the relative orientation of electric field and temperature gradient, TGGE can be performed in either a parallel or a perpendicular mode. The former is used to analyze multiple samples in the same gel, whereas the later allows detailed analysis of a single sample. This chapter is focused on analysis of DNA by polyacrylamide TGGE using the perpendicular mode.
Ryan, Niall J.; Kinnison, Douglas E.; Garcia, Rolando R.; Hoffmann, Christoph G.; Palm, Mathias; Raffalski, Uwe; Notholt, Justus
2018-02-01
We investigate the reliability of using trace gas measurements from remote sensing instruments to infer polar atmospheric descent rates during winter within 46-86 km altitude. Using output from the Specified Dynamics Whole Atmosphere Community Climate Model (SD-WACCM) between 2008 and 2014, tendencies of carbon monoxide (CO) volume mixing ratios (VMRs) are used to assess a common assumption of dominant vertical advection of tracers during polar winter. The results show that dynamical processes other than vertical advection are not negligible, meaning that the transport rates derived from trace gas measurements do not represent the mean descent of the atmosphere. The relative importance of vertical advection is lessened, and exceeded by other processes, during periods directly before and after a sudden stratospheric warming, mainly due to an increase in eddy transport. It was also found that CO chemistry cannot be ignored in the mesosphere due to the night-time layer of OH at approximately 80 km altitude. CO VMR profiles from the Kiruna Microwave Radiometer and the Microwave Limb Sounder were compared to SD-WACCM output, and show good agreement on daily and seasonal timescales. SD-WACCM CO profiles are combined with the CO tendencies to estimate errors involved in calculating the mean descent of the atmosphere from remote sensing measurements. The results indicate errors on the same scale as the calculated descent rates, and that the method is prone to a misinterpretation of the direction of air motion. The true rate of atmospheric descent is seen to be masked by processes, other than vertical advection, that affect CO. We suggest an alternative definition of the rate calculated using remote sensing measurements: not as the mean descent of the atmosphere, but as an effective rate of vertical transport for the trace gas under observation.
Directory of Open Access Journals (Sweden)
Weijian Si
2015-01-01
Full Text Available A novel direction of arrival (DOA estimation method in compressed sensing (CS is proposed, in which the DOA estimation problem is cast as the joint sparse reconstruction from multiple measurement vectors (MMV. The proposed method is derived through transforming quadratically constrained linear programming (QCLP into unconstrained convex optimization which overcomes the drawback that l1-norm is nondifferentiable when sparse sources are reconstructed by minimizing l1-norm. The convergence rate and estimation performance of the proposed method can be significantly improved, since the steepest descent step and Barzilai-Borwein step are alternately used as the search step in the unconstrained convex optimization. The proposed method can obtain satisfactory performance especially in these scenarios with low signal to noise ratio (SNR, small number of snapshots, or coherent sources. Simulation results show the superior performance of the proposed method as compared with existing methods.
Thermoregulation constrains effective warning signal expression.
Lindstedt, Carita; Lindström, Leena; Mappes, Johanna
2009-02-01
Evolution of conspicuous signals may be constrained if animal coloration has nonsignaling as well as signaling functions. In aposematic wood tiger moth (Parasemia plantaginis) larvae, the size of a warning signal (orange patch on black body) varies phenotypically and genetically. Although a large warning signal is favored as an antipredator defense, we hypothesized that thermoregulation may constrain the signal size in colder habitats. To test this hypothesis, we conducted a factorial rearing experiment with two selection lines for larval coloration (small and large signal) and with two temperature manipulations (high and low temperature environment). Temperature constrained the size and brightness of the warning signal. Larvae with a small signal had an advantage in the colder environment, which was demonstrated by a faster development time and growth rate in the low temperature treatment, compared to larvae with a large signal. Interestingly, the larvae with a small signal were found more often on the plant than the ones with a large signal, suggesting higher basking activity of the melanic (small signal) individuals in the low temperature. We conclude that the expression of aposematic display is not only defined by its efficacy against predators; variation in temperature may constrain evolution of a conspicuous warning signal and maintain variation in it.
Integrating job scheduling and constrained network routing
DEFF Research Database (Denmark)
Gamst, Mette
2010-01-01
This paper examines the NP-hard problem of scheduling jobs on resources such that the overall profit of executed jobs is maximized. Job demand must be sent through a constrained network to the resource before execution can begin. The problem has application in grid computing, where a number...
Constrained analysis of topologically massive gravity
Energy Technology Data Exchange (ETDEWEB)
Barcelos-Neto, J. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Fisica; Dargam, T.G. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Inst. de Fisica
1995-08-01
We quantize the Einstein gravity in the formalism of weak gravitational fields by using the constrained Hamiltonian method. Special emphasis is given to the 2+1 spacetime dimensional case where a (topological) Chern-Simons term is added to the Lagrangian. (orig.)
Neutron Powder Diffraction and Constrained Refinement
DEFF Research Database (Denmark)
Pawley, G. S.; Mackenzie, Gordon A.; Dietrich, O. W.
1977-01-01
The first use of a new program, EDINP, is reported. This program allows the constrained refinement of molecules in a crystal structure with neutron diffraction powder data. The structures of p-C6F4Br2 and p-C6F4I2 are determined by packing considerations and then refined with EDINP. Refinement...
On Tree-Constrained Matchings and Generalizations
S. Canzar (Stefan); K. Elbassioni; G.W. Klau (Gunnar); J. Mestre
2011-01-01
htmlabstractWe consider the following \\textsc{Tree-Constrained Bipartite Matching} problem: Given two rooted trees $T_1=(V_1,E_1)$, $T_2=(V_2,E_2)$ and a weight function $w: V_1\\times V_2 \\mapsto \\mathbb{R}_+$, find a maximum weight matching $\\mathcal{M}$ between nodes of the two trees, such that
Client's constraining factors to construction project management ...
African Journals Online (AJOL)
This study analyzed client's related factors that constrain project management success of public and private sector construction in Nigeria. Issues that concern clients in any project can not be undermined as they are the owners and the initiators of project proposals. It is assumed that success, failure or abandonment of ...
Constrained tri-sphere kinematic positioning system
Viola, Robert J
2010-12-14
A scalable and adaptable, six-degree-of-freedom, kinematic positioning system is described. The system can position objects supported on top of, or suspended from, jacks comprising constrained joints. The system is compatible with extreme low temperature or high vacuum environments. When constant adjustment is not required a removable motor unit is available.
A model for optimal constrained adaptive testing
van der Linden, Willem J.; Reese, Lynda M.
1997-01-01
A model for constrained computerized adaptive testing is proposed in which the information in the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum
Modeling the microstructural evolution during constrained sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.
A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural respon...
Constrained Registration of the Wrist Joint
Van de Giessen, M.; Streekstra, G.J.; Strackee, S.D.; Maas, M.; Grimbergen, K.A.; Van Vliet, L.J.; Vos, F.M.
2009-01-01
Comparing wrist shapes of different individuals requires alignment of these wrists into the same pose. Unconstrained registration of the carpal bones results in anatomically nonfeasible wrists. In this paper, we propose to constrain the registration using the shapes of adjacent bones, by keeping the
Constrained registration of the wrist joint
van de Giessen, M.; Streekstra, G.J.; Strackee, S.D.; Maas, M.; Grimbergen, K.A.; van Vliet, L.J.; Vos, F.M.
2009-01-01
Comparing wrist shapes of different individuals requires alignment of these wrists into the same pose. Unconstrained registration of the carpal bones results in anatomically nonfeasible wrists. In this paper, we propose to constrain the registration using the shapes of adjacent bones, by keeping the
Modeling the Microstructural Evolution During Constrained Sintering
DEFF Research Database (Denmark)
Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini
2015-01-01
A numerical model able to simulate solid-state constrained sintering is presented. The model couples an existing kinetic Monte Carlo model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress as ...
A model for optimal constrained adaptive testing
van der Linden, Willem J.; Reese, Lynda M.
2001-01-01
A model for constrained computerized adaptive testing is proposed in which the information on the test at the ability estimate is maximized subject to a large variety of possible constraints on the contents of the test. At each item-selection step, a full test is first assembled to have maximum
Models of Flux Tubes from Constrained Relaxation
Indian Academy of Sciences (India)
tribpo
J. Astrophys. Astr. (2000) 21, 299 302. Models of Flux Tubes from Constrained Relaxation. Α. Mangalam* & V. Krishan†, Indian Institute of Astrophysics, Koramangala,. Bangalore 560 034, India. *e mail: mangalam @ iiap. ernet. in. † e mail: vinod@iiap.ernet.in. Abstract. We study the relaxation of a compressible plasma to ...
Constrained systems described by Nambu mechanics
International Nuclear Information System (INIS)
Lassig, C.C.; Joshi, G.C.
1996-01-01
Using the framework of Nambu's generalised mechanics, we obtain a new description of constrained Hamiltonian dynamics, involving the introduction of another degree of freedom in phase space, and the necessity of defining the action integral on a world sheet. We also discuss the problem of quantizing Nambu mechanics. (authors). 5 refs
Computational Strain Gradient Crystal Plasticity
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Kysar, Jeffrey W.
2011-01-01
element solution method is presented, which delivers the slip-rate field and the velocity-field based on two minimum principles. Some plane deformation problems relevant for certain specific orientations of a face centered cubic crystal under plane loading conditions are studied, and effective in......A model for strain gradient crystal visco-plasticity is formulated along the lines proposed by Fleck andWillis (2009) for isotropic plasticity. Size-effects are included in the model due to the addition of gradient terms in both the free energy as well as through a dissipation potential. A finite...
Ferri, F.; Karatekin, O.; Aboudan, A.; VanHove, B.; Colombatti, C.; Bettanini, C.; Debei, S.; Lewis, S.; Forget, F.
2017-09-01
On the 19th October 2016, Schiaparelli, the Entry Demonstrator Module (EDM) of the ESA ExoMars Program entered into the martian atmosphere. Although it did not complete a safe landing on Mars, it transmitted data throughout its descent to the surface, until the loss of signal at 1 minute before the expected touch-down on Mars' surface. From the flight data, we reconstruct the actual dynamics of the vehicle during its descent towards Mars's surface and retrieve the atmospheric profile, in terms of density, pressure and temperature, along its trajectory for atmospheric investigations.
Constrained target controllability of complex networks
Guo, Wei-Feng; Zhang, Shao-Wu; Wei, Ze-Gang; Zeng, Tao; Liu, Fei; Zhang, Jingsong; Wu, Fang-Xiang; Chen, Luonan
2017-06-01
It is of great theoretical interest and practical significance to study how to control a system by applying perturbations to only a few driver nodes. Recently, a hot topic of modern network researches is how to determine driver nodes that allow the control of an entire network. However, in practice, to control a complex network, especially a biological network, one may know not only the set of nodes which need to be controlled (i.e. target nodes), but also the set of nodes to which only control signals can be applied (i.e. constrained control nodes). Compared to the general concept of controllability, we introduce the concept of constrained target controllability (CTC) of complex networks, which concerns the ability to drive any state of target nodes to their desirable state by applying control signals to the driver nodes from the set of constrained control nodes. To efficiently investigate the CTC of complex networks, we further design a novel graph-theoretic algorithm called CTCA to estimate the ability of a given network to control targets by choosing driver nodes from the set of constrained control nodes. We extensively evaluate the CTC of numerous real complex networks. The results indicate that biological networks with a higher average degree are easier to control than biological networks with a lower average degree, while electronic networks with a lower average degree are easier to control than web networks with a higher average degree. We also show that our CTCA can more efficiently produce driver nodes for target-controlling the networks than existing state-of-the-art methods. Moreover, we use our CTCA to analyze two expert-curated bio-molecular networks and compare to other state-of-the-art methods. The results illustrate that our CTCA can efficiently identify proven drug targets and new potentials, according to the constrained controllability of those biological networks.
Tovbis, Alexander; Venakides, Stephanos
2010-04-01
The initial value problem for an integrable system, such as the Nonlinear Schrödinger equation, is solved by subjecting the linear eigenvalue problem arising from its Lax pair to inverse scattering, and, thus, transforming it to a matrix Riemann-Hilbert problem (RHP) in the spectral variable. In the semiclassical limit, the method of nonlinear steepest descent ([4,5]), supplemented by the g-function mechanism ([3]), is applied to this RHP to produce explicit asymptotic solution formulae for the integrable system. These formule are based on a hyperelliptic Riemann surface {mathcal {R} = mathcal {R}(x,t)} in the spectral variable, where the space-time variables ( x, t) play the role of external parameters. The curves in the x, t plane, separating regions of different genuses of {mathcal {R}(x,t)}, are called breaking curves or nonlinear caustics. The genus of {mathcal {R}(x,t)} is related to the number of oscillatory phases in the asymptotic solution of the integrable system at the point x, t. The evolution theorem ([10]) guarantees continuous evolution of the asymptotic solution in the space-time away from the breaking curves. In the case of the analytic scattering data f( z; x, t) (in the NLS case, f is a normalized logarithm of the reflection coefficient with time evolution included), the primary role in the breaking mechanism is played by a phase function {{Im h(z;x,t)}}, which is closely related to the g function. Namely, a break can be caused ([10]) either through the change of topology of zero level curves of {Im h(z;x,t)} (regular break), or through the interaction of zero level curves of {{Im h(z;x,t)}} with singularities of f (singular break). Every time a breaking curve in the x, t plane is reached, one has to prove the validity of the nonlinear steepest descent asymptotics in the region across the curve. In this paper we prove that in the case of a regular break, the nonlinear steepest descent asymptotics can be “automatically” continued through the
New convergence results for the scaled gradient projection method
Bonettini, S.; Prato, M.
2015-09-01
The aim of this paper is to deepen the convergence analysis of the scaled gradient projection (SGP) method, proposed by Bonettini et al in a recent paper for constrained smooth optimization. The main feature of SGP is the presence of a variable scaling matrix multiplying the gradient, which may change at each iteration. In the last few years, extensive numerical experimentation showed that SGP equipped with a suitable choice of the scaling matrix is a very effective tool for solving large scale variational problems arising in image and signal processing. In spite of the very reliable numerical results observed, only a weak convergence theorem is provided establishing that any limit point of the sequence generated by SGP is stationary. Here, under the only assumption that the objective function is convex and that a solution exists, we prove that the sequence generated by SGP converges to a minimum point, if the scaling matrices sequence satisfies a simple and implementable condition. Moreover, assuming that the gradient of the objective function is Lipschitz continuous, we are also able to prove the {O}(1/k) convergence rate with respect to the objective function values. Finally, we present the results of a numerical experience on some relevant image restoration problems, showing that the proposed scaling matrix selection rule performs well also from the computational point of view.
Compositional gradients in Gramineae genes
DEFF Research Database (Denmark)
Wong, Gane Ka-Shu; Wang, Jun; Tao, Lin
2002-01-01
In this study, we describe a property of Gramineae genes, and perhaps all monocot genes, that is not observed in eudicot genes. Along the direction of transcription, beginning at the junction of the 5'-UTR and the coding region, there are gradients in GC content, codon usage, and amino-acid usage...
Jans, S. M. P. J.; Daemers, D. O. A.; de Vos, R.; Lagro-Jansen, A. L. M.
2009-01-01
to investigate the prevalence of anaemia in pregnancy according to the cut-off points used in the national clinical guideline 'Anaemia in Primary Care Midwifery Practice', and to investigate a possible difference in prevalence between pregnant women of Northern European descent compared with women
Uncovering the fuzzy community structure accurately based on steepest descent projection
Fang, Changjian; Mu, Dejun; Deng, Zhenghong; Yan, Jiaqi
2017-09-01
Uncovering the community structure in complex network is a hot research point in recent years. How to identify the community structure accurately in complex network is still an open question under research. There are lots of methods based on topological information, which have some good performances at the expense of longer runtimes. In this paper, we propose a new fuzzy algorithm which follows the line of fuzzy c-means algorithm. A steepest descent framework with projection by optimizing the quality function is presented under the generalized framework. The results of experiments on both real-world networks and synthetic networks show that the proposed method achieves the highest efficiency and is easy for detecting fuzzy community structure in large-scale complex networks.
Rosas, Lisa G.; Guendelman, Sylvia; Harley, Kim; Fernald, Lia C. H.; Neufeld, Lynnette; Mejia, Fabiola
2010-01-01
The prevalence of childhood obesity is high among young children of Mexican origin in the United States, however, the determinants are poorly understood. We conducted a binational study with a sample from California (CA) and Mexico (MX), to identify and compare the most important factors associated with overweight and obesity among children of Mexican descent. Significantly more children were classified as overweight or obese in CA compared to MX (53.3 vs. 14.9%, P obese mother was significantly associated with being overweight or obese. In MX, male gender, high socioeconomic status and very low food insecurity were associated with being overweight or obese. These data offer hypotheses for how migration may influence the high prevalence of overweight among the Mexican children in California. PMID:20217234
Cheatwood, F. McNeil; Bose, Deepak; Karlgaard, Christopher D.; Kuhl, Christopher A.; Santos, Jose A.; Wright, Michael J.
2014-01-01
The Mars Science Laboratory (MSL) entry vehicle (EV) successfully entered the Mars atmosphere and landed the Curiosity rover safely on the surface of the planet in Gale crater on August 6, 2012. MSL carried the MSL Entry, Descent, and Landing (EDL) Instrumentation (MEDLI). MEDLI delivered the first in-depth understanding of the Mars entry environments and the response of the entry vehicle to those environments. MEDLI was comprised of three major subsystems: the Mars Entry Atmospheric Data System (MEADS), the MEDLI Integrated Sensor Plugs (MISP), and the Sensor Support Electronics (SSE). Ultimately, the entire MEDLI sensor suite consisting of both MEADS and MISP provided measurements that were used for trajectory reconstruction and engineering validation of aerodynamic, atmospheric, and thermal protection system (TPS) models in addition to Earth-based systems testing procedures. This report contains in-depth hardware descriptions, performance evaluation, and data information of the three MEDLI subsystems.
A Multidisciplinary Tool for Systems Analysis of Planetary Entry, Descent, and Landing (SAPE)
Samareh, Jamshid A.
2009-01-01
SAPE is a Python-based multidisciplinary analysis tool for systems analysis of planetary entry, descent, and landing (EDL) for Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. The purpose of SAPE is to provide a variable-fidelity capability for conceptual and preliminary analysis within the same framework. SAPE includes the following analysis modules: geometry, trajectory, aerodynamics, aerothermal, thermal protection system, and structural sizing. SAPE uses the Python language-a platform-independent open-source software for integration and for the user interface. The development has relied heavily on the object-oriented programming capabilities that are available in Python. Modules are provided to interface with commercial and government off-the-shelf software components (e.g., thermal protection systems and finite-element analysis). SAPE runs on Microsoft Windows and Apple Mac OS X and has been partially tested on Linux.
A coordinate descent MM algorithm for fast computation of sparse logistic PCA
Lee, Seokho
2013-06-01
Sparse logistic principal component analysis was proposed in Lee et al. (2010) for exploratory analysis of binary data. Relying on the joint estimation of multiple principal components, the algorithm therein is computationally too demanding to be useful when the data dimension is high. We develop a computationally fast algorithm using a combination of coordinate descent and majorization-minimization (MM) auxiliary optimization. Our new algorithm decouples the joint estimation of multiple components into separate estimations and consists of closed-form elementwise updating formulas for each sparse principal component. The performance of the proposed algorithm is tested using simulation and high-dimensional real-world datasets. © 2013 Elsevier B.V. All rights reserved.
Quantification of Plume-Soil Interaction and Excavation Due to the Sky Crane Descent Stage
Vizcaino, Jeffrey; Mehta, Manish
2015-01-01
The quantification of the particulate erosion that occurs as a result of a rocket exhaust plume impinging on soil during extraterrestrial landings is critical for future robotic and human lander mission design. The aerodynamic environment that results from the reflected plumes results in dust lifting, site alteration and saltation, all of which create a potentially erosive and contaminant heavy environment for the lander vehicle and any surrounding structures. The Mars Science Lab (MSL), weighing nearly one metric ton, required higher levels of thrust from its retro propulsive systems and an entirely new descent system to minimize these effects. In this work we seek to quantify plume soil interaction and its resultant soil erosion caused by the MSL's Sky Crane descent stage engines by performing three dimensional digital terrain and elevation mapping of the Curiosity rover's landing site. Analysis of plume soil interaction altitude and time was performed by detailed examination of the Mars Descent Imager (MARDI) still frames and reconstructed inertial measurement unit (IMU) sensor data. Results show initial plume soil interaction from the Sky Crane's eight engines began at ground elevations greater than 60 meters and more than 25 seconds before the rovers' touchdown event. During this time, viscous shear erosion (VSE) was dominant typically resulting in dusting of the surface with flow propagating nearly parallel to the surface. As the vehicle descended and decreased to four powered engines plume-plume and plume soil interaction increased the overall erosion rate at the surface. Visibility was greatly reduced at a height of roughly 20 meters above the surface and fell to zero ground visibility shortly after. The deployment phase of the Sky Crane descent stage hovering at nearly six meters above the surface showed the greatest amount of erosion with several large particles of soil being kicked up, recirculated, and impacting the bottom of the rover chassis. Image
Genetic drift. Descent, lineage, and pedigree of the Trojans in Homer's Iliad.
Bazopoulou-Kyrkanidou, Euterpe
2007-12-15
Homer's Iliad, is an epic poem that describes the last 70 days of the Trojan War, which was waged against the city of Troy by the Achaeans. Here, the descent, lineage, and the pedigree of the Trojans are presented. In the Illiad, they are said to have originated from Zeus. Beginning with him, the Trojan pedigree comprised 17 men in 8 generations with Dardanus, founder of Dardania in the second generation; Tros, King of the Trojans in the fourth generation; and the two heroes Hector and Aeneas in the eighth generation. In the seventh generation, Priam, as King of the Trojans, had a huge family, including 50 sons: 19 children with his wife Hecabe, other sons with many different wives, and some daughters as well. Hector, the first born, became leader of the Trojans. Hector's brother, Paris, in abducting Helen of Sparta, the wife of King Menelaus, caused the Trojan War to break out. (c) 2007 Wiley-Liss, Inc.
Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis, Phase 2 Results
Murri, Daniel G.
2011-01-01
The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL-Systems Analysis (SA) team that is conducting studies of the technologies and architectures that are required to enable human and higher mass robotic missions to Mars. The findings, observations, and recommendations from the NESC are provided in this report.
Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis. Volume 2; Appendices
Murri, Daniel G.
2010-01-01
The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II (POST2) simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL Systems Analysis (EDL-SA) team, that is conducting studies of the technologies and architectures that are required to enable higher mass robotic and human mission to Mars. The appendices to the original report are contained in this document.
Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis. Volume 1
Murri, Daniel G.
2010-01-01
The NASA Engineering and Safety Center (NESC) was requested to establish the Simulation Framework for Rapid Entry, Descent, and Landing (EDL) Analysis assessment, which involved development of an enhanced simulation architecture using the Program to Optimize Simulated Trajectories II (POST2) simulation tool. The assessment was requested to enhance the capability of the Agency to provide rapid evaluation of EDL characteristics in systems analysis studies, preliminary design, mission development and execution, and time-critical assessments. Many of the new simulation framework capabilities were developed to support the Agency EDL Systems Analysis (EDL-SA) team, that is conducting studies of the technologies and architectures that are required to enable higher mass robotic and human mission to Mars. The findings of the assessment are contained in this report.
Parametric Mass Modeling for Mars Entry, Descent and Landing System Analysis Study
Samareh, Jamshid A.; Komar, D. R.
2011-01-01
This paper provides an overview of the parametric mass models used for the Entry, Descent, and Landing Systems Analysis study conducted by NASA in FY2009-2010. The study examined eight unique exploration class architectures that included elements such as a rigid mid-L/D aeroshell, a lifting hypersonic inflatable decelerator, a drag supersonic inflatable decelerator, a lifting supersonic inflatable decelerator implemented with a skirt, and subsonic/supersonic retro-propulsion. Parametric models used in this study relate the component mass to vehicle dimensions and mission key environmental parameters such as maximum deceleration and total heat load. The use of a parametric mass model allows the simultaneous optimization of trajectory and mass sizing parameters.
Natural selection and the distribution of identity-by-descent in the human genome
DEFF Research Database (Denmark)
Albrechtsen, Anders; Moltke, Ida; Nielsen, Rasmus
2010-01-01
There has recently been considerable interest in detecting natural selection in the human genome. Selection will usually tend to increase identity-by-descent (IBD) among individuals in a population, and many methods for detecting recent and ongoing positive selection indirectly take advantage...... of this. In this article we show that excess IBD sharing is a general property of natural selection and we show that this fact makes it possible to detect several types of selection including a type that is otherwise difficult to detect: selection acting on standing genetic variation. Motivated by this......, we use a recently developed method for identifying IBD sharing among individuals from genome-wide data to scan populations from the new HapMap phase 3 project for regions with excess IBD sharing in order to identify regions in the human genome that have been under strong, very recent selection...
Testosterone secretion during gubernacular development and testicular descent in the dog.
Baumans, V; Dieleman, S J; Wouterse, H S; van Tol, L; Dijkstra, G; Wensing, C J
1985-01-01
Serum testosterone concentrations ranged from 0.24 to 1.45 nmol/l between Day 53 post coitum (p.c.) until Day 40 post partum (p.p.) and did not show variations that could be correlated with the process of testicular descent. The intratesticular androgen appeared to be mainly testosterone, its concentration being about 5000-fold higher than that in serum whereas 5 alpha-dihydrotestosterone could not be demonstrated. The intratesticular testosterone concentration at the initiation of gubernacular regression (Day 0) was apparently, but not significantly, higher than at Day 49 p.c. and at Day 40 p.p. The ability of the neonatal canine testis to synthesize testosterone was indicated by increased serum testosterone concentrations after hCG stimulation.
On the Use of a Range Trigger for the Mars Science Laboratory Entry Descent and Landing
Way, David W.
2011-01-01
In 2012, during the Entry, Descent, and Landing (EDL) of the Mars Science Laboratory (MSL) entry vehicle, a 21.5 m Viking-heritage, Disk-Gap-Band, supersonic parachute will be deployed at approximately Mach 2. The baseline algorithm for commanding this parachute deployment is a navigated planet-relative velocity trigger. This paper compares the performance of an alternative range-to-go trigger (sometimes referred to as Smart Chute ), which can significantly reduce the landing footprint size. Numerical Monte Carlo results, predicted by the POST2 MSL POST End-to-End EDL simulation, are corroborated and explained by applying propagation of uncertainty methods to develop an analytic estimate for the standard deviation of Mach number. A negative correlation is shown to exist between the standard deviations of wind velocity and the planet-relative velocity at parachute deploy, which mitigates the Mach number rise in the case of the range trigger.
A variable neighborhood descent based heuristic to solve the capacitated location-routing problem
Directory of Open Access Journals (Sweden)
M. S. Jabal-Ameli
2011-01-01
Full Text Available Location-routing problem (LRP is established as a new research area in the context of location analysis. The primary concern of LRP is on locating facilities and routing of vehicles among established facilities and existing demand points. In this work, we address the capacitated LRP which arises in many practical applications within logistics and supply chain management. The objective is to minimize the overall system costs which include the fixed costs of opening depots and using vehicles at each depot site, and the variable costs associated with delivery activities. A novel heuristic is proposed which is based on variable neighborhood descent (VND algorithm to solve the resulted problem. The computational study indicates that the proposed VND based heuristic is highly competitive with the existing solution algorithms in terms of solution quality.
Control law synthesis and stability robustness improvement using constrained optimization techniques
Mukhopadhyay, Vivekananda
1990-01-01
The present generic optimization procedure for a continuous or discrete control law (of arbitrary order), which will be applicable to a multiinput-multioutput system, is upon constraining used to satisfy conflicting design requirements on the mean-square responses and stability robustness at the plant input and output. The synthesis procedure is especially suitable for flexible airframes and large space structures modeled by a high-order state-space system of equations. Analytical expressions are obtained for the gradients of the cost function, together with design constraints on the mean-square response and minimum singular value.
Mars 2020 Entry, Descent, and Landing Instrumentation 2 (MEDLI2) Sensor Suite
Hwang, Helen; Wright, Henry; Kuhl, Chris; Schoenenberger, Mark; White, Todd; Karlgaard, Chris; Mahzari, Milad; Oishi, Tomo; Pennington, Steve; Trombetta, Nick;
2017-01-01
The Mars 2020 Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite seeks to address the aerodynamic, aerothermodynamic, and thermal protection system (TPS) performance issues during atmospheric entry, descent, and landing of the Mars 2020 mission. Based on the highly successful instrumentation suite that flew on Mars Science Laboratory (MEDLI), the new sensor suite expands on the types of measurements and also seeks to answer questions not fully addressed by the previous mission. Sensor Package: MEDLI2 consists of 7 pressure transducers, 17 thermal plugs, 2 heat flux sensors, and one radiometer. The sensors are distributed across both the heatshield and backshell, unlike MEDLI (the first sensor suite), which was located solely on the heat-shield. The sensors will measure supersonic pressure on the forebody, a pressure measurement on the aftbody, near-surface and in-depth temperatures in the heatshield and backshell TPS materials, direct total heat flux on the aftbody, and direct radiative heating on the aftbody. Instrument Development: The supersonic pressure transducers, the direct heat flux sensors, and the radiometer all were tested during the development phase. The status of these sensors, including the piezo-resistive pressure sensors, will be presented. The current plans for qualification and calibration for all of the sensors will also be discussed. Post-Flight Data Analysis: Similar to MEDLI, the estimated flight trajectory will be reconstructed from the data. The aerodynamic parameters that will be reconstructed will be the axial force coefficient, freestream Mach number, base pressure, atmospheric density, and winds. The aerothermal quantities that will be determined are the heatshield and backshell aero-heating, turbulence transition across the heatshield, and TPS in-depth performance of PICA. By directly measuring the radiative and total heat fluxes on the back-shell, the convective portion of the heat flux will be estimated. The status
Segmented assimilation theory and perinatal health disparities among women of Mexican descent.
Johnson, Michelle A; Marchi, Kristen S
2009-07-01
A higher prevalence of infant low birth weight (Mexican descent living in the U.S. when compared to their less acculturated counterparts. Tests of the "acculturation hypothesis" have established that disparities in certain risks for low birth weight exist between subgroups of women of Mexican-origin. However, disparities observed by neighborhood of residence have yet to be explained. Most tests of the acculturation hypothesis assume a classical path of assimilation, whereby Mexican American health is expected to deteriorate with time spent residing in the U.S. and across the generations. The theory of segmented assimilation suggests that alternative paths are possible depending upon individual characteristics and the context of the neighborhood into which immigrant families and their children reside. This study tested the theory of segmented assimilation as a framework for examining the geographic, cultural, and socioeconomic underpinnings of population differences in infant low birth weight among women of Mexican descent in California using the 2000 U.S. Census and population-based data from the Maternal and Infant Health Assessment (1999-2005) (n=6442). Little support was found for the theory's hypotheses. Rather, increased odds for infant low birth weight were observed for English speakers residing in Latino immigrant neighborhoods when compared to English speakers in other neighborhoods, an effect attenuated for Spanish speakers. Elevated odds of low birth weight were also observed among English speakers residing in Latino immigrant neighborhoods when compared to Spanish speakers in the same neighborhoods. Findings suggest the transfer of health-specific social capital in ethnic neighborhoods may depend upon sociocultural consonance between individuals and neighborhood residents. The authors call for additional research that sheds light on the sociocultural dynamics of maternal and infant health at multiple levels.
Genetic Heterogeneity in Colorectal Cancer Associations in Americans of African vs. European Descent
Kupfer, Sonia S.; Anderson, Jeffrey R.; Hooker, Stanley; Skol, Andrew; Kittles, Rick A.; Keku, Temitope O.; Sandler, Robert S.; Ellis, Nathan A.
2013-01-01
Background & Aims Genome-wide association studies of colorectal cancer (CRC) have identified risk variants in 10 genomic regions. None of these studies included African Americans, who have the highest incidence and mortality from CRC in the US. For the 10 genomic regions, we performed an association study of Americans of African and European descent. Methods We genotyped 22 single nucleotide polymorphisms (SNPs) in DNA samples from 1194 patients with CRC (795 African Americans and 399 European Americans) and 1352 controls (985 African Americans and 367 European Americans). At chromosome 8q24.21 region 3, we analyzed 6 SNPs from 1000 African American cases and 1393 controls. Association testing was done using multivariate logistic regression controlling for ancestry, age, and sex. Results Sizes and directions of association for all SNPs tested in European Americans were consistent with previously published studies, but for 9 of 22 SNPs tested in African Americans, they were of an opposite direction. Among African Americans, the SNP rs6983267 at 8q24.21 was not associated with CRC (odds ratio [OR]=1.18; P=0.12); instead, the 8q24.21 SNP rs7014346 (OR=1.15; p=0.03) was associated with CRC in this population. At 15q13.3, rs10318 was associated with CRC in both populations. At 10p14, the opposite allele of rs10795668 was associated with CRC in African Americans (OR=1.35; P=0.04). At 11q23.1, rs3802842 was significantly associated with rectal cancer risk only among African Americans (OR 1.34; P=0.01); this observation was made in previous studies. Among European Americans, SNPs at 8q24.21, 11q23.1, and 16q22.1 were associated with CRC, in agreement with previous reports. Conclusion There is genetic heterogeneity in CRC associations in Americans of African vs. European descent. PMID:20659471
The effects of the diurnal atmospheric variability on entry, descent and landing on Mars
Directory of Open Access Journals (Sweden)
Marčeta D.
2014-01-01
Full Text Available Landing on Mars is extremely challenging task due to the fact that the Martian atmosphere is the most hostile environment in the Solar system to perform the entry, descent and landing (EDL process, because it is thick enough to create substantial heating of the entry vehicle but not thick enough to reduce its velocity to the one necessary for safe landing. Beside this, the atmosphere is very dynamic mainly due to high eccentricity of the Martian orbit, obliquity of the orbital to the equatorial plane and close alignment of the winter solstice and the orbital perihelion. Although seasonal variations of atmospheric parameters are significantly larger than the diurnal, it is very important to analyze diurnal cycles as they can significantly change vertical and horizontal atmospheric profiles in very short time intervals. This can present a serious threat to missions which have very precise timings and specific requirements such as the requirement for the daytime landing to enable ground images acquisition during the descent and landing phase. A 3-degrees-of-freedom trajectory integration routine was combined with the Mars Global Reference Atmospheric Model (Mars-GRAM to identify the dependence of the EDL profiles on the diurnal cycles of atmospheric parameters throughout the Martian year. The obtained results show that the influence of the diurnal cycles is the largest at the equator and decreases relatively symmetrically towards the poles with a slightly stronger influence in the northern hemisphere. Also, there is a significant influence of the orbital position of Mars on the effect of diurnal atmospheric variations which causes that, around the orbital perihelion and winter solstice, there is some kind of inversion of the dependance of optimal entry timing on latitude of the landing site comparing to the rest of the Martian year. [Projekat Ministarstva nauke Republike Srbije, br. 176002
Elemental gradients in macrophytes from a reactor effluent gradient
International Nuclear Information System (INIS)
Grace, J.B.; Tilly, L.J.
1978-01-01
The tissues of submersed macrophtes from along the thermal gradient were analyzed for phosphorus to determine whether any pattern correspondent to standing crop distributions could be detected. Although water concentrations of phosphorus showed no detectable relationship to the thermal effluent, tissue concentrations of this element in submersed macrophytes declined with distance from the effluent entry point. The occurrence of this concentration pattern suggests that phosphorus availability is greater near the discharge. Because phosphorus is the element most often determined to limit aquatic productivity, its greater availability may partially account for the apparent enhancement of macrophte growth near the thermal discharge. A patter of macrophyte abundance which indicated enchancement related to the discharge gradient in the reactor-cooling reservoir, Par Pond is reported. Correlative data tended to implicate light and temperature as important in influencing the differential abundance pattern
Q-deformed systems and constrained dynamics
International Nuclear Information System (INIS)
Shabanov, S.V.
1993-01-01
It is shown that quantum theories of the q-deformed harmonic oscillator and one-dimensional free q-particle (a free particle on the 'quantum' line) can be obtained by the canonical quantization of classical Hamiltonian systems with commutative phase-space variables and a non-trivial symplectic structure. In the framework of this approach, classical dynamics of a particle on the q-line coincides with the one of a free particle with friction. It is argued that q-deformed systems can be treated as ordinary mechanical systems with the second-class constraints. In particular, second-class constrained systems corresponding to the q-oscillator and q-particle are given. A possibility of formulating q-deformed systems via gauge theories (first-class constrained systems) is briefly discussed. (orig.)
Cosmogenic photons strongly constrain UHECR source models
Directory of Open Access Journals (Sweden)
van Vliet Arjen
2017-01-01
Full Text Available With the newest version of our Monte Carlo code for ultra-high-energy cosmic ray (UHECR propagation, CRPropa 3, the flux of neutrinos and photons due to interactions of UHECRs with extragalactic background light can be predicted. Together with the recently updated data for the isotropic diffuse gamma-ray background (IGRB by Fermi LAT, it is now possible to severely constrain UHECR source models. The evolution of the UHECR sources especially plays an important role in the determination of the expected secondary photon spectrum. Pure proton UHECR models are already strongly constrained, primarily by the highest energy bins of Fermi LAT’s IGRB, as long as their number density is not strongly peaked at recent times.
An autonomous vehicle: Constrained test and evaluation
Griswold, Norman C.
1991-11-01
The objective of the research is to develop an autonomous vehicle which utilizes stereo camera sensors (using ambient light) to follow complex paths at speeds up to 35 mph with consideration of moving vehicles within the path. The task is intended to demonstrate the contribution to safety of a vehicle under automatic control. All of the long-term scenarios investigating future reduction in congestion involve an automatic system taking control, or partial control, of the vehicle. A vehicle which includes a collision avoidance system is a prerequisite to an automatic control system. The report outlines the results of a constrained test of a vision controlled vehicle. In order to demonstrate its ability to perform on the current street system the vehicle was constrained to recognize, approach, and stop at an ordinary roadside stop sign.
Doubly Constrained Robust Blind Beamforming Algorithm
Directory of Open Access Journals (Sweden)
Xin Song
2013-01-01
Full Text Available We propose doubly constrained robust least-squares constant modulus algorithm (LSCMA to solve the problem of signal steering vector mismatches via the Bayesian method and worst-case performance optimization, which is based on the mismatches between the actual and presumed steering vectors. The weight vector is iteratively updated with penalty for the worst-case signal steering vector by the partial Taylor-series expansion and Lagrange multiplier method, in which the Lagrange multipliers can be optimally derived and incorporated at each step. A theoretical analysis for our proposed algorithm in terms of complexity cost, convergence performance, and SINR performance is presented in this paper. In contrast to the linearly constrained LSCMA, the proposed algorithm provides better robustness against the signal steering vector mismatches, yields higher signal captive performance, improves greater array output SINR, and has a lower computational cost. The simulation results confirm the superiority of the proposed algorithm on beampattern control and output SINR enhancement.
Coding for Two Dimensional Constrained Fields
DEFF Research Database (Denmark)
Laursen, Torben Vaarbye
2006-01-01
a first order model to model higher order constraints by the use of an alphabet extension. We present an iterative method that based on a set of conditional probabilities can help in choosing the large numbers of parameters of the model in order to obtain a stationary model. Explicit results are given...... for the No Isolated Bits constraint. Finally we present a variation of the encoding scheme of bit-stuffing that is applicable to the class of checkerboard constrained fields. It is possible to calculate the entropy of the coding scheme thus obtaining lower bounds on the entropy of the fields considered. These lower...... bounds are very tight for the Run-Length limited fields. Explicit bounds are given for the diamond constrained field as well....
Y. Güzelcan (Yener); P. van Loon (Peter)
2009-01-01
textabstractBackground: Studies have shown a clear relationship between depressive disorders and vitamin B12 deficiency. Gastroenteritis and Helicobacter pylori infections can cause vitamin B12 deficiency. Helicobacter pylori infections are not uncommon among people of Turkish descent in The
Utsey, Shawn O.; Brown, Christa; Bolden, Mark A.
2004-01-01
Confirmatory factor analysis was used to test the factorial invariance of the Africultural Coping Systems Inventory's (ACSI) measurement model and underlying factor structure across three independent and ethnically distinct samples of African descent populations. Results indicated that factor pattern coefficients of the ACSI's underlying…
Directory of Open Access Journals (Sweden)
McQuillan Ruth
2010-02-01
Full Text Available Abstract Background Genome-wide homozygosity estimation from genomic data is becoming an increasingly interesting research topic. The aim of this study was to compare different methods for estimating individual homozygosity-by-descent based on the information from human genome-wide scans rather than genealogies. We considered the four most commonly used methods and investigated their applicability to single-nucleotide polymorphism (SNP data in both a simulation study and by using the human genotyped data. A total of 986 inhabitants from the isolated Island of Vis, Croatia (where inbreeding is present, but no pedigree-based inbreeding was observed at the level of F > 0.0625 were included in this study. All individuals were genotyped with the Illumina HumanHap300 array with 317,503 SNP markers. Results Simulation data suggested that multi-point FEstim is the method most strongly correlated to true homozygosity-by-descent. Correlation coefficients between the homozygosity-by-descent estimates were high but only for inbred individuals, with nearly absolute correlation between single-point measures. Conclusions Deciding who is really inbred is a methodological challenge where multi-point approaches can be very helpful once the set of SNP markers is filtered to remove linkage disequilibrium. The use of several different methodological approaches and hence different homozygosity measures can help to distinguish between homozygosity-by-state and homozygosity-by-descent in studies investigating the effects of genomic autozygosity on human health.
Crowell, Candice N; Delgado-Romero, Edward A; Mosley, Della V; Huynh, Sophia
2016-08-01
Research on Black sexual health often fails to represent the heterogeneity of Black ethnic groups. For people of Caribbean descent in the USA, ethnicity is a salient cultural factor that influences definitions and experiences of sexual health. Most research on people of Caribbean descent focuses on the relatively high rate of STIs, but sexual health is defined more broadly than STI prevalence. Psychological and emotional indicators and the voice of participants are important to consider when exploring the sexual health of a minority culture. The purpose of this study was to qualitatively explore how heterosexual Black men of Caribbean descent define and understand sexual health for themselves. Eleven men who self-identified as Black, Caribbean and heterosexual participated in three focus groups and were asked to define sexual health, critique behaviours expertly identified as healthy and address what encourages and discourages sexual health in their lives. Findings point to six dimensions of sexual health for heterosexual Black men of Caribbean descent. These include: heterosexually privileged, protective, contextual, interpersonal, cultural and pleasurable dimensions. There were some notable departures from current expert definitions of sexual health. Recommendations for further theory development are provided.
Severe G6PD Deficiency Due to a New Missense Mutation in an Infant of Northern European Descent
DEFF Research Database (Denmark)
Warny, Marie; Lausen, Birgitte; Birgens, Henrik
2015-01-01
We report a term male infant born to parents of Danish descent, who on the second day of life developed jaundice peaking at 67 hours and decreasing on applied double-sided phototherapy. In the weeks following, the infant showed signs of ongoing hemolysis. Laboratory tests showed very low glucose-6...
Kamassah, Sharon
2010-01-01
This research study focused on the factors that enable women of South Asian and African descent to succeed as leaders in the college system. The findings were derived from online questionnaires and in-depth interviews of 16 racialized women from two Greater Toronto Area (GTA) colleges. Many factors and recommendations were shared. Some of the…
Pease-Alvarez, Lucinda
A study investigated patterns and influences in Mexican-American children's Spanish language maintenance and shift toward English dominance or monolingualism. Subjects were 64 Mexican-descent children, ages 8-9, of varying immigration backgrounds (Mexican-born, U.S.-born of Mexican-born parents, U.S.-born of U.S.-born parents), and their families…
Meinema, Jennita G.; van Dijk, Nynke; Beune, Erik J. A. J.; Jaarsma, Debbie A. D. C.; van Weert, Henk C. P. M.; Haafkens, Joke A.
2015-01-01
In Western countries, better knowledge about patient-related determinants of treatment adherence (medication and lifestyle) is needed to improve treatment adherence and outcomes among hypertensive ethnic minority patients of African descent. To identify patient-related determinants of adherence to
Conchas, Gilberto Q.; Vigil, James Diego
2010-01-01
This article conceptualizes the crucial social and developmental features impacting Mexican-descent youth and adolescents in low-income communities in southern California. All youth in these neighborhoods must confront and come to grips with the many environmental, socioeconomic, racial, and cultural forces they confront. However, it is the…
Sasaki, Lindsey
2012-01-01
International migration between Japan and Brazil dates back to 1908, when the first group of Japanese migrated to Brazil. However, in the 1980s, a reverse flow occurred, as thousands of Brazilians of Japanese descent traveled to Japan to work in manufacturing and construction factories ("dekasegi" workers). Japanese Brazilians up until…
Experimental studies of the rotor flow downwash on the Stability of multi-rotor crafts in descent
Veismann, Marcel; Dougherty, Christopher; Gharib, Morteza
2017-11-01
All rotorcrafts, including helicopters and multicopters, have the inherent problem of entering rotor downwash during vertical descent. As a result, the craft is subject to highly unsteady flow, called vortex ring state (VRS), which leads to a loss of lift and reduced stability. To date, experimental efforts to investigate this phenomenon have been largely limited to analysis of a single, fixed rotor mounted in a horizontal wind tunnel. Our current work aims to understand the interaction of multiple rotors in vertical descent by mounting a multi-rotor craft in a low speed, vertical wind tunnel. Experiments were performed with a fixed and rotationally free mounting; the latter allowing us to better capture the dynamics of a free flying drone. The effect of rotor separation on stability, generated thrust, and rotor wake interaction was characterized using force gauge data and PIV analysis for various descent velocities. The results obtained help us better understand fluid-craft interactions of drones in vertical descent and identify possible sources of instability. The presented material is based upon work supported by the Center for Autonomous Systems and Technologies (CAST) at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT).
Constraining supergravity models from gluino production
International Nuclear Information System (INIS)
Barbieri, R.; Gamberini, G.; Giudice, G.F.; Ridolfi, G.
1988-01-01
The branching ratios for gluino decays g tilde → qanti qΧ, g tilde → gΧ into a stable undetected neutralino are computed as functions of the relevant parameters of the underlying supergravity theory. A simple way of constraining supergravity models from gluino production emerges. The effectiveness of hadronic versus e + e - colliders in the search for supersymmetry can be directly compared. (orig.)
Chance Constrained Optimization for Targeted Internet Advertising
Deza, Antoine; Huang, Kai; Metel, Michael R.
2014-01-01
We introduce a chance constrained optimization model for the fulfillment of guaranteed display Internet advertising campaigns. The proposed formulation for the allocation of display inventory takes into account the uncertainty of the supply of Internet viewers. We discuss and present theoretical and computational features of the model via Monte Carlo sampling and convex approximations. Theoretical upper and lower bounds are presented along with a numerical substantiation.
An English language interface for constrained domains
Page, Brenda J.
1989-01-01
The Multi-Satellite Operations Control Center (MSOCC) Jargon Interpreter (MJI) demonstrates an English language interface for a constrained domain. A constrained domain is defined as one with a small and well delineated set of actions and objects. The set of actions chosen for the MJI is from the domain of MSOCC Applications Executive (MAE) Systems Test and Operations Language (STOL) directives and contains directives for signing a cathode ray tube (CRT) on or off, calling up or clearing a display page, starting or stopping a procedure, and controlling history recording. The set of objects chosen consists of CRTs, display pages, STOL procedures, and history files. Translation from English sentences to STOL directives is done in two phases. In the first phase, an augmented transition net (ATN) parser and dictionary are used for determining grammatically correct parsings of input sentences. In the second phase, grammatically typed sentences are submitted to a forward-chaining rule-based system for interpretation and translation into equivalent MAE STOL directives. Tests of the MJI show that it is able to translate individual clearly stated sentences into the subset of directives selected for the prototype. This approach to an English language interface may be used for similarly constrained situations by modifying the MJI's dictionary and rules to reflect the change of domain.
An Introduction to the Conjugate Gradient Method that Even an Idiot Can Understand
1994-03-07
vectors are orthogonal. Steepest Descent. To see this, set the directional derivative to zero: d f --df(x(i+[)) = 0 Td T -ri~~dj)= 0 dT Ae(i+ 1) = 0...From Equation 40, d Td (i)r(i) -- uTr(i). (42) 28 Jonathan Richard Shewchuk ’(2) d(2 e(2) Figure 27: In the method of Conjugate Gradients, each new...Equation 38: rTi)r(j+l) =r( iyr (j) -- o(j)r T)Ad~j T T a(j)r(i)Ad(j) = r(i)r(j) - r(i)r(j+I) SI rT T) ( ) r(i), = ,T ! rT r(i)Ad(j) = -,T,_ r(i)r(i), i
Vertebrate pressure-gradient receivers
DEFF Research Database (Denmark)
Christensen-Dalsgaard, Jakob
2011-01-01
The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum and stro......The eardrums of all terrestrial vertebrates (tetrapods) are connected through Eustachian tubes or interaural canals. In some of the animals, these connections create pressure-gradient directionality, an enhanced directionality by interaction of sound arriving at both sides of the eardrum....... Recent vertebrates form a continuum from perfect interaural transmission (0 dB in a certain frequency band) and pronounced eardrum directionality (30-40 dB) in the lizards, over somewhat attenuated transmission and limited directionality in birds and frogs, to the strongly attenuated interaural...
A hybrid guided neighborhood search for the disjunctively constrained knapsack problem
Directory of Open Access Journals (Sweden)
Mhand Hifi
2015-12-01
Full Text Available In this paper, we investigate the use of a hybrid guided neighborhood search for solving the disjunctively constrained knapsack problem. The studied problem may be viewed as a combination of two NP-hard combinatorial optimization problems: the weighted-independent set and the classical binary knapsack. The proposed algorithm is a hybrid approach that combines both deterministic and random local searches. The deterministic local search is based on a descent method, where both building and exploring procedures are alternatively used for improving the solution at hand. In order to escape from a local optima, a random local search strategy is introduced which is based on a modified ant colony optimization system. During the search process, the ant colony optimization system tries to diversify and to enhance the solutions using some informations collected from the previous iterations. Finally, the proposed algorithm is computationally analyzed on a set of benchmark instances available in the literature. The provided results are compared to those realized by both the Cplex solver and a recent algorithm of the literature. The computational part shows that the obtained results improve most existing solution values.
Primordial vorticity and gradient expansion
Giovannini, Massimo
2012-01-01
The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $\\Lambda$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the or...
Bacterial Response to Antibiotic Gradients in a Porous Microfluidic Device
Deng, J.; Shechtman, L. A.; Sanford, R. A.; Dong, Y.; Werth, C. J.; Fouke, B. W.
2015-12-01
Microorganisms in nature have evolved survival strategies to cope with a wide variety of environmental stresses, including gradients in temperature, pH, substrate availability and aqueous chemistry. Microfluidic devices provide a consistently reliable real-time means to quantitatively measure, control and reproduce the dynamic nature of these stresses. As an example, accelerated adaptation from genetic mutations have been observed in E. coli as it responds to gradients of Ciprofloxacin (Zhang et. al. 2011). However, the mechanisms by which bacteria respond to antibiotic gradients, as well as the effect of changes in how the stressor is applied, have not been systematically studied. In this study, newly designed and fabricated microfluidic devices with porous media have been utilized to determine the chemical stress fields that enhance adaptation and thus to test how E. coli bacterial communities adapt to antibiotic stresses. By applying antibiotic and nutrient into inlet channels adjacent to either side of the porous media inoculated with E. coli, a gradient of antibiotic was formed. Hydrogel barriers were selectively photo-polymerized in between of the inlet channels and the porous media to prevent any undesired convection. Hence, chemical solute can only be transported by diffusion, creating a reproducible antibiotic gradient over the porous media. The bacteria were also constrained by the hydrogel boundary barriers from escaping the porous media. Preliminary results suggest that E. coli moves freely with respect to Ciprofloxacin concentrations. In addition, and unexpectedly, the E. coli colonies exhibit a concentric pulsed growth front radiating away from the point of inoculation within the micromodel ecosystem and pulse over the porous media containing antibiotic. The bacteria at the growth front grow into long filaments (up to 100μm) while the bacteria in the inner concentric area are normal size. We hypothesize that the frontier bacteria, which are first
21 CFR 888.3780 - Wrist joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Wrist joint polymer constrained prosthesis. 888.3780 Section 888.3780 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN... constrained prosthesis. (a) Identification. A wrist joint polymer constrained prosthesis is a device made of...
21 CFR 888.3230 - Finger joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Finger joint polymer constrained prosthesis. 888... constrained prosthesis. (a) Identification. A finger joint polymer constrained prosthesis is a device intended... generic type of device includes prostheses that consist of a single flexible across-the-joint component...
Cascading Constrained 2-D Arrays using Periodic Merging Arrays
DEFF Research Database (Denmark)
Forchhammer, Søren; Laursen, Torben Vaarby
2003-01-01
We consider a method for designing 2-D constrained codes by cascading finite width arrays using predefined finite width periodic merging arrays. This provides a constructive lower bound on the capacity of the 2-D constrained code. Examples include symmetric RLL and density constrained codes...
Spacecraft Trajectory Generation by Successive Approximation for Powered Descent and Cyclers
Casoliva, Jordi
Methods for spacecraft trajectory generation must be reliable. Complex nonlinear dynamics and constraints impede straightforward approaches. The approach pursued in this dissertation is to use successive approximation, which entails solving a sequence of problems, each one of which can be solved reliably, leading to the solution of the problem of interest. First, contractive sequential convex programming (CSCP) is developed and then applied to the problem of optimal powered descent landing in the presence of complex constraints, aerodynamic force and nonlinear engine performance. Second, numerical continuation is applied to the generation of cycler (periodic) spacecraft trajectories in the Earth-Moon system, the challenge here being the multiple scales of the three-body dynamics. The first-order necessary conditions for minimum-fuel powered descent are derived and interpreted. Both a point-mass model with throttle and thrust angle control and a rigid-body model with throttle and angular velocity control are considered, with a more complete analysis of the rigid-body case than previously available in the literature. The effects of boundary conditions on the thrust direction and finite bounds on the angular velocities are analyzed for the rigid-body case. Minimum-fuel solutions, obtained numerically, illustrate the optimal strategies. The optimal powered descent landing problem considered in the development of CSCP has a convex cost function, nonlinear dynamics, convex state constraints and nonlinear non-convex control constraints. The non-convexity in the control constraints is handled with the lossless convexification technique which consists of a convex relaxation on the control constraints. The novelty of CSCP is the ability to account for nonlinear dynamics and nonlinear control bounds in the optimal control problem and the use of interior-point methods for second-order cone programs which are guaranteed to find the optimal solution. CSCP solves a convergent
Instabilities in power law gradient hardening materials
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Tvergaard, Viggo
2005-01-01
Tension and compression instabilities are investigated for specimens with dimensions in the micron range. A finite strain generalization of a higher order strain gradient plasticity theory is implemented in a finite element scheme capable of modeling power law hardening materials. Effects...... of gradient hardening are found to delay the onset of localization under plane strain tension, and significantly reduce strain gradients in the localized zone. For plane strain compression gradient hardening is found to increase the load-carrying capacity significantly....
Kuwata, Yoshiaki; Pavone, Marco; Balaram, J. (Bob)
2012-01-01
This paper presents a novel risk-constrained multi-stage decision making approach to the architectural analysis of planetary rover missions. In particular, focusing on a 2018 Mars rover concept, which was considered as part of a potential Mars Sample Return campaign, we model the entry, descent, and landing (EDL) phase and the rover traverse phase as four sequential decision-making stages. The problem is to find a sequence of divert and driving maneuvers so that the rover drive is minimized and the probability of a mission failure (e.g., due to a failed landing) is below a user specified bound. By solving this problem for several different values of the model parameters (e.g., divert authority), this approach enables rigorous, accurate and systematic trade-offs for the EDL system vs. the mobility system, and, more in general, cross-domain trade-offs for the different phases of a space mission. The overall optimization problem can be seen as a chance-constrained dynamic programming problem, with the additional complexity that 1) in some stages the disturbances do not have any probabilistic characterization, and 2) the state space is extremely large (i.e, hundreds of millions of states for trade-offs with high-resolution Martian maps). To this purpose, we solve the problem by performing an unconventional combination of average and minimax cost analysis and by leveraging high efficient computation tools from the image processing community. Preliminary trade-off results are presented.
Gradient remediability in linear distributed parabolic systems ...
African Journals Online (AJOL)
The aim of this paper is the introduction of a new concept that concerned the analysis of a large class of distributed parabolic systems. It is the general concept of gradient remediability. More precisely, we study with respect to the gradient observation, the existence of an input operator (gradient efficient actuators) ensuring ...
Estimation of gradients from scattered data
Energy Technology Data Exchange (ETDEWEB)
Stead, S.E.
1984-01-01
Many techniques for producing a surface from scattered data require gradients at the data points. Since only positional data are usually known, the gradients must be estimated before the surface can be computed. The quality of the surface depends on the estimated gradients; so it is important to compute accurate estimates.
Energy Technology Data Exchange (ETDEWEB)
Tung, Wu-Hsiung, E-mail: wstong@iner.gov.tw; Lee, Tien-Tso; Kuo, Weng-Sheng; Yaur, Shung-Jung
2017-03-15
Highlights: • An optimization method for axial enrichment distribution in a BWR fuel was developed. • Block coordinate descent method is employed to search for optimal solution. • Scoping libraries are used to reduce computational effort. • Optimization search space consists of enrichment difference parameters. • Capability of the method to find optimal solution is demonstrated. - Abstract: An optimization method has been developed to search for the optimal axial enrichment distribution in a fuel assembly for a boiling water reactor core. The optimization method features: (1) employing the block coordinate descent method to find the optimal solution in the space of enrichment difference parameters, (2) using scoping libraries to reduce the amount of CASMO-4 calculation, and (3) integrating a core critical constraint into the objective function that is used to quantify the quality of an axial enrichment design. The objective function consists of the weighted sum of core parameters such as shutdown margin and critical power ratio. The core parameters are evaluated by using SIMULATE-3, and the cross section data required for the SIMULATE-3 calculation are generated by using CASMO-4 and scoping libraries. The application of the method to a 4-segment fuel design (with the highest allowable segment enrichment relaxed to 5%) demonstrated that the method can obtain an axial enrichment design with improved thermal limit ratios and objective function value while satisfying the core design constraints and core critical requirement through the use of an objective function. The use of scoping libraries effectively reduced the number of CASMO-4 calculation, from 85 to 24, in the 4-segment optimization case. An exhausted search was performed to examine the capability of the method in finding the optimal solution for a 4-segment fuel design. The results show that the method found a solution very close to the optimum obtained by the exhausted search. The number of
An education gradient in health, a health gradient in education, or a confounded gradient in both?
Lynch, Jamie L; von Hippel, Paul T
2016-04-01
There is a positive gradient associating educational attainment with health, yet the explanation for this gradient is not clear. Does higher education improve health (causation)? Do the healthy become highly educated (selection)? Or do good health and high educational attainment both result from advantages established early in the life course (confounding)? This study evaluates these competing explanations by tracking changes in educational attainment and Self-rated Health (SRH) from age 15 to age 31 in the National Longitudinal Study of Youth, 1997 cohort. Ordinal logistic regression confirms that high-SRH adolescents are more likely to become highly educated. This is partly because adolescent SRH is associated with early advantages including adolescents' academic performance, college plans, and family background (confounding); however, net of these confounders adolescent SRH still predicts adult educational attainment (selection). Fixed-effects longitudinal regression shows that educational attainment has little causal effect on SRH at age 31. Completion of a high school diploma or associate's degree has no effect on SRH, while completion of a bachelor's or graduate degree have effects that, though significant, are quite small (less than 0.1 points on a 5-point scale). While it is possible that educational attainment would have greater effect on health at older ages, at age 31 what we see is a health gradient in education, shaped primarily by selection and confounding rather than by a causal effect of education on health. Copyright © 2016 Elsevier Ltd. All rights reserved.
On Tree-Constrained Matchings and Generalizations
Canzar, Stefan; Elbassioni, Khaled; Klau, Gunnar W.; Mestre, Julián
2015-01-01
htmlabstractWe consider the following \\textsc{Tree-Constrained Bipartite Matching} problem: Given two rooted trees $T_1=(V_1,E_1)$, $T_2=(V_2,E_2)$ and a weight function $w: V_1\\times V_2 \\mapsto \\mathbb{R}_+$, find a maximum weight matching $\\mathcal{M}$ between nodes of the two trees, such that none of the matched nodes is an ancestor of another matched node in either of the trees. This generalization of the classical bipartite matching problem appears, for example, in the computational ana...
Quantization of soluble classical constrained systems
International Nuclear Information System (INIS)
Belhadi, Z.; Menas, F.; Bérard, A.; Mohrbach, H.
2014-01-01
The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way
Quantization of soluble classical constrained systems
Energy Technology Data Exchange (ETDEWEB)
Belhadi, Z. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Laboratoire de physique théorique, Faculté des sciences exactes, Université de Bejaia, 06000 Bejaia (Algeria); Menas, F. [Laboratoire de physique et chimie quantique, Faculté des sciences, Université Mouloud Mammeri, BP 17, 15000 Tizi Ouzou (Algeria); Ecole Nationale Préparatoire aux Etudes d’ingéniorat, Laboratoire de physique, RN 5 Rouiba, Alger (Algeria); Bérard, A. [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France); Mohrbach, H., E-mail: herve.mohrbach@univ-lorraine.fr [Equipe BioPhysStat, Laboratoire LCP-A2MC, ICPMB, IF CNRS No 2843, Université de Lorraine, 1 Bd Arago, 57078 Metz Cedex (France)
2014-12-15
The derivation of the brackets among coordinates and momenta for classical constrained systems is a necessary step toward their quantization. Here we present a new approach for the determination of the classical brackets which does neither require Dirac’s formalism nor the symplectic method of Faddeev and Jackiw. This approach is based on the computation of the brackets between the constants of integration of the exact solutions of the equations of motion. From them all brackets of the dynamical variables of the system can be deduced in a straightforward way.
Anomalous gauge theories as constrained Hamiltonian systems
International Nuclear Information System (INIS)
Fujiwara, T.
1989-01-01
Anomalous gauge theories considered as constrained systems are investigated. The effects of chiral anomaly on the canonical structure are examined first for nonlinear σ-model and later for fermionic theory. The breakdown of the Gauss law constraints and the anomalous commutators among them are studied in a systematic way. An intrinsic mass term for gauge fields makes it possible to solve the Gauss law relations as second class constraints. Dirac brackets between the time components of gauge fields are shown to involve anomalous terms. Based upon the Ward-Takahashi identities for gauge symmetry, we investigate anomalous fermionic theory within the framework of path integral approach. (orig.)
Communication Schemes with Constrained Reordering of Resources
DEFF Research Database (Denmark)
Popovski, Petar; Utkovski, Zoran; Trillingsgaard, Kasper Fløe
2013-01-01
reordering of the labelled user resources (packets, channels) in an existing, primary system. However, the degrees of freedom of the reordering are constrained by the operation of the primary system. The second scenario is related to communication systems with energy harvesting, where the transmitted signals...... pertaining to the communication model when the resources that can be reordered have binary values. The capacity result is valid under arbitrary error model in which errors in each resource (packet) occur independently. Inspired by the information—theoretic analysis, we have shown how to design practical...
Can Neutron stars constrain Dark Matter?
DEFF Research Database (Denmark)
Kouvaris, Christoforos; Tinyakov, Peter
2010-01-01
We argue that observations of old neutron stars can impose constraints on dark matter candidates even with very small elastic or inelastic cross section, and self-annihilation cross section. We find that old neutron stars close to the galactic center or in globular clusters can maintain a surface...... temperature that could in principle be detected. Due to their compactness, neutron stars can acrete WIMPs efficiently even if the WIMP-to-nucleon cross section obeys the current limits from direct dark matter searches, and therefore they could constrain a wide range of dark matter candidates....
Shape reconstruction from gradient data.
Ettl, Svenja; Kaminski, Jürgen; Knauer, Markus C; Häusler, Gerd
2008-04-20
We present a generalized method for reconstructing the shape of an object from measured gradient data. A certain class of optical sensors does not measure the shape of an object but rather its local slope. These sensors display several advantages, including high information efficiency, sensitivity, and robustness. For many applications, however, it is necessary to acquire the shape, which must be calculated from the slopes by numerical integration. Existing integration techniques show drawbacks that render them unusable in many cases. Our method is based on an approximation employing radial basis functions. It can be applied to irregularly sampled, noisy, and incomplete data, and it reconstructs surfaces both locally and globally with high accuracy.
Temperature Gradient in Hall Thrusters
International Nuclear Information System (INIS)
Staack, D.; Raitses, Y.; Fisch, N.J.
2003-01-01
Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons
Stringy bounces and gradient instabilities
Giovannini, Massimo
2017-01-01
Bouncing solutions are obtained from a generally covariant action characterized by a potential which is a nonlocal functional of the dilaton field at two separated space-time points. Gradient instabilities are shown to arise in this context but they are argued to be nongeneric. After performing a gauge-invariant and frame-invariant derivation of the evolution equations of the fluctuations, a heuristic criterium for the avoidance of pathological instabilities is proposed and corroborated by a number of explicit examples that turn out to be compatible with a quasi-flat spectrum of curvature inhomogeneities for typical wavelengths larger than the Hubble radius.
Generalized Gradient Approximation Made Simple
International Nuclear Information System (INIS)
Perdew, J.P.; Burke, K.; Ernzerhof, M.
1996-01-01
Generalized gradient approximations (GGA close-quote s) for the exchange-correlation energy improve upon the local spin density (LSD) description of atoms, molecules, and solids. We present a simple derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental constants. Only general features of the detailed construction underlying the Perdew-Wang 1991 (PW91) GGA are invoked. Improvements over PW91 include an accurate description of the linear response of the uniform electron gas, correct behavior under uniform scaling, and a smoother potential. copyright 1996 The American Physical Society
Wang, Yang; Ma, Guowei; Ren, Feng; Li, Tuo
2017-12-01
A constrained Delaunay discretization method is developed to generate high-quality doubly adaptive meshes of highly discontinuous geological media. Complex features such as three-dimensional discrete fracture networks (DFNs), tunnels, shafts, slopes, boreholes, water curtains, and drainage systems are taken into account in the mesh generation. The constrained Delaunay triangulation method is used to create adaptive triangular elements on planar fractures. Persson's algorithm (Persson, 2005), based on an analogy between triangular elements and spring networks, is enriched to automatically discretize a planar fracture into mesh points with varying density and smooth-quality gradient. The triangulated planar fractures are treated as planar straight-line graphs (PSLGs) to construct piecewise-linear complex (PLC) for constrained Delaunay tetrahedralization. This guarantees the doubly adaptive characteristic of the resulted mesh: the mesh is adaptive not only along fractures but also in space. The quality of elements is compared with the results from an existing method. It is verified that the present method can generate smoother elements and a better distribution of element aspect ratios. Two numerical simulations are implemented to demonstrate that the present method can be applied to various simulations of complex geological media that contain a large number of discontinuities.
Little, Alan; Bose, Deepak; Karlgaard, Chris; Munk, Michelle; Kuhl, Chris; Schoenenberger, Mark; Antill, Chuck; Verhappen, Ron; Kutty, Prasad; White, Todd
2013-01-01
The Mars Science Laboratory (MSL) Entry, Descent and Landing Instrumentation (MEDLI) hardware was a first-of-its-kind sensor system that gathered temperature and pressure readings on the MSL heatshield during Mars entry on August 6, 2012. MEDLI began as challenging instrumentation problem, and has been a model of collaboration across multiple NASA organizations. After the culmination of almost 6 years of effort, the sensors performed extremely well, collecting data from before atmospheric interface through parachute deploy. This paper will summarize the history of the MEDLI project and hardware development, including key lessons learned that can apply to future instrumentation efforts. MEDLI returned an unprecedented amount of high-quality engineering data from a Mars entry vehicle. We will present the performance of the 3 sensor types: pressure, temperature, and isotherm tracking, as well as the performance of the custom-built sensor support electronics. A key component throughout the MEDLI project has been the ground testing and analysis effort required to understand the returned flight data. Although data analysis is ongoing through 2013, this paper will reveal some of the early findings on the aerothermodynamic environment that MSL encountered at Mars, the response of the heatshield material to that heating environment, and the aerodynamic performance of the entry vehicle. The MEDLI data results promise to challenge our engineering assumptions and revolutionize the way we account for margins in entry vehicle design.
Guidance and Control Algorithms for the Mars Entry, Descent and Landing Systems Analysis
Davis, Jody L.; CwyerCianciolo, Alicia M.; Powell, Richard W.; Shidner, Jeremy D.; Garcia-Llama, Eduardo
2010-01-01
The purpose of the Mars Entry, Descent and Landing Systems Analysis (EDL-SA) study was to identify feasible technologies that will enable human exploration of Mars, specifically to deliver large payloads to the Martian surface. This paper focuses on the methods used to guide and control two of the contending technologies, a mid- lift-to-drag (L/D) rigid aeroshell and a hypersonic inflatable aerodynamic decelerator (HIAD), through the entry portion of the trajectory. The Program to Optimize Simulated Trajectories II (POST2) is used to simulate and analyze the trajectories of the contending technologies and guidance and control algorithms. Three guidance algorithms are discussed in this paper: EDL theoretical guidance, Numerical Predictor-Corrector (NPC) guidance and Analytical Predictor-Corrector (APC) guidance. EDL-SA also considered two forms of control: bank angle control, similar to that used by Apollo and the Space Shuttle, and a center-of-gravity (CG) offset control. This paper presents the performance comparison of these guidance algorithms and summarizes the results as they impact the technology recommendations for future study.
Exploring the 3D Surfaces with Modified Method of Steepest Descent
Directory of Open Access Journals (Sweden)
Wioletta GRZENDA
2012-06-01
Full Text Available Aim: To prove expediency of the steepest descent method to divide a given cloud of (Y, X1, X2 points into the spatial clusters with purpose to estimate a simple regression model Y = f(Z|X1,X2 at each cluster. Material and Method: The exemplary data sets {Y, X1, X2} were drawn randomly from assumed 3D surface: Y = f(X1,X2, and then a random noise was added to variable Y. A polynomial model Y = f(X1,X2 and a set of models Y = f(Z|X1,X2 were estimated separately, both under Akaike information criterion (AIC, and then compared with respect to their determination coefficients R-square, and the residuals’ distributions. Results: In the artificial data set studied, the both compared methods after several iterations can provide regression models of the quite similar quality. Conclusions: Because the proposed novel method seems to be more robust to outliers, and easier to graphical presentations and to intuitive understanding than the conventional way of building a regression model, the proposed novel method can be recommended to use by non-statisticians, especially in situation when, besides usual moderate noise, the sporadic but influential measurement errors can occur.
Two-way regularization for MEG source reconstruction via multilevel coordinate descent
Siva Tian, Tian
2013-12-01
Magnetoencephalography (MEG) source reconstruction refers to the inverse problem of recovering the neural activity from the MEG time course measurements. A spatiotemporal two-way regularization (TWR) method was recently proposed by Tian et al. to solve this inverse problem and was shown to outperform several one-way regularization methods and spatiotemporal methods. This TWR method is a two-stage procedure that first obtains a raw estimate of the source signals and then refines the raw estimate to ensure spatial focality and temporal smoothness using spatiotemporal regularized matrix decomposition. Although proven to be effective, the performance of two-stage TWR depends on the quality of the raw estimate. In this paper we directly solve the MEG source reconstruction problem using a multivariate penalized regression where the number of variables is much larger than the number of cases. A special feature of this regression is that the regression coefficient matrix has a spatiotemporal two-way structure that naturally invites a two-way penalty. Making use of this structure, we develop a computationally efficient multilevel coordinate descent algorithm to implement the method. This new one-stage TWR method has shown its superiority to the two-stage TWR method in three simulation studies with different levels of complexity and a real-world MEG data analysis. © 2013 Wiley Periodicals, Inc., A Wiley Company.
Direct-to-Earth Communications with Mars Science Laboratory During Entry, Descent, and Landing
Soriano, Melissa; Finley, Susan; Fort, David; Schratz, Brian; Ilott, Peter; Mukai, Ryan; Estabrook, Polly; Oudrhiri, Kamal; Kahan, Daniel; Satorius, Edgar
2013-01-01
Mars Science Laboratory (MSL) undergoes extreme heating and acceleration during Entry, Descent, and Landing (EDL) on Mars. Unknown dynamics lead to large Doppler shifts, making communication challenging. During EDL, a special form of Multiple Frequency Shift Keying (MFSK) communication is used for Direct-To-Earth (DTE) communication. The X-band signal is received by the Deep Space Network (DSN) at the Canberra Deep Space Communication complex, then down-converted, digitized, and recorded by open-loop Radio Science Receivers (RSR), and decoded in real-time by the EDL Data Analysis (EDA) System. The EDA uses lock states with configurable Fast Fourier Transforms to acquire and track the signal. RSR configuration and channel allocation is shown. Testing prior to EDL is discussed including software simulations, test bed runs with MSL flight hardware, and the in-flight end-to-end test. EDA configuration parameters and signal dynamics during pre-entry, entry, and parachute deployment are analyzed. RSR and EDA performance during MSL EDL is evaluated, including performance using a single 70-meter DSN antenna and an array of two 34-meter DSN antennas as a back up to the 70-meter antenna.
Parente2: a fast and accurate method for detecting identity by descent
Rodriguez, Jesse M.
2014-10-01
Identity-by-descent (IBD) inference is the problem of establishing a genetic connection between two individuals through a genomic segment that is inherited by both individuals from a recent common ancestor. IBD inference is an important preceding step in a variety of population genomic studies, ranging from demographic studies to linking genomic variation with phenotype and disease. The problem of accurate IBD detection has become increasingly challenging with the availability of large collections of human genotypes and genomes: Given a cohort\\'s size, a quadratic number of pairwise genome comparisons must be performed. Therefore, computation time and the false discovery rate can also scale quadratically. To enable accurate and efficient large-scale IBD detection, we present Parente2, a novel method for detecting IBD segments. Parente2 is based on an embedded log-likelihood ratio and uses a model that accounts for linkage disequilibrium by explicitly modeling haplotype frequencies. Parente2 operates directly on genotype data without the need to phase data prior to IBD inference. We evaluate Parente2\\'s performance through extensive simulations using real data, and we show that it provides substantially higher accuracy compared to previous state-of-the-art methods while maintaining high computational efficiency.
Manifestations of inflammatory bowel disease in patients of Haitian and Cape Verdean descent.
Stallwood, Christopher; Shergill, Karenpreet; Wu, Joseph; Farraye, Francis A; Miller, Hannah L
2015-07-01
Several studies have reported unique ethnic phenotypes of inflammatory bowel disease (IBD). An appreciation of disease manifestations in different populations may improve clinical outcomes. There are no studies examining IBD in patients of Haitian or Cape Verdean descent. We sought to define the IBD phenotype in these populations. This was a retrospective review comparing Haitian and Cape Verdean immigrant IBD patients to Caucasians, all receiving care at Boston Medical Center in Boston, Massachusetts, USA. The following variables were analyzed: family history, smoking history, vaccinations/cancer screening, age of diagnosis, disease duration, disease location, medication use, and complications. Thirty-one Haitians and 21 Cape Verdeans were matched to Caucasian controls. Haitians (mean age 42 years) and Cape Verdeans (mean age 47 years) with Crohn's disease were diagnosed with IBD later than Caucasians (mean age 31 years, p = 0.04 and 0.02, respectively). Haitians with Crohn's were less likely to have a history of tobacco use compared to Caucasians (13% vs. 51%, p = 0.02). Cape Verdeans with Crohn's were less likely to have perianal involvement (0% vs. 50%, p = 0.01). Haitians with IBD were less likely to have ever used glucocorticoids (48% vs. 76%, p = 0.02). There was no difference in vaccination rates, cancer screening, or disease complications. This study demonstrates differences in IBD presentation and disease course among Haitians and Cape Verdeans. Our results suggest a more mild disease in these ethnic groups. Future studies are needed to identify the influence of environmental factors.
Rain, winds and haze during the Huygens probe's descent to Titan's surface
Tomasko, M.G.; Archinal, B.; Becker, T.; Bezard, B.; Bushroe, M.; Combes, M.; Cook, D.; Coustenis, A.; De Bergh, C.; Dafoe, L.E.; Doose, L.; Doute, S.; Eibl, A.; Engel, S.; Gliem, F.; Grieger, B.; Holso, K.; Howington-Kraus, E.; Karkoschka, E.; Keller, H.U.; Kirk, R.; Kramm, R.; Kuppers, M.; Lanagan, P.; Lellouch, E.; Lemmon, M.; Lunine, J.; McFarlane, E.; Moores, J.; Prout, G.M.; Rizk, B.; Rosiek, M.; Rueffer, P.; Schroder, S.E.; Schmitt, B.; See, C.; Smith, P.; Soderblom, L.; Thomas, N.; West, R.
2005-01-01
The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. ?? 2005 Nature Publishing Group.
The detailed measurement of foot clearance by young adults during stair descent.
Telonio, A; Blanchet, S; Maganaris, C N; Baltzopoulos, V; McFadyen, B J
2013-04-26
Foot clearance is an important variable for understanding safe stair negotiation, but few studies have provided detailed measures of it. This paper presents a new method to calculate minimal shoe clearance during stair descent and compares it to previous literature. Seventeen healthy young subjects descended a five step staircase with step treads of 300 mm and step heights of 188 mm. Kinematic data were collected with an Optotrak system (model 3020) and three non-colinear infrared markers on the feet. Ninety points were digitized on the foot sole prior to data collection using a 6 marker probe and related to the triad of markers on the foot. The foot sole was reconstructed using the Matlab (version 7.0) "meshgrid" function and minimal distance to each step edge was calculated for the heel, toe and foot sole. Results showed significant differences in minimum clearance between sole, heel and toe, with the shoe sole being the closest and the toe the furthest. While the hind foot sole was closest for 69% of the time, the actual minimum clearance point on the sole did vary across subjects and staircase steps. This new method, and the findings on healthy young subjects, can be applied to future studies of other populations and staircase dimensions. Copyright © 2013 Elsevier Ltd. All rights reserved.
McCormack, Mark; Gui, Hongsheng; Ingason, Andrés; Speed, Doug; Wright, Galen E B; Zhang, Eunice J; Secolin, Rodrigo; Yasuda, Clarissa; Kwok, Maxwell; Wolking, Stefan; Becker, Felicitas; Rau, Sarah; Avbersek, Andreja; Heggeli, Kristin; Leu, Costin; Depondt, Chantal; Sills, Graeme J; Marson, Anthony G; Auce, Pauls; Brodie, Martin J; Francis, Ben; Johnson, Michael R; Koeleman, Bobby P C; Striano, Pasquale; Coppola, Antonietta; Zara, Federico; Kunz, Wolfram S; Sander, Josemir W; Lerche, Holger; Klein, Karl Martin; Weckhuysen, Sarah; Krenn, Martin; Gudmundsson, Lárus J; Stefánsson, Kári; Krause, Roland; Shear, Neil; Ross, Colin J D; Delanty, Norman; Pirmohamed, Munir; Carleton, Bruce C; Cendes, Fernando; Lopes-Cendes, Iscia; Liao, Wei-Ping; O'Brien, Terence J; Sisodiya, Sanjay M; Cherny, Stacey; Kwan, Patrick; Baum, Larry; Cavalleri, Gianpiero L
2018-01-23
To characterize, among European and Han Chinese populations, the genetic predictors of maculopapular exanthema (MPE), a cutaneous adverse drug reaction common to antiepileptic drugs. We conducted a case-control genome-wide association study of autosomal genotypes, including Class I and II human leukocyte antigen (HLA) alleles, in 323 cases and 1,321 drug-tolerant controls from epilepsy cohorts of northern European and Han Chinese descent. Results from each cohort were meta-analyzed. We report an association between a rare variant in the complement factor H-related 4 ( CFHR4 ) gene and phenytoin-induced MPE in Europeans ( p = 4.5 × 10 -11 ; odds ratio [95% confidence interval] 7 [3.2-16]). This variant is in complete linkage disequilibrium with a missense variant (N1050Y) in the complement factor H ( CFH ) gene. In addition, our results reinforce the association between HLA-A*31:01 and carbamazepine hypersensitivity. We did not identify significant genetic associations with MPE among Han Chinese patients. The identification of genetic predictors of MPE in CFHR4 and CFH, members of the complement factor H-related protein family, suggest a new link between regulation of the complement system alternative pathway and phenytoin-induced hypersensitivity in European-ancestral patients. Copyright © 2017 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.
Of African Descent? Blackness and the Concept of Origins in Cultural Perspectives
Directory of Open Access Journals (Sweden)
Sarah Abel
2018-03-01
Full Text Available Over the past decade, the DNA ancestry-testing industry—based largely in the United States—has experienced a huge upsurge in popularity, thanks partly to rapidly developing technologies and the falling prices of products. Meanwhile, the notion of “genetic genealogy” has been strongly endorsed by popular television documentary shows in the US, particularly vis-à-vis African-American roots-seekers—for whom these products are offered as a means to discover one’s ancestral “ethnic” origins, thereby “reversing the Middle Passage.” Yet personalized DNA ancestry tests have not had the same reception among people of African descent in other societies that were historically affected by slavery. This paper outlines and contextualizes these divergent responses by examining and comparing the cultural and political meanings that are attached to notions of origin, as well as the way that Blackness has been defined and articulated, in three different settings: the United States, France and Brazil.
Shell, Alyssa Marie; Peek, M. Kristen; Eschbach, Karl
2014-01-01
Substantial research shows that increased Hispanic neighborhood concentration is associated with several beneficial health outcomes including lower adult mortality, better self-rated health, and fewer respiratory problems. Literature on the relationship of Hispanic composition and depressive symptoms is more equivocal. In addition, few studies have directly investigated hypothesized mechanisms of this relationship. This study uses data from a probability sample of 1,238 Mexican-descent adults living in 48 neighborhoods in Texas City, Texas. Multilevel regression models investigate whether Hispanic neighborhood composition is associated with fewer depressive symptoms. This study also investigates whether social support, perceived discrimination, and perceived stress mediate or moderate the relationship, and whether results differ by primary language used at home. We find that individuals living in high Hispanic composition neighborhoods experience fewer depressive symptoms than individuals in low Hispanic composition neighborhoods. In addition, we find that these beneficial effects only apply to respondents who speak English. Social support, perceived discrimination, and perceived stress mediate the Hispanic composition-depressive symptoms relationship. In addition, discrimination and stress moderate the relationship between Hispanic composition and depressive symptoms. Our findings support theories linking higher neighborhood Hispanic composition and better mental health, and suggest that Spanish language use, social support, discrimination and stress may play important roles in the Hispanic composition-depressive symptoms relationship. PMID:24355471
Multidisciplinary Tool for Systems Analysis of Planetary Entry, Descent, and Landing
Samareh, Jamshid A.
2011-01-01
Systems analysis of a planetary entry (SAPE), descent, and landing (EDL) is a multidisciplinary activity in nature. SAPE improves the performance of the systems analysis team by automating and streamlining the process, and this improvement can reduce the errors that stem from manual data transfer among discipline experts. SAPE is a multidisciplinary tool for systems analysis of planetary EDL for Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Titan. It performs EDL systems analysis for any planet, operates cross-platform (i.e., Windows, Mac, and Linux operating systems), uses existing software components and open-source software to avoid software licensing issues, performs low-fidelity systems analysis in one hour on a computer that is comparable to an average laptop, and keeps discipline experts in the analysis loop. SAPE uses Python, a platform-independent, open-source language, for integration and for the user interface. Development has relied heavily on the object-oriented programming capabilities that are available in Python. Modules are provided to interface with commercial and government off-the-shelf software components (e.g., thermal protection systems and finite-element analysis). SAPE currently includes the following analysis modules: geometry, trajectory, aerodynamics, aerothermal, thermal protection system, and interface for structural sizing.
Qyyum, Muhammad Abdul; Long, Nguyen Van Duc; Minh, Le Quang; Lee, Moonyong
2018-01-01
Design optimization of the single mixed refrigerant (SMR) natural gas liquefaction (LNG) process involves highly non-linear interactions between decision variables, constraints, and the objective function. These non-linear interactions lead to an irreversibility, which deteriorates the energy efficiency of the LNG process. In this study, a simple and highly efficient hybrid modified coordinate descent (HMCD) algorithm was proposed to cope with the optimization of the natural gas liquefaction process. The single mixed refrigerant process was modeled in Aspen Hysys® and then connected to a Microsoft Visual Studio environment. The proposed optimization algorithm provided an improved result compared to the other existing methodologies to find the optimal condition of the complex mixed refrigerant natural gas liquefaction process. By applying the proposed optimization algorithm, the SMR process can be designed with the 0.2555 kW specific compression power which is equivalent to 44.3% energy saving as compared to the base case. Furthermore, in terms of coefficient of performance (COP), it can be enhanced up to 34.7% as compared to the base case. The proposed optimization algorithm provides a deep understanding of the optimization of the liquefaction process in both technical and numerical perspectives. In addition, the HMCD algorithm can be employed to any mixed refrigerant based liquefaction process in the natural gas industry.
En Route Descent Advisor Multi-Sector Planning Using Active and Provisional Controller Plans
Vivona, Robert; Green, Steven
2003-01-01
As decision support tools are developed to support controllers in complex air traffic control environments, new approaches to maintaining situation awareness and managing traffic planning must be developed to handle the ever-increasing amounts of alerting and advisory data. Within high-density metering and other environments where flight path changes are the rule, not the exception, and where interactions between these changes are required, current trial planning approaches are limited by potential increases in workload. The Enroute Descent Advisor (EDA) is a set of decision support tool capabilities for managing high-density en route traffic subject to metering restrictions. The EDA system s novel approach builds aircraft plans from combinations of user intent data and builds controller plans from combinations of aircraft plans to effectively maintain situation awareness during traffic planning. By maintaining both active (current) and provisional (proposed) controller plans, EDA supports controllers in coordinated traffic planning both within and between sectors. Ultimately, EDA s multi-sector planning approach will facilitate a transition from current sector-oriented operations to a new trajectory-oriented paradigm, enabling new levels of efficiency and collaboration in air traffic control.
Genome-wide patterns of identity-by-descent sharing in the French Canadian founder population.
Gauvin, Héloïse; Moreau, Claudia; Lefebvre, Jean-François; Laprise, Catherine; Vézina, Hélène; Labuda, Damian; Roy-Gagnon, Marie-Hélène
2014-06-01
In genetics the ability to accurately describe the familial relationships among a group of individuals can be very useful. Recent statistical tools succeeded in assessing the degree of relatedness up to 6-7 generations with good power using dense genome-wide single-nucleotide polymorphism data to estimate the extent of identity-by-descent (IBD) sharing. It is therefore important to describe genome-wide patterns of IBD sharing for more remote and complex relatedness between individuals, such as that observed in a founder population like Quebec, Canada. Taking advantage of the extended genealogical records of the French Canadian founder population, we first compared different tools to identify regions of IBD in order to best describe genome-wide IBD sharing and its correlation with genealogical characteristics. Results showed that the extent of IBD sharing identified with FastIBD correlates best with relatedness measured using genealogical data. Total length of IBD sharing explained 85% of the genealogical kinship's variance. In addition, we observed significantly higher sharing in pairs of individuals with at least one inbred ancestor compared with those without any. Furthermore, patterns of IBD sharing and average sharing were different across regional populations, consistent with the settlement history of Quebec. Our results suggest that, as expected, the complex relatedness present in founder populations is reflected in patterns of IBD sharing. Using these patterns, it is thus possible to gain insight on the types of distant relationships in a sample from a founder population like Quebec.
Atmosphere Assessment for MARS Science Laboratory Entry, Descent and Landing Operations
Cianciolo, Alicia D.; Cantor, Bruce; Barnes, Jeff; Tyler, Daniel, Jr.; Rafkin, Scot; Chen, Allen; Kass, David; Mischna, Michael; Vasavada, Ashwin R.
2013-01-01
On August 6, 2012, the Mars Science Laboratory rover, Curiosity, successfully landed on the surface of Mars. The Entry, Descent and Landing (EDL) sequence was designed using atmospheric conditions estimated from mesoscale numerical models. The models, developed by two independent organizations (Oregon State University and the Southwest Research Institute), were validated against observations at Mars from three prior years. In the weeks and days before entry, the MSL "Council of Atmospheres" (CoA), a group of atmospheric scientists and modelers, instrument experts and EDL simulation engineers, evaluated the latest Mars data from orbiting assets including the Mars Reconnaissance Orbiter's Mars Color Imager (MARCI) and Mars Climate Sounder (MCS), as well as Mars Odyssey's Thermal Emission Imaging System (THEMIS). The observations were compared to the mesoscale models developed for EDL performance simulation to determine if a spacecraft parameter update was necessary prior to entry. This paper summarizes the daily atmosphere observations and comparison to the performance simulation atmosphere models. Options to modify the atmosphere model in the simulation to compensate for atmosphere effects are also presented. Finally, a summary of the CoA decisions and recommendations to the MSL project in the days leading up to EDL is provided.
A Rigid Mid-Lift-to-Drag Ratio Approach to Human Mars Entry, Descent, and Landing
Cerimele, Christopher J.; Robertson, Edward A.; Sostaric, Ronald R.; Campbell, Charles H.; Robinson, Phil; Matz, Daniel A.; Johnson, Breanna J.; Stachowiak, Susan J.; Garcia, Joseph A.; Bowles, Jeffrey V.;
2017-01-01
Current NASA Human Mars architectures require delivery of approximately 20 metric tons of cargo to the surface in a single landing. A proposed vehicle type for performing the entry, descent, and landing at Mars associated with this architecture is a rigid, enclosed, elongated lifting body shape that provides a higher lift-to-drag ratio (L/D) than a typical entry capsule, but lower than a typical winged entry vehicle (such as the Space Shuttle Orbiter). A rigid Mid-L/D shape has advantages for large mass Mars EDL, including loads management, range capability during entry, and human spaceflight heritage. Previous large mass Mars studies have focused more on symmetric and/or circular cross-section Mid-L/D shapes such as the ellipsled. More recent work has shown performance advantages for non-circular cross section shapes. This paper will describe efforts to design a rigid Mid-L/D entry vehicle for Mars which shows mass and performance improvements over previous Mid-L/D studies. The proposed concept, work to date and evolution, forward path, and suggested future strategy are described.
Low Cost Entry, Descent, and Landing (EDL) Instrumentation for Planetary Missions
Hwang, H. H.; Munk, M. M.; Dillman, R. A.; Mahzari, M.; Swanson, G. T.; White, T. R.
2016-01-01
Missions that involve traversing through a planetary atmosphere are unique opportunities that require elements of entry, descent, and landing (EDL). Many aspects of the EDL sequence are qualified using analysis and simulation due to the inability to conduct appropriate ground tests, however validating flight data are often lacking, especially for missions not involving Earth re-entry. NASA has made strategic decisions to collect EDL flight data in order to improve future mission designs. For example, MEDLI1 and EFT-1 gathered hypersonic pressure and in-depth temperature data in the thermal protection system (TPS). However, the ability to collect EDL flight data from the smaller competed missions, such as Discovery and New Frontiers, has been limited in part due to the Principal Investigator-managed cost-caps (PIMCC). The recent NASA decision to consider EDL instrumentation earlier in the mission design cycle led to the inclusion of a requirement in the Discovery 2014 Announcement of Opportunity which requires all missions that involve EDL to include an Engineering Science Investigation (ESI).2 The ESI would involve sensors for aerothermal environment and TPS; atmosphere, aerodynamics, and flight dynamics; atmospheric decelerator; and/or vehicle structure.3 The ESI activity would be funded outside of the PIMCC.
Fringe instability in constrained soft elastic layers.
Lin, Shaoting; Cohen, Tal; Zhang, Teng; Yuk, Hyunwoo; Abeyaratne, Rohan; Zhao, Xuanhe
2016-11-04
Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer's thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width. In this case, the middle portion along the layer's thickness elongates nearly uniformly while the constrained fringe portions of the layer deform nonuniformly. When the applied stretch reaches a critical value, the exposed free surfaces of the fringe portions begin to undulate periodically without debonding from the rigid bodies, giving the fringe instability. We use experiments, theory and numerical simulations to quantitatively explain the fringe instability and derive scaling laws for its critical stress, critical strain and wavelength. We show that in a force controlled setting the elastic fingering instability is associated with a snap-through buckling that does not exist for the fringe instability. The discovery of the fringe instability will not only advance the understanding of mechanical instabilities in soft materials but also have implications for biological and engineered adhesives and joints.
Energy transfer and constrained simulations in isotropic turbulence
Jimenez, Javier
1993-01-01
The defining characteristic of turbulent flows is their ability to dissipate energy, even in the limit of zero viscosity. The Euler equations, if constrained in such a way that the velocity derivatives remain bounded, conserve energy. But when they arise as the limit of the Navier-Stokes (NS) equations, when the Reynolds number goes to infinity, there is persuasive empirical evidence that the gradients become singular as just the right function of Re for the dissipation to remain non-zero and to approach a well defined limit. It is generally believed that this limiting value of the dissipation is a property of the Euler equations themselves, independent of the particular dissipative mechanism involved, and that it can be normalized with the large scale properties of the turbulent flow (e.g. the kinetic energy per unit volume u'(exp 2)/2, and the integral scale L) without reference to the Reynolds number or to other dissipative quantities. This is usually taken to imply that the low wave number end of the energy spectrum, far from the dissipative range, is also independent of the particular mechanism chosen to dispose of the energy transfer. In the following sections, we present some numerical experiments on the effect of substituting different dissipation models into the truncated Euler equations. We will see that the effect is mainly felt in the 'near dissipation' range of the energy spectrum, but that this range can be quite wide in some cases, contaminating a substantial range of wave numbers. In the process, we will develop a 'practical' approximation to the subgrid energy transfer in isotropic turbulence, and we will gain insight into the structure of the nonlinear interactions among turbulent scales of comparable size, and into the nature of energy backscatter. Some considerations on future research directions are offered at the end.
Strain gradient effects on cyclic plasticity
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Legarth, Brian Nyvang
2010-01-01
Size effects on the cyclic shear response are studied numerically using a recent higher order strain gradient visco-plasticity theory accounting for both dissipative and energetic gradient hardening. Numerical investigations of the response under cyclic pure shear and shear of a finite slab between...... rigid platens have been carried out, using the finite element method. It is shown for elastic–perfectly plastic solids how dissipative gradient effects lead to increased yield strength, whereas energetic gradient contributions lead to increased hardening as well as a Bauschinger effect. For linearly...... hardening materials it is quantified how dissipative and energetic gradient effects promote hardening above that of conventional predictions. Usually, increased hardening is attributed to energetic gradient effects, but here it is found that also dissipative gradient effects lead to additional hardening...
Directory of Open Access Journals (Sweden)
P Veena
2016-01-01
Full Text Available Two rare complications of twin gestation, namely, conjoined twins and interlocking of twins, manifested as arrest of descent in the second stage of labor. This article reports in detail about how the diagnosis of conjoined twins was missed by ultrasonogram and interlocking of twins unusually occurred in diamniotic twins. The management of these rare conditions is also mentioned to aid readers to act accordingly in rare undiagnosed cases.
Trushlyakov, V.; Iordan, Yu; Davydovich, D.; Zharikov, K.; Dron, M.
2018-01-01
The thermal loading physical simulation in the experimental wind tunnel on the design element of the payload fairing made of carbon fiber was done. The experimental study is given in the speed range below 70 m/s, which corresponds to the interval of heights of the descent trajectory of the payload fairing half below 10 km. The values of heat transfer coefficient are obtained. The analysis of the results is carried out.
Decomposing the land-use specific response of plant functional traits along environmental gradients.
Fontana, Veronika; Kohler, Marina; Niedrist, Georg; Bahn, Michael; Tappeiner, Ulrike; Frenck, Georg
2017-12-01
Environmental conditions affect functional trait variability within communities and thus shape ecosystem properties. With the ability of plants to adapt morphologically and physiologically to changing abiotic conditions, gradient analysis was shown to be a suitable tool to identify the drivers which determine trait values. Apart from direct environmental drivers and indirect gradients such as elevation, also anthropogenic effects (e.g. irrigation, grazing) can influence trait variability. Our aim was to assess the interactive effects of different environmental drivers on major plant traits and to investigate how these are modulated within two different land-use types (hay meadow vs. pasture). An elevational gradient spanning 1000m was decomposed into its underlying direct components (temperature, water input, length of growing season) for the investigation of gradual responses of five prominent functional traits (aboveground dry weight (AGDW), vegetative height (VegHt), specific leaf area (SLA), leaf dry matter content (LDMC), leaf nitrogen concentration (LNC)) for key species from two functional groups (grasses, forbs) in the two land-use/management regimes. The present study revealed that the detailed analysis of single direct gradients provides substantial additional information on trait response which remains hidden or is even reversed if only indirect gradients such as elevation are analysed. However, trait response to the combination of the three direct gradients aligned surprisingly well with trait response to the indirect gradient underpinning the adequate representation of temperature, water input and length of growing season by elevation. The response of traits significantly depended on the management regime and corresponding intensity which was shown to play an overriding role and constrained and attenuated response ranges of traits to climatic gradients. Copyright © 2017 Elsevier B.V. All rights reserved.
Local adaptation at range edges: comparing elevation and latitudinal gradients.
Halbritter, A H; Billeter, R; Edwards, P J; Alexander, J M
2015-10-01
Local adaptation at range edges influences species' distributions and how they respond to environmental change. However, the factors that affect adaptation, including gene flow and local selection pressures, are likely to vary across different types of range edge. We performed a reciprocal transplant experiment to investigate local adaptation in populations of Plantago lanceolata and P. major from central locations in their European range and from their latitudinal and elevation range edges (in northern Scandinavia and Swiss Alps, respectively). We also characterized patterns of genetic diversity and differentiation in populations using molecular markers. Range-centre plants of P. major were adapted to conditions at the range centre, but performed similarly to range-edge plants when grown at the range edges. There was no evidence for local adaptation when comparing central and edge populations of P. lanceolata. However, plants of both species from high elevation were locally adapted when compared with plants from high latitude, although the reverse was not true. This asymmetry was associated with greater genetic diversity and less genetic differentiation over the elevation gradient than over the latitudinal gradient. Our results suggest that adaptation in some range-edge populations could increase their performance following climate change. However, responses are likely to differ along elevation and latitudinal gradients, with adaptation more likely at high-elevation. Furthermore, based upon these results, we suggest that gene flow is unlikely to constrain adaptation in range-edge populations of these species. © 2015 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2015 European Society For Evolutionary Biology.
Piasečná, Karin; Pončová, Alena; Tejedo, Miguel; Gvoždík, Lumír
2015-08-01
Many ectotherms employ diverse behavioral adjustments to effectively buffer the spatio-temporal variation in environmental temperatures, whereas others remain passive to thermal heterogeneity. Thermoregulatory studies are frequently performed on species living in thermally benign habitats, which complicate understanding of the thermoregulation-thermoconformity continuum. The need for new empirical data from ectotherms exposed to thermally challenging conditions requires the evaluation of available methods for quantifying thermoregulatory strategies. We evaluated the applicability of various thermoregulatory indices using fire salamander larvae, Salamandra salamandra, in two aquatic habitats, a forest pool and well, as examples of disparate thermally-constrained environments. Water temperatures in the well were lower and less variable than in the pool. Thermal conditions prevented larvae from reaching their preferred body temperature range in both water bodies. In contrast to their thermoregulatory abilities examined in a laboratory thermal gradient, field body temperatures only matched the mean and range of operative temperatures, showing thermal passivity of larvae in both habitats. Despite apparent thermoconformity, thermoregulatory indices indicated various strategies from active thermoregulation, to thermoconformity, and even thermal evasion, which revealed their limited applicability under thermally-constrained conditions. Salamander larvae abandoned behavioral thermoregulation despite varying opportunities to increase their body temperature above average water temperatures. Thermoconformity represents a favored strategy in these ectotherms living in more thermally-constrained environments than those examined in previous thermoregulatory studies. To understand thermal ecology and its impact on population dynamics, the quantification of thermoregulatory strategies of ectotherms in thermally-constrained habitats requires the careful choice of an appropriate
Statistical mechanics of budget-constrained auctions
International Nuclear Information System (INIS)
Altarelli, F; Braunstein, A; Realpe-Gomez, J; Zecchina, R
2009-01-01
Finding the optimal assignment in budget-constrained auctions is a combinatorial optimization problem with many important applications, a notable example being in the sale of advertisement space by search engines (in this context the problem is often referred to as the off-line AdWords problem). On the basis of the cavity method of statistical mechanics, we introduce a message-passing algorithm that is capable of solving efficiently random instances of the problem extracted from a natural distribution, and we derive from its properties the phase diagram of the problem. As the control parameter (average value of the budgets) is varied, we find two phase transitions delimiting a region in which long-range correlations arise
Scheduling of resource-constrained projects
Klein, Robert
2000-01-01
Project management has become a widespread instrument enabling organizations to efficiently master the challenges of steadily shortening product life cycles, global markets and decreasing profit margins. With projects increasing in size and complexity, their planning and control represents one of the most crucial management tasks. This is especially true for scheduling, which is concerned with establishing execution dates for the sub-activities to be performed in order to complete the project. The ability to manage projects where resources must be allocated between concurrent projects or even sub-activities of a single project requires the use of commercial project management software packages. However, the results yielded by the solution procedures included are often rather unsatisfactory. Scheduling of Resource-Constrained Projects develops more efficient procedures, which can easily be integrated into software packages by incorporated programming languages, and thus should be of great interest for practiti...
Spatially constrained propulsion in jumping archer fish
Mendelson, Leah; Techet, Alexandra
2016-11-01
Archer fish jump multiple body lengths out of the water for prey capture with impressive accuracy. Their remarkable aim is facilitated by jumping from a stationary position directly below the free surface. As a result of this starting position, rapid acceleration to a velocity sufficient for reaching the target occurs with only a body length to travel before the fish leaves the water. Three-dimensional measurements of jumping kinematics and volumetric velocimetry using Synthetic Aperture PIV highlight multiple strategies for such spatially constrained acceleration. Archer fish rapidly extend fins at jump onset to increase added mass forces and modulate their swimming kinematics to minimize wasted energy when the body is partially out of the water. Volumetric measurements also enable assessment of efficiency during a jump, which is crucial to understanding jumping's role as an energetically viable hunting strategy for the fish.
Neuroevolutionary Constrained Optimization for Content Creation
DEFF Research Database (Denmark)
Liapis, Antonios; Yannakakis, Georgios N.; Togelius, Julian
2011-01-01
This paper presents a constraint-based procedural content generation (PCG) framework used for the creation of novel and high-performing content. Specifically, we examine the efficiency of the framework for the creation of spaceship design (hull shape and spaceship attributes such as weapon...... and thruster types and topologies) independently of game physics and steering strategies. According to the proposed framework, the designer picks a set of requirements for the spaceship that a constrained optimizer attempts to satisfy. The constraint satisfaction approach followed is based on neuroevolution......; Compositional Pattern-Producing Networks (CPPNs) which represent the spaceship’s design are trained via a constraint-based evolutionary algorithm. Results obtained in a number of evolutionary runs using a set of constraints and objectives show that the generated spaceships perform well in movement, combat...
Shape space exploration of constrained meshes
Yang, Yongliang
2011-12-12
We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.
Constraining dark sectors with monojets and dijets
International Nuclear Information System (INIS)
Chala, Mikael; Kahlhoefer, Felix; Nardini, Germano; Schmidt-Hoberg, Kai; McCullough, Matthew
2015-03-01
We consider dark sector particles (DSPs) that obtain sizeable interactions with Standard Model fermions from a new mediator. While these particles can avoid observation in direct detection experiments, they are strongly constrained by LHC measurements. We demonstrate that there is an important complementarity between searches for DSP production and searches for the mediator itself, in particular bounds on (broad) dijet resonances. This observation is crucial not only in the case where the DSP is all of the dark matter but whenever - precisely due to its sizeable interactions with the visible sector - the DSP annihilates away so efficiently that it only forms a dark matter subcomponent. To highlight the different roles of DSP direct detection and LHC monojet and dijet searches, as well as perturbativity constraints, we first analyse the exemplary case of an axial-vector mediator and then generalise our results. We find important implications for the interpretation of LHC dark matter searches in terms of simplified models.
Perceived visual speed constrained by image segmentation
Verghese, P.; Stone, L. S.
1996-01-01
Little is known about how or where the visual system parses the visual scene into objects or surfaces. However, it is generally assumed that the segmentation and grouping of pieces of the image into discrete entities is due to 'later' processing stages, after the 'early' processing of the visual image by local mechanisms selective for attributes such as colour, orientation, depth, and motion. Speed perception is also thought to be mediated by early mechanisms tuned for speed. Here we show that manipulating the way in which an image is parsed changes the way in which local speed information is processed. Manipulations that cause multiple stimuli to appear as parts of a single patch degrade speed discrimination, whereas manipulations that perceptually divide a single large stimulus into parts improve discrimination. These results indicate that processes as early as speed perception may be constrained by the parsing of the visual image into discrete entities.
How Our Biology Constrains Our Science
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Vlerick Michael
2017-04-01
Full Text Available Reasoning from a naturalistic perspective, viewing the mind as an evolved biological organ with a particular structure and function, a number of influential philosophers and cognitive scientists claim that science is constrained by human nature. How exactly our genetic constitution constrains scientific representations of the world remains unclear. This is problematic for two reasons. Firstly, it often leads to the unwarranted conclusion that we are cognitively closed to certain aspects or properties of the world. Secondly, it stands in the way of a nuanced account of the relationship between our cognitive and perceptual wiring and scientific theory. In response, I propose a typology or classification of the different kinds of biological constraints and their sources on science. Using Boden’s (1990 notion of a conceptual space, I distinguish between constraints relating to the ease with which we can reach representations within our conceptual space (which I call ‘biases’ and constraints causing possible representations to fall outside of our conceptual space. This last kind of constraints does not entail that some aspects or properties of the world cannot be represented by us – as argued by advocates of ‘cognitive closure’ – merely that some ways of representing the world are inaccessible to us. It relates to what Clark (1986 and Rescher (1990 have framed as ‘the alien scientist hypothesis’ (the possibility that alien scientists, endowed with radically different cognitive abilities, could produce representations of the world that are unintelligible to us. The purpose of this typology is to provide some much needed clarity and structure to the debate about biological constraints on science.
Wavefront reconstruction from its gradients.
Talmi, Amos; Ribak, Erez N
2006-02-01
Wavefronts reconstructed from measured gradients are composed of a straightforward integration of the measured data, plus a correction term that disappears when there are no measurement errors. For regions of any shape, this term is a solution of Poisson's equation with Dirichlet conditions (V = 0 on the boundaries). We show that for rectangular regions, the correct solution is not a periodic one, but one expressed with Fourier cosine series. The correct solution has a lower variance than the periodic Fourier transform solution. Similar formulas exist for a circular region with obscuration. We present a near-optimal solution that is much faster than fast-Fourier-transform methods. By use of diagonal multigrid methods, a single iteration brings the correction term to within a standard deviation of 0.08, two iterations, to within 0.0064, etc.
Covariance Analysis Tool (G-CAT) for Computing Ascent, Descent, and Landing Errors
Boussalis, Dhemetrios; Bayard, David S.
2013-01-01
G-CAT is a covariance analysis tool that enables fast and accurate computation of error ellipses for descent, landing, ascent, and rendezvous scenarios, and quantifies knowledge error contributions needed for error budgeting purposes. Because GCAT supports hardware/system trade studies in spacecraft and mission design, it is useful in both early and late mission/ proposal phases where Monte Carlo simulation capability is not mature, Monte Carlo simulation takes too long to run, and/or there is a need to perform multiple parametric system design trades that would require an unwieldy number of Monte Carlo runs. G-CAT is formulated as a variable-order square-root linearized Kalman filter (LKF), typically using over 120 filter states. An important property of G-CAT is that it is based on a 6-DOF (degrees of freedom) formulation that completely captures the combined effects of both attitude and translation errors on the propagated trajectories. This ensures its accuracy for guidance, navigation, and control (GN&C) analysis. G-CAT provides the desired fast turnaround analysis needed for error budgeting in support of mission concept formulations, design trade studies, and proposal development efforts. The main usefulness of a covariance analysis tool such as G-CAT is its ability to calculate the performance envelope directly from a single run. This is in sharp contrast to running thousands of simulations to obtain similar information using Monte Carlo methods. It does this by propagating the "statistics" of the overall design, rather than simulating individual trajectories. G-CAT supports applications to lunar, planetary, and small body missions. It characterizes onboard knowledge propagation errors associated with inertial measurement unit (IMU) errors (gyro and accelerometer), gravity errors/dispersions (spherical harmonics, masscons), and radar errors (multiple altimeter beams, multiple Doppler velocimeter beams). G-CAT is a standalone MATLAB- based tool intended to
Energy Technology Data Exchange (ETDEWEB)
Der Nigohossian, G. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1967-02-15
The electrical leads used to introduce a current into a cryostat cause a heat influx due to thermal conduction and to Joule heating. It is very important to be able to minimize this flux. Theoretical calculation of optimized leads takes into account the varying heat and electrical conductivities of the leads as well as the heat exchange coefficient with the effluent gas. Practical results have been summarized in different tables which permit for a specific material i.e. copper, aluminium, brass, stainless steel with the intensity and end temperatures being known (i.e. 4,2 or 18,5 deg. K at the cold end; 77,295 or 320 deg. K at the warm end) to deduce the minimum heat flow and the length-cross section ratio of the optimized leads. A general method is indicated, which would allow to solve the same problem for other materials. (author) [French] Les conducteurs electriques assurant la liaison d'appareillages situes dans des cryostats apportent tant par effet Joule que par conductibilite thermique une certaine quantite de chaleur qu'il est tres important de pouvoir minimiser. L'etude theorique de l'optimisation des descentes de courant tient compte des variations des conductibilites thermique et electrique ainsi que de l'influence des echanges avec le gaz. Pratiquement les resultats ont ete resumes dans differents tableaux ce qui permet, pour un materiau donne tel que cuivre, aluminium, laiton, acier inoxydable, connaissant l'intensite et les temperatures d'extremites 4,2 et 18,5 deg. K d'une part, et 77,295 et 330 deg. K d'autre part, de deduire la consommation minimale et le rapport longueur-section d'un conducteur optimise. Une methode generale est indiquee, qui permet de resoudre le probleme pour d'autres materiaux. (auteur)
Performance of conventional and X2® prosthetic knees during slope descent.
Bell, Elizabeth M; Pruziner, Alison L; Wilken, Jason M; Wolf, Erik J
2016-03-01
Individuals with transfemoral amputation often have difficulty descending sloped surfaces due to increased lower extremity range of motion and torque requirements. The X2®, a new microprocessor-controlled prosthetic knee, claims to improve gait over sloped terrain. The aim of this study was to evaluate how experienced prosthesis users descended a sloped surface using the X2®, compared to a conventional knee, either mechanical (MECH) or microprocessor (MP). Descent technique and biomechanics were assessed in 21 service members with unilateral transfemoral amputation as they descended an instrumented 10° slope at a self-selected walking velocity. Use of the X2® in the MECH group resulted in greater hill assessment scores (8.5 to 11.0, P=0.026), due primarily to decreased reliance on handrail use. The use of the X2® in the MP group increased prosthetic knee flexion to a median of 6.4° at initial contact (P=0.002) and 73.7° in swing (P=0.005), contributing to longer prosthetic limb steps (P=0.024) and increased self-selected velocity (P=0.041). Additionally, the use of the X2® in the MP group increased prosthetic limb impact peaks (11.6N/kg, P=0.004), improving impact peak symmetry to -1.3% (P=0.004). Decreased reliance on handrail use as MECH users descended in the X2® indicate improved function and perhaps greater confidence in the device. Additional biomechanical improvements for existing MP users suggest potential longer-term benefits with regard to intact limb health and overuse injuries. Copyright © 2016 Elsevier Ltd. All rights reserved.
Conflation of Short Identity-by-Descent Segments Bias Their Inferred Length Distribution
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Charleston W. K. Chiang
2016-05-01
Full Text Available Identity-by-descent (IBD is a fundamental concept in genetics with many applications. In a common definition, two haplotypes are said to share an IBD segment if that segment is inherited from a recent shared common ancestor without intervening recombination. Segments several cM long can be efficiently detected by a number of algorithms using high-density SNP array data from a population sample, and there are currently efforts to detect shorter segments from sequencing. Here, we study a problem of identifiability: because existing approaches detect IBD based on contiguous segments of identity-by-state, inferred long segments of IBD may arise from the conflation of smaller, nearby IBD segments. We quantified this effect using coalescent simulations, finding that significant proportions of inferred segments 1–2 cM long are results of conflations of two or more shorter segments, each at least 0.2 cM or longer, under demographic scenarios typical for modern humans for all programs tested. The impact of such conflation is much smaller for longer (> 2 cM segments. This biases the inferred IBD segment length distribution, and so can affect downstream inferences that depend on the assumption that each segment of IBD derives from a single common ancestor. As an example, we present and analyze an estimator of the de novo mutation rate using IBD segments, and demonstrate that unmodeled conflation leads to underestimates of the ages of the common ancestors on these segments, and hence a significant overestimate of the mutation rate. Understanding the conflation effect in detail will make its correction in future methods more tractable.
Microsatellite studies on an isolated population of African descent in the Brazilian state of Bahia
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Ana Angélica Leal Barbosa
2006-01-01
Full Text Available The African descent population of the Bananal community in the Brazilian state of Bahia (BA was characterized as a genetic isolate and analyzed for some short tandem repeat (STR microsatellite autosomic polymorphic loci (CSF1PO, TH01, TPOX, F13A1, FESFPS and vWA. These genetic variants were further compared to data obtained from an urban sample from the town of Jequié (BA regarding demographic and anthropogenetic aspects. The Bananal sample comprised 32 unrelated individuals whereas Jequié was represented by 76 individuals. The Bananal Negroid Phenotypic Index (NPI was 0.98 and the Negroid Cultural Index (NCI 0.24. Consanguineous marriages occurred at a frequency of 34.61% and the F value was 0.0126. All six loci studied were in Hardy-Weinberg Equilibrium (p > 0.05. The genotypic and allele frequencies of the CSF1PO and vWA loci were similar. In the Bananal population the genic diversity of the THO1 locus was 66.8% and that of the F13A1 locus was 83.7%. The estimated ethnic racial admixture was 81% African and 19% Amerindian. The multiple correlation coefficient (R² indicated adequate adaptation (99%. Total genetic variation for the six loci was 82.9% with an index of 6.7% for population subdivision (G ST' = 0.067. Anthropologic data and results obtained from the allele frequencies of the loci studied are indicative of a genetic isolate in Bananal, reminiscent of the a 'quilombo community' (i.e. one founded by run away slaves.
Undiagnosed metabolic syndrome and other adverse effects among clozapine users of Xhosa descent
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N Faasen
2014-07-01
Full Text Available Background. Clozapine use is known to be associated with significant side-effects, including prolongation of the QT-interval, agranulocytosis and metabolic syndrome. However, few data exist on the prevalence of clozapine side-effects in patients of Xhosa descent. Objective. To gather data from Xhosa patients with schizophrenia to establish the prevalence of clozapine side-effects in this population. Methods. Twenty-nine Xhosa patients with schizophrenia (as per the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR who had been receiving clozapine treatment for >1 year on an outpatient basis were selected for inclusion. All patients were participating in a genetics study in the Cape Metropolitan area. The participants were evaluated for the presence of side-effects (tests including an electrocardiogram, white blood cell count (WCC and fasting blood glucose. Results. The prevalence of metabolic syndrome was 44.8% (95% confidence interval (CI 26.7 - 62.9 and of undiagnosed diabetes mellitus 13.8% (95% CI 1.24 - 26.34. There was a significant association between metabolic syndrome and body mass index (BMI (p440 ms. There was an association between the duration of clozapine treatment and QT-interval (with Bazett’s correction. Conclusion. The high prevalence of metabolic syndrome and undiagnosed diabetes mellitus in this sample points to a need to monitor glucose levels and BMI on a regular basis. A larger study should be done to accurately quantify the differences in prevalence of side-effects between population groups.
Celis-Morales, Carlos A; Perez-Bravo, Francisco; Ibañes, Luis; Sanzana, Ruth; Hormazabal, Edison; Ulloa, Natalia; Calvo, Carlos; Bailey, Mark E S; Gill, Jason M R
2011-01-01
Effects of urbanisation on diabetes risk appear to be greater in indigenous populations worldwide than in populations of European origin, but the reasons are unclear. This cross-sectional study aimed to determine whether the effects of environment (Rural vs. Urban), adiposity, fitness and lifestyle variables on insulin resistance differed between individuals of indigenous Mapuche origin compared to those of European origin in Chile. 123 Rural Mapuche, 124 Urban Mapuche, 91 Rural European and 134 Urban European Chilean adults had blood taken for determination of HOMA-estimated insulin resistance (HOMA(IR)) and underwent assessment of physical activity/sedentary behaviour (using accelerometry), cardiorespiratory fitness, dietary intake and body composition. General linear models were used to determine interactions with ethnicity for key variables. There was a significant "ethnicity x environment" interaction for HOMA(IR) (Mean±SD; Rural Mapuche: 1.65±2.03, Urban Mapuche: 4.90±3.05, Rural European: 0.82±0.61, Urban European: 1.55±1.34, p((interaction)) = 0.0003), such that the effect of urbanisation on HOMA(IR) was greater in Mapuches than Europeans. In addition, there were significant interactions (all pMapuches compared to Europeans, an observation that persisted after adjustment for potential confounders. Urbanisation, adiposity, physical activity and sedentary behaviour influence insulin resistance to a greater extent in Chilean Mapuches than Chileans of European descent. These findings have implications for the design and implementation of lifestyle strategies to reduce metabolic risk in different ethnic groups, and for understanding of the mechanisms underpinning human insulin resistance.
Entry, Descent, and Landing technological barriers and crewed MARS vehicle performance analysis
Subrahmanyam, Prabhakar; Rasky, Daniel
2017-05-01
Mars has been explored historically only by robotic crafts, but a crewed mission encompasses several new engineering challenges - high ballistic coefficient entry, hypersonic decelerators, guided entry for reaching intended destinations within acceptable margins for error in the landing ellipse, and payload mass are all critical factors for evaluation. A comprehensive EDL parametric analysis has been conducted in support of a high mass landing architecture by evaluating three types of vehicles -70° Sphere Cone, Ellipsled and SpaceX hybrid architecture called Red Dragon as potential candidate options for crewed entry vehicles. Aerocapture at the Martian orbit of about 400 km and subsequent Entry-from-orbit scenarios were investigated at velocities of 6.75 km/s and 4 km/s respectively. A study on aerocapture corridor over a range of entry velocities (6-9 km/s) suggests that a hypersonic L/D of 0.3 is sufficient for a Martian aerocapture. Parametric studies conducted by varying aeroshell diameters from 10 m to 15 m for several entry masses up to 150 mt are summarized and results reveal that vehicles with entry masses in the range of about 40-80 mt are capable of delivering cargo with a mass on the order of 5-20 mt. For vehicles with an entry mass of 20 mt to 80 mt, probabilistic Monte Carlo analysis of 5000 cases for each vehicle were run to determine the final landing ellipse and to quantify the statistical uncertainties associated with the trajectory and attitude conditions during atmospheric entry. Strategies and current technological challenges for a human rated Entry, Descent, and Landing to the Martian surface are presented in this study.
Ferreira, D V; Von Pinho, R G; Balestre, M; Oliveira, R L
2010-12-14
We evaluated the efficiency of the best linear unbiased predictor (BLUP) and the influence of the use of similarity in state (SIS) and similarity by descent (SBD) in the prediction of untested maize hybrids. Nine inbred lines of maize were crossed using a randomized complete diallel method. These materials were genotyped with 48 microsatellite markers (SSR) associated with the QTL regions for grain yield. Estimates of four coefficients of SIS and four coefficients of SBD were used to construct the additive genetic and dominance matrices, which were later used in combination with the BLUP for predicting genotypic values and specific combining ability (SCA) in unanalyzed hybrids under simulated unbalance. The values of correlations between the genotypic values predicted and the means observed, depending on the degree of unbalance, ranged from 0.48 to 0.99 for SIS and 0.40 to 0.99 using information from SBD. The results obtained for the SCA ranged from 0.26 to 0.98 using the SIS and 0.001 to 0.990 using the SBD information. It was also observed that the predictions using SBD showed less biased than SIS predictions demonstrating that the predictions obtained by these coefficients (SBD) were closer to the observed value, but were less efficient in the ranking of genotypes. Although the SIS showed a bias due to overestimation of relatedness, this type of coefficient may be used where low values are detected in the SBD in the group of parents because of its greater efficiency in ranking the candidates hybrids.
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Carlos A Celis-Morales
Full Text Available BACKGROUND: Effects of urbanisation on diabetes risk appear to be greater in indigenous populations worldwide than in populations of European origin, but the reasons are unclear. This cross-sectional study aimed to determine whether the effects of environment (Rural vs. Urban, adiposity, fitness and lifestyle variables on insulin resistance differed between individuals of indigenous Mapuche origin compared to those of European origin in Chile. METHODOLOGY/PRINCIPAL FINDINGS: 123 Rural Mapuche, 124 Urban Mapuche, 91 Rural European and 134 Urban European Chilean adults had blood taken for determination of HOMA-estimated insulin resistance (HOMA(IR and underwent assessment of physical activity/sedentary behaviour (using accelerometry, cardiorespiratory fitness, dietary intake and body composition. General linear models were used to determine interactions with ethnicity for key variables. There was a significant "ethnicity x environment" interaction for HOMA(IR (Mean±SD; Rural Mapuche: 1.65±2.03, Urban Mapuche: 4.90±3.05, Rural European: 0.82±0.61, Urban European: 1.55±1.34, p((interaction = 0.0003, such that the effect of urbanisation on HOMA(IR was greater in Mapuches than Europeans. In addition, there were significant interactions (all p<0.004 with ethnicity for effects of adiposity, sedentary time and physical activity on HOMA(IR, with greater effects seen in Mapuches compared to Europeans, an observation that persisted after adjustment for potential confounders. CONCLUSIONS/SIGNIFICANCE: Urbanisation, adiposity, physical activity and sedentary behaviour influence insulin resistance to a greater extent in Chilean Mapuches than Chileans of European descent. These findings have implications for the design and implementation of lifestyle strategies to reduce metabolic risk in different ethnic groups, and for understanding of the mechanisms underpinning human insulin resistance.
Directory of Open Access Journals (Sweden)
I. Fer
2008-05-01
Full Text Available Storfjorden in the Svalbard Archipelago is a sill-fjord that produces significant volumes of dense, brine-enriched shelf water through ice formation. The dense water produced in the fjord overflows the sill and can reach deep into the Fram Strait. For conditions corresponding to a moderate ice production year, the pathway of the overflow, its descent and evolving water mass properties due to mixing are investigated for the first time using a high resolution 3-D numerical model. An idealized modeling approach forced by a typical annual cycle of buoyancy forcing due to ice production is chosen in a terrain-following vertical co-ordinate. Comparison with observational data, including hydrography, fine resolution current measurements and direct turbulence measurements using a microstructure profiler, gives confidence on the model performance. The model eddy diffusivity profiles contrasted to those inferred from the turbulence measurements give confidence on the skill of the Mellor Yamada scheme in representing sub-grid scale mixing for the Storfjorden overflow, and probably for gravity current modeling, in general. The Storfjorden overflow is characterized by low Froude number dynamics except at the shelf break where the plume narrows, accelerates with speed reaching 0.6 m s^{−1}, yielding local Froude number in excess of unity. The volume flux of the plume increases by five-fold from the sill to downstream of the shelf-break. Rotational hydraulic control is not applicable for transport estimates at the sill using upstream basin information. To the leading order, geostrophy establishes the lateral slope of the plume interface at the sill. This allows for a transport estimate that is consistent with the model results by evaluating a weir relation at the sill.
Miller, Joyce Catherine
Quantitative and qualitative methodologies were combined to explore the relationships between an understanding of evolution and 4 epistemology factors: (a) control of learning, (b) speed of learning , (c) stability of knowledge, and (d) belief in evolution/creationism. A 17-item instrument was developed that reliably measured a belief in creationism and subtle differences between this belief and an acceptance of evolution. The subjects were 45 students enrolled in a biology course at a 2-year community college. Evolution was taught in a traditional format, and common descent was taught in an inquiry-based laboratory session consisting of: (a) a comparison of hemoglobin DNA sequences of the human, chimpanzee, and gorilla; and (b) a comparison of 8 primate skull casts, including the modern human, chimpanzee, gorilla, and five prehistoric fossils. Prior to instruction the students completed an epistemology questionnaire and a knowledge test about evolution. Five weeks after instruction, the students completed a posttest. A t-test revealed no differences between the pretest and the posttest. However, the group of students that scored higher on the posttest than on the pretest was found to have a stronger belief in the uncertainty of knowledge. Pearson r was computed to check for relationships between the 4 epistemological factors and the understanding of evolution. There was a significant relationship between a belief in creationism and a lessor understanding of evolution as measured on both the pretest and the posttest (ps humans evolved from the chimpanzee. Additionally, students grouped the 8 primate skulls into just 2 categories: human and animals. Other misconceptions included a nonevolutionary use of the term, related, and the use of naive organizers leading to incorrect conclusions about the relatedness of certain organisms, such as a connection between fish and whales. These organizers included: (a) similarity of traits, (b) environment, (c) relative size, (d
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Xun Wu
Full Text Available Maize foundation parents (FPs play no-alternative roles in hybrid breeding because they were widely used in the development of new lines and hybrids. The combination of different identity-by-descent (IBD segments and genes could account for the formation patterns of different FPs, and knowledge of these IBD regions would provide an extensive foundation for the development of new candidate FP lines in future maize breeding. In this paper, a panel of 304 elite lines derived from FPs, i.e., B73, 207, Mo17, and Huangzaosi (HZS, was collected and analyzed using 43,252 single nucleotide polymorphism (SNP markers. Most IBD segments specific to particular FP groups were identified, including 116 IBD segments in B73, 105 in Mo17, 111 in 207, and 190 in HZS. In these regions, 423 quantitative trait nucleotides (QTNs associated with 15 agronomic traits and 804 candidate genes were identified. Some known adaptation-related genes, e.g., dwarf8 and vgt1 in HZS, zcn8 and epc in Mo17, and ZmCCT in 207, were validated as being tightly linked to particular IBD segments. In addition, numerous new candidate genes were also identified. For example, GRMZM2G154278 in HZS, which belongs to the cell cycle control family, was closely linked to a QTN of the ear height/plant height (EH/PH trait; GRMZM2G051943 in 207, which encodes an endochitinase precursor (EP chitinase, was closely linked to a QTN for kernel density; and GRMZM2G170586 in Mo17 was closely linked to a QTN for ear diameter. Complex correlations among these genes were also found. Many IBD segments and genes were included in the formation of FP lines, and complex regulatory networks exist among them. These results provide new insights on the genetic basis of complex traits and provide new candidate IBD regions or genes for the improvement of special traits in maize production.
Acculturation, maternal cortisol, and birth outcomes in women of Mexican descent.
D'Anna-Hernandez, Kimberly L; Hoffman, Maria Camille; Zerbe, Gary O; Coussons-Read, Mary; Ross, Randal G; Laudenslager, Mark L
2012-04-01
This study investigated the effects of acculturation on cortisol, a biological correlate of maternal psychological distress, and perinatal infant outcomes, specifically gestational age at birth and birth weight. Fifty-five pregnant women of Mexican descent were recruited from a community hospital, and their saliva samples were collected at home for 3 days during pregnancy at 15 to 18 weeks (early), 26 to 32 weeks (mid), and more than 32 weeks (late) of gestation and once in the postpartum period (4-12 weeks). These values were used to determine the diurnal cortisol slope at each phase of pregnancy. Mothers also completed an acculturation survey and gave permission for a medical chart review to obtain neonate information. Multiple regression analyses determined that greater acculturation levels significantly predicted earlier infant gestational age at birth (R(2) = 0.09, p = .03). Results from t tests revealed that mothers of low-birth-weight infants (acculturation scores than mothers of infants with birth weight greater than 2500 g (t = -2.95, p = .005). A blunted maternal cortisol slope during pregnancy was also correlated with low birth weight (r = -0.29, p = .05) but not gestational age (r = -0.08, p = .59). In addition, more acculturated women had a flatter diurnal cortisol slope late in pregnancy (R(2) = 0.21, p = .01). Finally, diurnal maternal cortisol rhythms were identified as a potential mediator between increased acculturation and birth weight. This study associated increased acculturation with perinatal outcomes in the US Mexican population. This relationship may be mediated by prenatal maternal diurnal cortisol, which can program the health of the fetus leading to several adverse perinatal outcomes.
Constrained optimization via simulation models for new product innovation
Pujowidianto, Nugroho A.
2017-11-01
We consider the problem of constrained optimization where the decision makers aim to optimize the primary performance measure while constraining the secondary performance measures. This paper provides a brief overview of stochastically constrained optimization via discrete event simulation. Most review papers tend to be methodology-based. This review attempts to be problem-based as decision makers may have already decided on the problem formulation. We consider constrained optimization models as there are usually constraints on secondary performance measures as trade-off in new product development. It starts by laying out different possible methods and the reasons using constrained optimization via simulation models. It is then followed by the review of different simulation optimization approach to address constrained optimization depending on the number of decision variables, the type of constraints, and the risk preferences of the decision makers in handling uncertainties.
Jupiter's evolution with primordial composition gradients
Vazan, A.; Helled, R.; Guillot, T.
2018-01-01
Recent formation and structure models of Jupiter suggest that the planet can have composition gradients and not be fully convective (adiabatic). This possibility directly affects our understanding of Jupiter's bulk composition and origin. In this Letter we present Jupiter's evolution with a primordial structure consisting of a relatively steep heavy-element gradient of 40 Earth masses. We show that for a primordial structure with composition gradients, most of the mixing occurs in the outer p...
Thermal conduction down steep temperature gradients
International Nuclear Information System (INIS)
Bell, A.R.; Evans, R.G.; Nicholas, D.J.
1980-08-01
The Fokker-Planck equation has been solved numerically in one spatial and two velocity dimensions in order to study thermal conduction in large temperature gradients. An initially cold plasma is heated at one end of the spatial grid producing temperature gradients with scale lengths of a few times the electron mean free path. The heat flow is an order of magnitude smaller than that predicted by the classical theory which is valid in the limit of small temperature gradients. (author)
Testing the limits of gradient sensing.
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Vinal Lakhani
2017-02-01
Full Text Available The ability to detect a chemical gradient is fundamental to many cellular processes. In multicellular organisms gradient sensing plays an important role in many physiological processes such as wound healing and development. Unicellular organisms use gradient sensing to move (chemotaxis or grow (chemotropism towards a favorable environment. Some cells are capable of detecting extremely shallow gradients, even in the presence of significant molecular-level noise. For example, yeast have been reported to detect pheromone gradients as shallow as 0.1 nM/μm. Noise reduction mechanisms, such as time-averaging and the internalization of pheromone molecules, have been proposed to explain how yeast cells filter fluctuations and detect shallow gradients. Here, we use a Particle-Based Reaction-Diffusion model of ligand-receptor dynamics to test the effectiveness of these mechanisms and to determine the limits of gradient sensing. In particular, we develop novel simulation methods for establishing chemical gradients that not only allow us to study gradient sensing under steady-state conditions, but also take into account transient effects as the gradient forms. Based on reported measurements of reaction rates, our results indicate neither time-averaging nor receptor endocytosis significantly improves the cell's accuracy in detecting gradients over time scales associated with the initiation of polarized growth. Additionally, our results demonstrate the physical barrier of the cell membrane sharpens chemical gradients across the cell. While our studies are motivated by the mating response of yeast, we believe our results and simulation methods will find applications in many different contexts.
STOCHASTIC GRADIENT METHODS FOR UNCONSTRAINED OPTIMIZATION
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Nataša Krejić
2014-12-01
Full Text Available This papers presents an overview of gradient based methods for minimization of noisy functions. It is assumed that the objective functions is either given with error terms of stochastic nature or given as the mathematical expectation. Such problems arise in the context of simulation based optimization. The focus of this presentation is on the gradient based Stochastic Approximation and Sample Average Approximation methods. The concept of stochastic gradient approximation of the true gradient can be successfully extended to deterministic problems. Methods of this kind are presented for the data fitting and machine learning problems.
Wireless SAW Based Temperature Gradient Sensor Project
National Aeronautics and Space Administration — Prime Photonics proposes design and development of a surface acoustic wave (SAW) based temperature gradient sensor for instrumentation of thermal protection systems...
Community and ecosystem responses to elevational gradients
DEFF Research Database (Denmark)
Sundqvist, Maja K.; Sanders, Nate; Wardle, David A.
2013-01-01
elevational gradients for understanding community and ecosystem responses to global climate change at much larger spatial and temporal scales than is possible through conventional ecological experiments. However, future studies that integrate elevational gradient approaches with experimental manipulations...... will provide powerful information that can improve predictions of climate change impacts within and across ecosystems.......Community structure and ecosystem processes often vary along elevational gradients. Their responses to elevation are commonly driven by changes in temperature, and many community- and ecosystem-level variables therefore frequently respond similarly to elevation across contrasting gradients...
On lower order strain gradient plasticity theories
DEFF Research Database (Denmark)
Niordson, Christian Frithiof; Hutchinson, J. W.
2003-01-01
the tangent moduli governing increments of stress and strain. It is shown that the modification is far from benign from a mathematical standpoint, changing the qualitative character of solutions and leading to a new type of localization that is at odds with what is expected from a strain gradient theory......By way of numerical examples, this paper explores the nature of solutions to a class of strain gradient plasticity theories that employ conventional stresses, equilibrium equations and boundary conditions. Strain gradients come into play in these modified conventional theories only to alter....... The findings raise questions about the physical acceptability of this class of strain gradient theories....
Reflected stochastic differential equation models for constrained animal movement
Hanks, Ephraim M.; Johnson, Devin S.; Hooten, Mevin B.
2017-01-01
Movement for many animal species is constrained in space by barriers such as rivers, shorelines, or impassable cliffs. We develop an approach for modeling animal movement constrained in space by considering a class of constrained stochastic processes, reflected stochastic differential equations. Our approach generalizes existing methods for modeling unconstrained animal movement. We present methods for simulation and inference based on augmenting the constrained movement path with a latent unconstrained path and illustrate this augmentation with a simulation example and an analysis of telemetry data from a Steller sea lion (Eumatopias jubatus) in southeast Alaska.
Resource Management in Constrained Dynamic Situations
Seok, Jinwoo
Resource management is considered in this dissertation for systems with limited resources, possibly combined with other system constraints, in unpredictably dynamic environments. Resources may represent fuel, power, capabilities, energy, and so on. Resource management is important for many practical systems; usually, resources are limited, and their use must be optimized. Furthermore, systems are often constrained, and constraints must be satisfied for safe operation. Simplistic resource management can result in poor use of resources and failure of the system. Furthermore, many real-world situations involve dynamic environments. Many traditional problems are formulated based on the assumptions of given probabilities or perfect knowledge of future events. However, in many cases, the future is completely unknown, and information on or probabilities about future events are not available. In other words, we operate in unpredictably dynamic situations. Thus, a method is needed to handle dynamic situations without knowledge of the future, but few formal methods have been developed to address them. Thus, the goal is to design resource management methods for constrained systems, with limited resources, in unpredictably dynamic environments. To this end, resource management is organized hierarchically into two levels: 1) planning, and 2) control. In the planning level, the set of tasks to be performed is scheduled based on limited resources to maximize resource usage in unpredictably dynamic environments. In the control level, the system controller is designed to follow the schedule by considering all the system constraints for safe and efficient operation. Consequently, this dissertation is mainly divided into two parts: 1) planning level design, based on finite state machines, and 2) control level methods, based on model predictive control. We define a recomposable restricted finite state machine to handle limited resource situations and unpredictably dynamic environments
A Gradient Taguchi Method for Engineering Optimization
Hwang, Shun-Fa; Wu, Jen-Chih; He, Rong-Song
2017-10-01
To balance the robustness and the convergence speed of optimization, a novel hybrid algorithm consisting of Taguchi method and the steepest descent method is proposed in this work. Taguchi method using orthogonal arrays could quickly find the optimum combination of the levels of various factors, even when the number of level and/or factor is quite large. This algorithm is applied to the inverse determination of elastic constants of three composite plates by combining numerical method and vibration testing. For these problems, the proposed algorithm could find better elastic constants in less computation cost. Therefore, the proposed algorithm has nice robustness and fast convergence speed as compared to some hybrid genetic algorithms.
Wayner, Peter C., Jr.; Kundan, Akshay; Plawsky, Joel
2014-01-01
The Constrained Vapor Bubble (CVB) is a wickless, grooved heat pipe and we report on a full- scale fluids experiment flown on the International Space Station (ISS). The CVB system consists of a relatively simple setup a quartz cuvette with sharp corners partially filled with either pentane or an ideal mixture of pentane and isohexane as the working fluids. Along with temperature and pressure measurements, the two-dimensional thickness profile of the menisci formed at the corners of the quartz cuvette was determined using the Light Microscopy Module (LMM). Even with the large, millimeter dimensions of the CVB, interfacial forces dominate in these exceedingly small Bond Number systems. The experiments were carried out at various power inputs. Although conceptually simple, the transport processes were found to be very complex with many different regions. At the heated end of the CVB, due to a high temperature gradient, we observed Marangoni flow at some power inputs. This region from the heated end to the central drop region is defined as a Marangoni dominated region. We present a simple analysis based on interfacial phenomena using only measurements from the ISS experiments that lead to a predictive equation for the thickness of the film near the heated end of the CVB. The average pressure gradient for flow in the film is assumed due to the measured capillary pressure at the two ends of the liquid film and that the pressure stress gradient due to cohesion self adjusts to a constant value over a distance L. The boundary conditions are the no slip condition at the wall interface and an interfacial shear stress at the liquid- vapor interface due to the Marangoni stress, which is due to the high temperature gradient. Although the heated end is extremely complex, since it includes three- dimensional variations in radiation, conduction, evaporation, condensation, fluid flow and interfacial forces, we find that using the above simplifying assumptions, a simple successful
A gradient-based method for segmenting FDG-PET images: methodology and validation
International Nuclear Information System (INIS)
Geets, Xavier; Lee, John A.; Gregoire, Vincent; Bol, Anne; Lonneux, Max
2007-01-01
A new gradient-based method for segmenting FDG-PET images is described and validated. The proposed method relies on the watershed transform and hierarchical cluster analysis. To allow a better estimation of the gradient intensity, iteratively reconstructed images were first denoised and deblurred with an edge-preserving filter and a constrained iterative deconvolution algorithm. Validation was first performed on computer-generated 3D phantoms containing spheres, then on a real cylindrical Lucite phantom containing spheres of different volumes ranging from 2.1 to 92.9 ml. Moreover, laryngeal tumours from seven patients were segmented on PET images acquired before laryngectomy by the gradient-based method and the thresholding method based on the source-to-background ratio developed by Daisne (Radiother Oncol 2003;69:247-50). For the spheres, the calculated volumes and radii were compared with the known values; for laryngeal tumours, the volumes were compared with the macroscopic specimens. Volume mismatches were also analysed. On computer-generated phantoms, the deconvolution algorithm decreased the mis-estimate of volumes and radii. For the Lucite phantom, the gradient-based method led to a slight underestimation of sphere volumes (by 10-20%), corresponding to negligible radius differences (0.5-1.1 mm); for laryngeal tumours, the segmented volumes by the gradient-based method agreed with those delineated on the macroscopic specimens, whereas the threshold-based method overestimated the true volume by 68% (p = 0.014). Lastly, macroscopic laryngeal specimens were totally encompassed by neither the threshold-based nor the gradient-based volumes. The gradient-based segmentation method applied on denoised and deblurred images proved to be more accurate than the source-to-background ratio method. (orig.)
A new modification of Hestenes-Stiefel method with descent properties
Shapiee, Norrlaili; Rivaie, Mohd; Mamat, Mustafa; Mohd, Ismail
2014-06-01
Conjugate gradient (CG) methods are important for large-scale unconstrained optimization due to its low memory requirements and global convergence properties. Numerous researches has been done to proposed new CG coefficients and to improve the efficiency. In this paper, we proposed a new CG coefficient based on the original Hestenes-Steifel CG coefficient. The global convergence result is established using exact line search. Most of our numerical results show that our method is very efficient when compared to the early CG coefficients for a given standard test problems.
Csiba, Dominik
2017-09-09
In this paper we introduce two novel generalizations of the theory for gradient descent type methods in the proximal setting. First, we introduce the proportion function, which we further use to analyze all known (and many new) block-selection rules for block coordinate descent methods under a single framework. This framework includes randomized methods with uniform, non-uniform or even adaptive sampling strategies, as well as deterministic methods with batch, greedy or cyclic selection rules. Second, the theory of strongly-convex optimization was recently generalized to a specific class of non-convex functions satisfying the so-called Polyak-{\\\\L}ojasiewicz condition. To mirror this generalization in the weakly convex case, we introduce the Weak Polyak-{\\\\L}ojasiewicz condition, using which we give global convergence guarantees for a class of non-convex functions previously not considered in theory. Additionally, we establish (necessarily somewhat weaker) convergence guarantees for an even larger class of non-convex functions satisfying a certain smoothness assumption only. By combining the two abovementioned generalizations we recover the state-of-the-art convergence guarantees for a large class of previously known methods and setups as special cases of our general framework. Moreover, our frameworks allows for the derivation of new guarantees for many new combinations of methods and setups, as well as a large class of novel non-convex objectives. The flexibility of our approach offers a lot of potential for future research, as a new block selection procedure will have a convergence guarantee for all objectives considered in our framework, while a new objective analyzed under our approach will have a whole fleet of block selection rules with convergence guarantees readily available.
DEFF Research Database (Denmark)
Khan, Amir; Connolly, J.A.D.; Olsen, Nils
2006-01-01
We reexamine the problem of inverting C responses, covering periods between 1 month and 1 year collected from 42 European observatories, to constrain the internal structure of the Earth. Earlier studies used the C responses, which connect the magnetic vertical component and the horizontal gradient...... of the horizontal components of electromagnetic variations, to obtain the conductivity profile of the Earth's mantle. Here, we go beyond this approach by inverting directly for chemical composition and thermal state of the Earth, rather than subsurface electrical conductivity structure. The primary inversion...... Earth electrical conductivity structure from which C responses are calculated. To further constrain the radial density profile, we also invert for mass and moment of inertia. The results agree with earlier geophysically derived conductivity and seismic velocity models and confirm that inversion...
Constrained Supersymmetric Flipped SU(5) GUT Phenomenology
Ellis, John; Olive, Keith A
2011-01-01
We explore the phenomenology of the minimal supersymmetric flipped SU(5) GUT model (CFSU(5)), whose soft supersymmetry-breaking (SSB) mass parameters are constrained to be universal at some input scale, $M_{in}$, above the GUT scale, $M_{GUT}$. We analyze the parameter space of CFSU(5) assuming that the lightest supersymmetric particle (LSP) provides the cosmological cold dark matter, paying careful attention to the matching of parameters at the GUT scale. We first display some specific examples of the evolutions of the SSB parameters that exhibit some generic features. Specifically, we note that the relationship between the masses of the lightest neutralino and the lighter stau is sensitive to $M_{in}$, as is the relationship between the neutralino mass and the masses of the heavier Higgs bosons. For these reasons, prominent features in generic $(m_{1/2}, m_0)$ planes such as coannihilation strips and rapid-annihilation funnels are also sensitive to $M_{in}$, as we illustrate for several cases with tan(beta)...
Acoustic characteristics of listener-constrained speech
Ashby, Simone; Cummins, Fred
2003-04-01
Relatively little is known about the acoustical modifications speakers employ to meet the various constraints-auditory, linguistic and otherwise-of their listeners. Similarly, the manner by which perceived listener constraints interact with speakers' adoption of specialized speech registers is poorly Hypo (H&H) theory offers a framework for examining the relationship between speech production and output-oriented goals for communication, suggesting that under certain circumstances speakers may attempt to minimize phonetic ambiguity by employing a ``hyperarticulated'' speaking style (Lindblom, 1990). It remains unclear, however, what the acoustic correlates of hyperarticulated speech are, and how, if at all, we might expect phonetic properties to change respective to different listener-constrained conditions. This paper is part of a preliminary investigation concerned with comparing the prosodic characteristics of speech produced across a range of listener constraints. Analyses are drawn from a corpus of read hyperarticulated speech data comprising eight adult, female speakers of English. Specialized registers include speech to foreigners, infant-directed speech, speech produced under noisy conditions, and human-machine interaction. The authors gratefully acknowledge financial support of the Irish Higher Education Authority, allocated to Fred Cummins for collaborative work with Media Lab Europe.
Constraining Amazonian Methane Emission from Wetlands
Boesch, Hartmut; Parker, Robert; Webb, Alex; Wilson, Chris; Chipperfield, Martyn; Gloor, Emanuel; Feng, Liang; Palmer, Paul
2017-04-01
The Amazon Basin contains large wetland ecosystems which are important sources of methane (CH4). Spaceborne observations provide detailed information about the spatio-temporal distributions of atmospheric methane over the Amazon Basin which will provide a strong constrain on the underlying emissions and their year to year variations. Methane observations from space are available from the Japanese GOSAT instrument since 2009. We use the proxy retrieval method which provides much greater coverage over the Amazon region compared to so-called Full-Physics methods due to their lower sensitivity to thin clouds. Validation of GOSAT retrieval over the Amazon using the ground-based TCCON network is currently not possible due to a lack of data and we have used routine aircraft profiles to show that GOSAT columns are sufficiently accurate for estimating surface flux for the region. Using a variational flux inverse system together with the 3-D atmospheric chemical transport model TOMCAT, we infer surface fluxes for the Amazon region from GOSAT observations which are used to analyse the spatial distribution of methane wetlands emissions as well as annual variations in emissions with a focus on periods 2011/2012 and 2013/14 which are characterized by large variations in rainfall.
Constrained Graph Optimization: Interdiction and Preservation Problems
Energy Technology Data Exchange (ETDEWEB)
Schild, Aaron V [Los Alamos National Laboratory
2012-07-30
The maximum flow, shortest path, and maximum matching problems are a set of basic graph problems that are critical in theoretical computer science and applications. Constrained graph optimization, a variation of these basic graph problems involving modification of the underlying graph, is equally important but sometimes significantly harder. In particular, one can explore these optimization problems with additional cost constraints. In the preservation case, the optimizer has a budget to preserve vertices or edges of a graph, preventing them from being deleted. The optimizer wants to find the best set of preserved edges/vertices in which the cost constraints are satisfied and the basic graph problems are optimized. For example, in shortest path preservation, the optimizer wants to find a set of edges/vertices within which the shortest path between two predetermined points is smallest. In interdiction problems, one deletes vertices or edges from the graph with a particular cost in order to impede the basic graph problems as much as possible (for example, delete edges/vertices to maximize the shortest path between two predetermined vertices). Applications of preservation problems include optimal road maintenance, power grid maintenance, and job scheduling, while interdiction problems are related to drug trafficking prevention, network stability assessment, and counterterrorism. Computational hardness results are presented, along with heuristic methods for approximating solutions to the matching interdiction problem. Also, efficient algorithms are presented for special cases of graphs, including on planar graphs. The graphs in many of the listed applications are planar, so these algorithms have important practical implications.
Optimization of input-constrained systems
Malki, Suleyman; Spaanenburg, Lambert
2009-05-01
The computational demands of algorithms are rapidly growing. The naive implementation uses extended doubleprecision floating-point numbers and has therefore extreme difficulties in maintaining real-time performance. For fixedpoint numbers, the value representation pushes in two directions (value range and step size) to set the applicationdependent word size. In the general case, checking all combinations of all different values on all system inputs will easily become computationally infeasible. Checking corner cases only helps to reduce the combinatorial explosion, as still checking for accuracy and precision to limit word size remains a considerable effort. A range of evolutionary techniques have been tried where the sheer size of the problem withstands an extensive search. When the value range can be limited, the problem becomes tractable and a constructive approach becomes feasible. We propose an approach that is reminiscent of the Quine-Mc.Cluskey logic minimization procedure. Next to the conjunctive search as popular in Boolean minimization, we investigate the disjunctive approach that starts from a presumed minimal word size. To eliminate the occurrence of anomalies, this still has to be checked for larger word sizes. The procedure has initially been implemented using Java and Matlab. We have applied the above procedure to feed-forward and to cellular neural networks (CNN) as typical examples of input-constrained systems. In the case of hole-filling by means of a CNN, we find that the 1461 different coefficient sets can be reduced to 360, each giving robust behaviour on 7-bits internal words.
Technologies for a greenhouse-constrained society
International Nuclear Information System (INIS)
Kuliasha, M.A.; Zucker, A.; Ballew, K.J.
1992-01-01
This conference explored how three technologies might help society adjust to life in a greenhouse-constrained environment. Technology experts and policy makers from around the world met June 11--13, 1991, in Oak Ridge, Tennessee, to address questions about how energy efficiency, biomass, and nuclear technologies can mitigate the greenhouse effect and to explore energy production and use in countries in various stages of development. The conference was organized by Oak Ridge National Laboratory and sponsored by the US Department of Energy. Energy efficiency biomass, and nuclear energy are potential substitutes for fossil fuels that might help slow or even reverse the global warming changes that may result from mankind's thirst for energy. Many other conferences have questioned whether the greenhouse effect is real and what reductions in greenhouse gas emissions might be necessary to avoid serious ecological consequences; this conference studied how these reductions might actually be achieved. For these conference proceedings, individuals papers are processed separately for the Energy Data Base
Constraining the roughness degree of slip heterogeneity
Causse, Mathieu
2010-05-07
This article investigates different approaches for assessing the degree of roughness of the slip distribution of future earthquakes. First, we analyze a database of slip images extracted from a suite of 152 finite-source rupture models from 80 events (Mw = 4.1–8.9). This results in an empirical model defining the distribution of the slip spectrum corner wave numbers (kc) as a function of moment magnitude. To reduce the “epistemic” uncertainty, we select a single slip model per event and screen out poorly resolved models. The number of remaining models (30) is thus rather small. In addition, the robustness of the empirical model rests on a reliable estimation of kc by kinematic inversion methods. We address this issue by performing tests on synthetic data with a frequency domain inversion method. These tests reveal that due to smoothing constraints used to stabilize the inversion process, kc tends to be underestimated. We then develop an alternative approach: (1) we establish a proportionality relationship between kc and the peak ground acceleration (PGA), using a k−2 kinematic source model, and (2) we analyze the PGA distribution, which is believed to be better constrained than slip images. These two methods reveal that kc follows a lognormal distribution, with similar standard deviations for both methods.
Constraining the oblateness of Kepler planets
Energy Technology Data Exchange (ETDEWEB)
Zhu, Wei [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Huang, Chelsea X. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Zhou, George [Research School of Astronomy and Astrophysics, Australian National University, Cotter Road, Weston Creek, ACT 2611 (Australia); Lin, D. N. C., E-mail: weizhu@astronomy.ohio-state.edu [UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
2014-11-20
We use Kepler short-cadence light curves to constrain the oblateness of planet candidates in the Kepler sample. The transits of rapidly rotating planets that are deformed in shape will lead to distortions in the ingress and egress of their light curves. We report the first tentative detection of an oblate planet outside the solar system, measuring an oblateness of 0.22{sub −0.11}{sup +0.11} for the 18 M{sub J} mass brown dwarf Kepler 39b (KOI 423.01). We also provide constraints on the oblateness of the planets (candidates) HAT-P-7b, KOI 686.01, and KOI 197.01 to be <0.067, <0.251, and <0.186, respectively. Using the Q' values from Jupiter and Saturn, we expect tidal synchronization for the spins of HAT-P-7b, KOI 686.01, and KOI 197.01, and for their rotational oblateness signatures to be undetectable in the current data. The potentially large oblateness of KOI 423.01 (Kepler 39b) suggests that the Q' value of the brown dwarf needs to be two orders of magnitude larger than that of the solar system gas giants to avoid being tidally spun down.
Canonical trivialization of gravitational gradients
International Nuclear Information System (INIS)
Niedermaier, Max
2017-01-01
A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein–Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie–Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions. (paper)
Canonical trivialization of gravitational gradients
Niedermaier, Max
2017-06-01
A one-parameter family of canonical transformations is constructed that reduces the Hamiltonian form of the Einstein-Hilbert action to its strong coupling limit where dynamical spatial gradients are absent. The parameter can alternatively be viewed as the overall scale of the spatial metric or as a fractional inverse power of Newton’s constant. The generating function of the canonical transformation is constructed iteratively as a powerseries in the parameter to all orders. The algorithm draws on Lie-Deprit transformation theory and defines a ‘trivialization map’ with several bonus properties: (i) Trivialization of the Hamiltonian constraint implies that of the action while the diffeomorphism constraint is automatically co-transformed. (ii) Only a set of ordinary differential equations needs to be solved to drive the iteration via a homological equation where no gauge fixing is required. (iii) In contrast to (the classical limit of) a Lagrangian trivialization map the algorithm also produces series solutions of the field equations. (iv) In the strong coupling theory temporal gauge variations are abelian, nevertheless the map intertwines with the respective gauge symmetries on the action, the field equations, and their solutions.
The single-breath diffusing capacity of CO and NO in healthy children of European descent.
Thomas, Astrid; Hanel, Birgitte; Marott, Jacob L; Buchvald, Frederik; Mortensen, Jann; Nielsen, Kim G
2014-01-01
The diffusing capacity (DL) of the lung can be divided into two components: the diffusing capacity of the alveolar membrane (Dm) and the pulmonary capillary volume (Vc). DL is traditionally measured using a single-breath method, involving inhalation of carbon monoxide, and a breath hold of 8-10 seconds (DL,CO). This method does not easily allow calculation of Dm and Vc. An alternative single-breath method (DL,CO,NO), involving simultaneous inhalation of carbon monoxide and nitric oxide, and traditionally a shorter breath hold, allows calculation of Dm and Vc and the DL,NO/DL,CO ratio in a single respiratory maneuver. The clinical utility of Dm, Vc, and DL,NO/DL,CO in the pediatric age range is currently unknown but also restricted by lack of reference values. The aim of this study was to establish reference ranges for the outcomes of DL,CO,NO with a 5 second breath hold, including the calculated outcomes Dm, Vc, and the DL,NO/DL,CO ratio, as well as to establish reference values for the outcomes of the traditional DL,CO method, with a 10 second breath hold in children. DL,CO,NO and DL,CO were measured in healthy children, of European descent, aged 5-17 years using a Jaeger Masterscreen PFT. The data were analyzed using the Generalized Additive Models for Location Scale and Shape (GAMLSS) statistical method. A total of 326 children were eligible for diffusing capacity measurements, resulting in 312 measurements of DL,CO,NO and 297 of DL,CO, respectively. Reference equations were established for the outcomes of DL,CO,NO and DL,CO, including the calculated values: Vc, Dm, and the DL,NO/DL,CO ratio. These reference values are based on the largest sample of children to date and may provide a basis for future studies of their clinical utility in differentiating between alterations in the pulmonary circulation and changes in the alveolar membrane in pediatric patients.
The single-breath diffusing capacity of CO and NO in healthy children of European descent.
Directory of Open Access Journals (Sweden)
Astrid Thomas
Full Text Available The diffusing capacity (DL of the lung can be divided into two components: the diffusing capacity of the alveolar membrane (Dm and the pulmonary capillary volume (Vc. DL is traditionally measured using a single-breath method, involving inhalation of carbon monoxide, and a breath hold of 8-10 seconds (DL,CO. This method does not easily allow calculation of Dm and Vc. An alternative single-breath method (DL,CO,NO, involving simultaneous inhalation of carbon monoxide and nitric oxide, and traditionally a shorter breath hold, allows calculation of Dm and Vc and the DL,NO/DL,CO ratio in a single respiratory maneuver. The clinical utility of Dm, Vc, and DL,NO/DL,CO in the pediatric age range is currently unknown but also restricted by lack of reference values.The aim of this study was to establish reference ranges for the outcomes of DL,CO,NO with a 5 second breath hold, including the calculated outcomes Dm, Vc, and the DL,NO/DL,CO ratio, as well as to establish reference values for the outcomes of the traditional DL,CO method, with a 10 second breath hold in children.DL,CO,NO and DL,CO were measured in healthy children, of European descent, aged 5-17 years using a Jaeger Masterscreen PFT. The data were analyzed using the Generalized Additive Models for Location Scale and Shape (GAMLSS statistical method.A total of 326 children were eligible for diffusing capacity measurements, resulting in 312 measurements of DL,CO,NO and 297 of DL,CO, respectively. Reference equations were established for the outcomes of DL,CO,NO and DL,CO, including the calculated values: Vc, Dm, and the DL,NO/DL,CO ratio.These reference values are based on the largest sample of children to date and may provide a basis for future studies of their clinical utility in differentiating between alterations in the pulmonary circulation and changes in the alveolar membrane in pediatric patients.
Recurrent TP53 missense mutation in cancer patients of Arab descent.
Zick, Aviad; Kadouri, Luna; Cohen, Sherri; Frohlinger, Michael; Hamburger, Tamar; Zvi, Naama; Plaser, Morasha; Avital, Eilat; Breuier, Shani; Elian, Firase; Salah, Azzam; Goldberg, Yael; Peretz, Tamar
2017-04-01
Hereditary cancer comprises more than 10% of all breast cancer cases. Identification of germinal mutations enables the initiation of a preventive program that can include early detection or preventive treatment and may also have a major impact on cancer therapy. Several recurrent mutations were identified in the BRCA1/2 genes in Jewish populations however, in other ethnic groups in Israel, no recurrent mutations were identified to date. Our group established panel sequencing in cancer patients to identify recurrent, founder, and new mutations in the heterogeneous and diverse populations in Israel, We evaluated five breast cancer patients of Arab descent diagnosed with cancer before the age of 50 years and identified the previously described TP53 mutation, c.541C>T, R181C (rs587782596), in two women from unrelated Arab families. The two probands were diagnosed with breast cancer at a young age (27 and 34 years) and had significant family history spanning a wide range of tumors (breast cancer (BC), papillary thyroid cancer, glioblastoma multiform (GBM), colon cancer and leukemia). The R181C variant is expected to disrupt p53 at the ASPP2 binding domain but not the DNA binding domain and is defined by Clinvar as likely pathogenic and in HGMD as disease mutation. We further tested 85 unrelated Arab cancer patients and father of a BC carrier patient for TP53 c.541C>T using a real time polymerase chain reaction (RT-PCR) approach and identified four additional carriers, two with BC one with lung cancer, and the father of a BC carrier patient, diagnosed with GBM. Another carrier suffering from BC was identified using a Myriad panel, suggesting a recurrent mutation in this population with a frequency of 5/42 (11.9%) of our selected BC patients. We suggest testing Arab women with a breast cancer at a young age, Arab patients with multiple malignancies, or with suggestive family history for TP53 c.541C>T.
Yeh, Connie Y; Goldstein, Orly; Kukekova, Anna V; Holley, Debbie; Knollinger, Amy M; Huson, Heather J; Pearce-Kelling, Susan E; Acland, Gregory M; Komáromy, András M
2013-04-20
Achromatopsia is an autosomal recessive disease characterized by the loss of cone photoreceptor function that results in day-blindness, total colorblindness, and decreased central visual acuity. The most common causes for the disease are mutations in the CNGB3 gene, coding for the beta subunit of the cyclic nucleotide-gated channels in cones. CNGB3-achromatopsia, or cone degeneration (cd), is also known to occur in two canine breeds, the Alaskan malamute (AM) and the German shorthaired pointer. Here we report an in-depth characterization of the achromatopsia phenotype in a new canine breed, the miniature Australian shepherd (MAS). Genotyping revealed that the dog was homozygous for a complete genomic deletion of the CNGB3 gene, as has been previously observed in the AM. Identical breakpoints on chromosome 29 were identified in both the affected AM and MAS with a resulting deletion of 404,820 bp. Pooled DNA samples of unrelated purebred Australian shepherd, MAS, Siberian husky, Samoyed and Alaskan sled dogs were screened for the presence of the affected allele; one Siberian husky and three Alaskan sled dogs were identified as carriers. The affected chromosomes from the AM, MAS, and Siberian husky were genotyped for 147 SNPs in a 3.93 Mb interval within the cd locus. An identical shared affected haplotype, 0.5 Mb long, was observed in all three breeds and defined the minimal linkage disequilibrium (LD) across breeds. This supports the idea that the mutated allele was identical by descent (IBD). We report the occurrence of CNGB3-achromatopsia in a new canine breed, the MAS. The CNGB3-deletion allele previously described in the AM was also observed in a homozygous state in the affected MAS, as well as in a heterozygous carrier state in a Siberian husky and Alaskan sled dogs. All affected alleles were shown to be IBD, strongly suggesting an affected founder effect. Since the MAS is not known to be genetically related to the AM, other breeds may potentially carry the
Custom genotyping for substance addiction susceptibility genes in Jordanians of Arab descent
Directory of Open Access Journals (Sweden)
AL-Eitan Laith N
2012-09-01
Full Text Available Abstract Background Both environmental and genetic factors contribute to individual susceptibility to initiation of substance use and vulnerability to addiction. Determining genetic risk factors can make an important contribution to understanding the processes leading to addiction. In order to identify gene(s and mechanisms associated with substance addiction, a custom platform array search for a genetic association in a case/control of homogenous Jordanian Arab population was undertaken. Patients meeting the DSM-VI criteria for substance dependence (n = 220 and entering eight week treatment program at two Jordanian Drug Rehabilitation Centres were genotyped. In addition, 240 healthy controls were also genotyped. The sequenom MassARRAY system (iPLEX GOLD was used to genotype 49 single nucleotide polymorphisms (SNPs within 8 genes (DRD1, DRD2, DRD3, DRD4, DRD5, BDNF, SLC6A3 and COMT. Results This study revealed six new associations involving SNPs within DRD2 gene on chromosome 11. These six SNPs within the DRD2 were found to be most strongly associated with substance addiction in the Jordanian Arabic sample. The strongest statistical evidence for these new association signals were from rs1799732 in the C/−C promoter and rs1125394 in A/G intron 1 regions of DRD2, with the overall estimate of effects returning an odds ratio of 3.37 (χ2 (2, N = 460 = 21, p-value = 0.000026 and 1.78 (χ2 (2, N = 460 = 8, p-value = 0.001, respectively. It has been suggested that DRD2, dopamine receptor D2, plays an important role in dopamine secretion and the signal pathways of dopaminergic reward and drug addiction. Conclusion This study is the first to show a genetic link to substance addiction in a Jordanian population of Arab descent. These findings may contribute to our understanding of drug addiction mechanisms in Middle Eastern populations and how to manage or dictate therapy for individuals. Comparative analysis with different
Full cyclic coordinate descent: solving the protein loop closure problem in Cα space
Directory of Open Access Journals (Sweden)
Hamelryck Thomas
2005-06-01
Full Text Available Abstract Background Various forms of the so-called loop closure problem are crucial to protein structure prediction methods. Given an N- and a C-terminal end, the problem consists of finding a suitable segment of a certain length that bridges the ends seamlessly. In homology modelling, the problem arises in predicting loop regions. In de novo protein structure prediction, the problem is encountered when implementing local moves for Markov Chain Monte Carlo simulations. Most loop closure algorithms keep the bond angles fixed or semi-fixed, and only vary the dihedral angles. This is appropriate for a full-atom protein backbone, since the bond angles can be considered as fixed, while the (φ, ψ dihedral angles are variable. However, many de novo structure prediction methods use protein models that only consist of Cα atoms, or otherwise do not make use of all backbone atoms. These methods require a method that alters both bond and dihedral angles, since the pseudo bond angle between three consecutive Cα atoms also varies considerably. Results Here we present a method that solves the loop closure problem for Cα only protein models. We developed a variant of Cyclic Coordinate Descent (CCD, an inverse kinematics method from the field of robotics, which was recently applied to the loop closure problem. Since the method alters both bond and dihedral angles, which is equivalent to applying a full rotation matrix, we call our method Full CCD (FCDD. FCCD replaces CCD's vector-based optimization of a rotation around an axis with a singular value decomposition-based optimization of a general rotation matrix. The method is easy to implement and numerically stable. Conclusion We tested the method's performance on sets of random protein Cα segments between 5 and 30 amino acids long, and a number of loops of length 4, 8 and 12. FCCD is fast, has a high success rate and readily generates conformations close to those of real loops. The presence of constraints
Gradient Flow Convolutive Blind Source Separation
DEFF Research Database (Denmark)
Pedersen, Michael Syskind; Nielsen, Chinton Møller
2004-01-01
Experiments have shown that the performance of instantaneous gradient flow beamforming by Cauwenberghs et al. is reduced significantly in reverberant conditions. By expanding the gradient flow principle to convolutive mixtures, separation in a reverberant environment is possible. By use of a circ...
Microinstabilities in weak density gradient tokamak systems
International Nuclear Information System (INIS)
Tang, W.M.; Rewoldt, G.; Chen, L.
1986-04-01
A prominent characteristic of auxiliary-heated tokamak discharges which exhibit improved (''H-mode type'') confinement properties is that their density profiles tend to be much flatter over most of the plasma radius. Depsite this favorable trend, it is emphasized here that, even in the limit of zero density gradient, low-frequency microinstabilities can persist due to the nonzero temperature gradient
Preconditioning the modified conjugate gradient method ...
African Journals Online (AJOL)
In this paper, the convergence analysis of the conventional conjugate Gradient method was reviewed. And the convergence analysis of the modified conjugate Gradient method was analysed with our extension on preconditioning the algorithm. Convergence of the algorithm is a function of the condition number of M-1A.
40 CFR 230.25 - Salinity gradients.
2010-07-01
... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Salinity gradients. 230.25 Section 230.25 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) OCEAN DUMPING SECTION 404(b... Physical and Chemical Characteristics of the Aquatic Ecosystem § 230.25 Salinity gradients. (a) Salinity...
Marko Gómez-Hernández; Guadalupe Williams-Linera; Roger Guevara; D. Jean Lodge
2012-01-01
Gradient analysis is rarely used in studies of fungal communities. Data on macromycetes from eight sites along an elevation gradient in central Veracruz, Mexico, were used to demonstrate methods for gradient analysis that can be applied to studies of communities of fungi. Selected sites from 100 to 3,500 m altitude represent tropical dry forest, tropical montane cloud...
Energy Technology Data Exchange (ETDEWEB)
Ren, Y; Mazzucato, E; Guttenfelder, W; Bell, R E; Domier, C W; LeBlanc, B P; Lee, K C; Luhmann Jr, N C; Smith, D R
2011-03-21
In this letter we report the first clear experimental observation of density gradient stabilization of electron temperature gradient driven turbulence in a fusion plasma. It is observed that longer wavelength modes, k⊥ρs ≤10, are most stabilized by density gradient, and the stabilization is accompanied by about a factor of two decrease in the plasma effective thermal diffusivity.
Security constrained optimal power flow by modern optimization tools
African Journals Online (AJOL)
Security constrained optimal power flow by modern optimization tools. ... International Journal of Engineering, Science and Technology ... This problem is represented as a two stage, security constrained OPF problem, in which the first stage optimizes the problem using a genetic algorithm for the purpose of comparison, ...
21 CFR 888.3720 - Toe joint polymer constrained prosthesis.
2010-04-01
... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Toe joint polymer constrained prosthesis. 888.3720 Section 888.3720 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... prosthesis. (a) Identification. A toe joint polymer constrained prosthesis is a device made of silicone...
I/O-Efficient Construction of Constrained Delaunay Triangulations
DEFF Research Database (Denmark)
Agarwal, Pankaj Kumar; Arge, Lars; Yi, Ke
2005-01-01
In this paper, we designed and implemented an I/O-efficient algorithm for constructing constrained Delaunay triangulations. If the number of constraining segments is smaller than the memory size, our algorithm runs in expected O( N B logM/B NB ) I/Os for triangulating N points in the plane, where...
The Pendulum: From Constrained Fall to the Concept of Potential
Bevilacqua, Fabio; Falomo, Lidia; Fregonese, Lucio; Giannetto, Enrico; Giudice, Franco; Mascheretti, Paolo
2006-01-01
Kuhn underlined the relevance of Galileo's gestalt switch in the interpretation of a swinging body from constrained fall to time metre. But the new interpretation did not eliminate the older one. The constrained fall, both in the motion of pendulums and along inclined planes, led Galileo to the law of free fall. Experimenting with physical…
Directory of Open Access Journals (Sweden)
Edward Gilbert-Kawai
2016-08-01
Full Text Available Present knowledge of how the microcirculation is altered by prolonged exposure to hypoxia at high altitude is incomplete and modification of existing analytical techniques may improve our knowledge considerably. We set out to use a novel simplified method of measuring in vivo capillary density during an expedition to high altitude using a CytoCam incident dark field imaging video-microscope. The simplified method of data capture involved recording one-second images of the mucosal surface of the inner lip to reveal data about microvasculature density in ten individuals. This was done on ascent to, and descent from, high altitude. Analysis was conducted offline by two independent investigators blinded to the participant identity, testing conditions and the imaging site. Additionally we monitored haemoglobin concentration and haematocrit data to see if we could support or refute mechanisms of altered density relating to vessel recruitment. Repeated sets of paired values were compared using Kruskall Wallis Analysis of Variance tests, whilst comparisons of values between sites was by related samples Wilcoxon Signed Rank Test. Correlation between different variables was performed using Spearman’s rank correlation coefficient, and concordance between analysing investigators using intra-class correlation coefficient. There was a significant increase in capillary density from London on ascent to high altitude; median capillaries per field of view area increased from 22.8 to 25.3 (p=0.021. There was a further increase in vessel density during the six weeks spent at altitude (25.3 to 32.5, p=0.017. Moreover, vessel density remained high on descent to Kathmandu (31.0 capillaries per field of view area, despite a significant decrease in haemoglobin concentration and haematocrit. Using a simplified technique, we have demonstrated an increase in capillary density on early and sustained exposure to hypobaric hypoxia at thigh altitude, and that this remains
Shieh, Niahn-Chung; Lin, Chun-Liang; Lin, Yu-Chen; Liang, Kuo-Zoo
2005-07-01
This research proposes a systematic and effective optimization process for the design of vertical passive suspension of light rail vehicles (LRVs) using new constrained multiobjective evolution algorithms. A multibody dynamic model of the three-car train set is presented and the suspension spring and damping parameters are optimally designed. A new design of the passive suspension is aided by the use of evolution algorithms to attain the best compromise between ride quality and suspension deflections due to irregular gradient tracks. Extensive simulations are performed to verify the proposed design scheme. The preliminary results show that, when the passive suspension is optimized via the proposed approach, a substantial improvement in the vertical ride quality is obtained while keeping the suspension deflections within their allowable clearance when the light rail vehicle runs onto the worst track condition.
Prevot, Thomas
2012-01-01
This paper describes the underlying principles and algorithms for computing the primary controller managed spacing (CMS) tools developed at NASA for precisely spacing aircraft along efficient descent paths. The trajectory-based CMS tools include slot markers, delay indications and speed advisories. These tools are one of three core NASA technologies integrated in NASAs ATM technology demonstration-1 (ATD-1) that will operationally demonstrate the feasibility of fuel-efficient, high throughput arrival operations using Automatic Dependent Surveillance Broadcast (ADS-B) and ground-based and airborne NASA technologies for precision scheduling and spacing.
Three-dimensional Gravity Inversion with a New Gradient Scheme on Unstructured Grids
Sun, S.; Yin, C.; Gao, X.; Liu, Y.; Zhang, B.
2017-12-01
Stabilized gradient-based methods have been proved to be efficient for inverse problems. Based on these methods, setting gradient close to zero can effectively minimize the objective function. Thus the gradient of objective function determines the inversion results. By analyzing the cause of poor resolution on depth in gradient-based gravity inversion methods, we find that imposing depth weighting functional in conventional gradient can improve the depth resolution to some extent. However, the improvement is affected by the regularization parameter and the effect of the regularization term becomes smaller with increasing depth (shown as Figure 1 (a)). In this paper, we propose a new gradient scheme for gravity inversion by introducing a weighted model vector. The new gradient can improve the depth resolution more efficiently, which is independent of the regularization parameter, and the effect of regularization term will not be weakened when depth increases. Besides, fuzzy c-means clustering method and smooth operator are both used as regularization terms to yield an internal consecutive inverse model with sharp boundaries (Sun and Li, 2015). We have tested our new gradient scheme with unstructured grids on synthetic data to illustrate the effectiveness of the algorithm. Gravity forward modeling with unstructured grids is based on the algorithm proposed by Okbe (1979). We use a linear conjugate gradient inversion scheme to solve the inversion problem. The numerical experiments show a great improvement in depth resolution compared with regular gradient scheme, and the inverse model is compact at all depths (shown as Figure 1 (b)). AcknowledgeThis research is supported by Key Program of National Natural Science Foundation of China (41530320), China Natural Science Foundation for Young Scientists (41404093), and Key National Research Project of China (2016YFC0303100, 2017YFC0601900). ReferencesSun J, Li Y. 2015. Multidomain petrophysically constrained inversion and
Laterally constrained inversion for CSAMT data interpretation
Wang, Ruo; Yin, Changchun; Wang, Miaoyue; Di, Qingyun
2015-10-01
Laterally constrained inversion (LCI) has been successfully applied to the inversion of dc resistivity, TEM and airborne EM data. However, it hasn't been yet applied to the interpretation of controlled-source audio-frequency magnetotelluric (CSAMT) data. In this paper, we apply the LCI method for CSAMT data inversion by preconditioning the Jacobian matrix. We apply a weighting matrix to Jacobian to balance the sensitivity of model parameters, so that the resolution with respect to different model parameters becomes more uniform. Numerical experiments confirm that this can improve the convergence of the inversion. We first invert a synthetic dataset with and without noise to investigate the effect of LCI applications to CSAMT data, for the noise free data, the results show that the LCI method can recover the true model better compared to the traditional single-station inversion; and for the noisy data, the true model is recovered even with a noise level of 8%, indicating that LCI inversions are to some extent noise insensitive. Then, we re-invert two CSAMT datasets collected respectively in a watershed and a coal mine area in Northern China and compare our results with those from previous inversions. The comparison with the previous inversion in a coal mine shows that LCI method delivers smoother layer interfaces that well correlate to seismic data, while comparison with a global searching algorithm of simulated annealing (SA) in a watershed shows that though both methods deliver very similar good results, however, LCI algorithm presented in this paper runs much faster. The inversion results for the coal mine CSAMT survey show that a conductive water-bearing zone that was not revealed by the previous inversions has been identified by the LCI. This further demonstrates that the method presented in this paper works for CSAMT data inversion.
Constraining Cosmic Evolution of Type Ia Supernovae
Energy Technology Data Exchange (ETDEWEB)
Foley, Ryan J.; Filippenko, Alexei V.; Aguilera, C.; Becker, A.C.; Blondin, S.; Challis, P.; Clocchiatti, A.; Covarrubias, R.; Davis, T.M.; Garnavich, P.M.; Jha, S.; Kirshner, R.P.; Krisciunas, K.; Leibundgut, B.; Li, W.; Matheson, T.; Miceli, A.; Miknaitis, G.; Pignata, G.; Rest, A.; Riess, A.G.; /UC, Berkeley, Astron. Dept. /Cerro-Tololo InterAmerican Obs. /Washington U., Seattle, Astron. Dept. /Harvard-Smithsonian Ctr. Astrophys. /Chile U., Catolica /Bohr Inst. /Notre Dame U. /KIPAC, Menlo Park /Texas A-M /European Southern Observ. /NOAO, Tucson /Fermilab /Chile U., Santiago /Harvard U., Phys. Dept. /Baltimore, Space Telescope Sci. /Johns Hopkins U. /Res. Sch. Astron. Astrophys., Weston Creek /Stockholm U. /Hawaii U. /Illinois U., Urbana, Astron. Dept.
2008-02-13
We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 ultraviolet spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with similar slit widths, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be {approx}0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of {approx}3% in the optical and growing toward the ultraviolet. The difference between the maximum-light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.
Regional Responses to Constrained Water Availability
Cui, Y.; Calvin, K. V.; Hejazi, M. I.; Clarke, L.; Kim, S. H.; Patel, P.
2017-12-01
There have been many concerns about water as a constraint to agricultural production, electricity generation, and many other human activities in the coming decades. Nevertheless, how different countries/economies would respond to such constraints has not been explored. Here, we examine the responding mechanism of binding water availability constraints at the water basin level and across a wide range of socioeconomic, climate and energy technology scenarios. Specifically, we look at the change in water withdrawals between energy, land-use and other sectors within an integrated framework, by using the Global Change Assessment Model (GCAM) that also endogenizes water use and allocation decisions based on costs. We find that, when water is taken into account as part of the production decision-making, countries/basins in general fall into three different categories, depending on the change of water withdrawals and water re-allocation between sectors. First, water is not a constraining factor for most of the basins. Second, advancements in water-saving technologies of the electricity generation cooling systems are sufficient of reducing water withdrawals to meet binding water availability constraints, such as in China and the EU-15. Third, water-saving in the electricity sector alone is not sufficient and thus cannot make up the lowered water availability from the binding case; for example, many basins in Pakistan, Middle East and India have to largely reduce irrigated water withdrawals by either switching to rain-fed agriculture or reducing production. The dominant responding strategy for individual countries/basins is quite robust across the range of alternate scenarios that we test. The relative size of water withdrawals between energy and agriculture sectors is one of the most important factors that affect the dominant mechanism.
Constrained information maximization by free energy minimization
Kamimura, Ryotaro
2011-10-01
In this paper we introduce free energy-based methods to constrain mutual information maximization, developed to realize competitive learning. The new method is introduced to simplify the computational procedures of mutual information and to improve the fidelity of representation and to stabilize learning. First, the free energy is effective in simplifying the computation procedures of mutual information because we need not directly compute mutual information, which needs heavy computation, but only deals with partition functions. With partition functions, computational complexity is significantly reduced. Second, fidelity to input patterns can be improved because training errors between input patterns and connection weights are implicitly incorporated. This means that mutual information is maximized under the constraint of the errors between input patterns and connection weights. Finally, learning can be stabilized in our approach. One of the problems of the free energy approach is that learning processes should be carefully controlled to keep its stability. The present paper shows that the conventional computational techniques in the field of self-organizing maps are really effective in controlling the processes. In particular, minimum information production learning can be used further to stabilize learning by decreasing information obtained at each learning step as much as possible. Thus, we can expect that our new method can be used to increase mutual information between competitive units and input patterns without decreasing errors between input patterns and connection weights and with stabilized learning processes. We applied the free energy-based models to the well-known Iris problem and a student survey, and succeeded in improving the performance in terms of classification rates. In addition, the minimum information production learning turned out to be effective in stabilizing learning.
The cost-constrained traveling salesman problem
Energy Technology Data Exchange (ETDEWEB)
Sokkappa, P.R.
1990-10-01
The Cost-Constrained Traveling Salesman Problem (CCTSP) is a variant of the well-known Traveling Salesman Problem (TSP). In the TSP, the goal is to find a tour of a given set of cities such that the total cost of the tour is minimized. In the CCTSP, each city is given a value, and a fixed cost-constraint is specified. The objective is to find a subtour of the cities that achieves maximum value without exceeding the cost-constraint. Thus, unlike the TSP, the CCTSP requires both selection and sequencing. As a consequence, most results for the TSP cannot be extended to the CCTSP. We show that the CCTSP is NP-hard and that no K-approximation algorithm or fully polynomial approximation scheme exists, unless P = NP. We also show that several special cases are polynomially solvable. Algorithms for the CCTSP, which outperform previous methods, are developed in three areas: upper bounding methods, exact algorithms, and heuristics. We found that a bounding strategy based on the knapsack problem performs better, both in speed and in the quality of the bounds, than methods based on the assignment problem. Likewise, we found that a branch-and-bound approach using the knapsack bound was superior to a method based on a common branch-and-bound method for the TSP. In our study of heuristic algorithms, we found that, when selecting modes for inclusion in the subtour, it is important to consider the neighborhood'' of the nodes. A node with low value that brings the subtour near many other nodes may be more desirable than an isolated node of high value. We found two types of repetition to be desirable: repetitions based on randomization in the subtour buildings process, and repetitions encouraging the inclusion of different subsets of the nodes. By varying the number and type of repetitions, we can adjust the computation time required by our method to obtain algorithms that outperform previous methods.
Tune-stabilized, non-scaling, fixed-field, alternating gradient accelerator
Johnstone, Carol J [Warrenville, IL
2011-02-01
A FFAG is a particle accelerator having turning magnets with a linear field gradient for confinement and a large edge angle to compensate for acceleration. FODO cells contain focus magnets and defocus magnets that are specified by a number of parameters. A set of seven equations, called the FFAG equations relate the parameters to one another. A set of constraints, call the FFAG constraints, constrain the FFAG equations. Selecting a few parameters, such as injection momentum, extraction momentum, and drift distance reduces the number of unknown parameters to seven. Seven equations with seven unknowns can be solved to yield the values for all the parameters and to thereby fully specify a FFAG.
Intracellular chemical gradients: morphing principle in bacteria
Directory of Open Access Journals (Sweden)
Endres Robert G
2012-09-01
Full Text Available Abstract Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012 postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development.
Satellite gravity gradient grids for geophysics.
Bouman, Johannes; Ebbing, Jörg; Fuchs, Martin; Sebera, Josef; Lieb, Verena; Szwillus, Wolfgang; Haagmans, Roger; Novak, Pavel
2016-02-11
The Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite aimed at determining the Earth's mean gravity field. GOCE delivered gravity gradients containing directional information, which are complicated to use because of their error characteristics and because they are given in a rotating instrument frame indirectly related to the Earth. We compute gravity gradients in grids at 225 km and 255 km altitude above the reference ellipsoid corresponding to the GOCE nominal and lower orbit phases respectively, and find that the grids may contain additional high-frequency content compared with GOCE-based global models. We discuss the gradient sensitivity for crustal depth slices using a 3D lithospheric model of the North-East Atlantic region, which shows that the depth sensitivity differs from gradient to gradient. In addition, the relative signal power for the individual gradient component changes comparing the 225 km and 255 km grids, implying that using all components at different heights reduces parameter uncertainties in geophysical modelling. Furthermore, since gravity gradients contain complementary information to gravity, we foresee the use of the grids in a wide range of applications from lithospheric modelling to studies on dynamic topography, and glacial isostatic adjustment, to bedrock geometry determination under ice sheets.
Efficient non-negative constrained model-based inversion in optoacoustic tomography
Ding, Lu; Luís Deán-Ben, X.; Lutzweiler, Christian; Razansky, Daniel; Ntziachristos, Vasilis
2015-09-01
The inversion accuracy in optoacoustic tomography depends on a number of parameters, including the number of detectors employed, discrete sampling issues or imperfectness of the forward model. These parameters result in ambiguities on the reconstructed image. A common ambiguity is the appearance of negative values, which have no physical meaning since optical absorption can only be higher or equal than zero. We investigate herein algorithms that impose non-negative constraints in model-based optoacoustic inversion. Several state-of-the-art non-negative constrained algorithms are analyzed. Furthermore, an algorithm based on the conjugate gradient method is introduced in this work. We are particularly interested in investigating whether positive restrictions lead to accurate solutions or drive the appearance of errors and artifacts. It is shown that the computational performance of non-negative constrained inversion is higher for the introduced algorithm than for the other algorithms, while yielding equivalent results. The experimental performance of this inversion procedure is then tested in phantoms and small animals, showing an improvement in image quality and quantitativeness with respect to the unconstrained approach. The study performed validates the use of non-negative constraints for improving image accuracy compared to unconstrained methods, while maintaining computational efficiency.
Viscoelasticity using reactive constrained solid mixtures.
Ateshian, Gerard A
2015-04-13
This study presents a framework for viscoelasticity where the free energy density depends on the stored energy of intact strong and weak bonds, where weak bonds break and reform in response to loading. The stress is evaluated by differentiating the free energy density with respect to the deformation gradient, similar to the conventional approach for hyperelasticity. The breaking and reformation of weak bonds is treated as a reaction governed by the axiom of mass balance, where the constitutive relation for the mass supply governs the bond kinetics. The evolving mass contents of these weak bonds serve as observable state variables. Weak bonds reform in an energy-free and stress-free state, therefore their reference configuration is given by the current configuration at the time of their reformation. A principal advantage of this formulation is the availability of a strain energy density function that depends only on observable state variables, also allowing for a separation of the contributions of strong and weak bonds. The Clausius-Duhem inequality is satisfied by requiring that the net free energy from all breaking bonds must be decreasing at all times. In the limit of infinitesimal strains, linear stress-strain responses and first-order kinetics for breaking and reforming of weak bonds, the reactive framework reduces exactly to classical linear viscoelasticity. For large strains, the reactive and classical quasilinear viscoelasticity theories produce different equations, though responses to standard loading configurations behave similarly. This formulation complements existing tools for modeling the nonlinear viscoelastic response of biological soft tissues under large deformations. Copyright © 2015 Elsevier Ltd. All rights reserved.
Sound beam manipulation based on temperature gradients
Energy Technology Data Exchange (ETDEWEB)
Qian, Feng [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); School of Physics & Electronic Engineering, Changshu Institute of Technology, Changshu 215500 (China); Quan, Li; Liu, Xiaozhou, E-mail: xzliu@nju.edu.cn; Gong, Xiufen [Key Laboratory of Modern Acoustics, Institute of Acoustics and School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)
2015-10-28
Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking.
On fracture in finite strain gradient plasticity
DEFF Research Database (Denmark)
Martínez Pañeda, Emilio; Niordson, Christian Frithiof
2016-01-01
predictions. These differences increase significantly when large strains are taken into account, as a consequence of the contribution of strain gradients to the work hardening of the material. The magnitude of stress elevation at the crack tip and the distance ahead of the crack where GNDs significantly alter......In this work a general framework for damage and fracture assessment including the effect of strain gradients is provided. Both mechanism-based and phenomenological strain gradient plasticity (SGP) theories are implemented numerically using finite deformation theory and crack tip fields...
Speciation gradients and the distribution of biodiversity.
Schluter, Dolph; Pennell, Matthew W
2017-05-31
Global patterns of biodiversity are influenced by spatial and environmental variations in the rate at which new species form. We relate variations in speciation rates to six key patterns of biodiversity worldwide, including the species-area relationship, latitudinal gradients in species and genetic diversity, and between-habitat differences in species richness. Although they sometimes mirror biodiversity patterns, recent rates of speciation, at the tip of the tree of life, are often highest where species richness is low. Speciation gradients therefore shape, but are also shaped by, biodiversity gradients and are often more useful for predicting future patterns of biodiversity than for interpreting the past.
Sound beam manipulation based on temperature gradients
International Nuclear Information System (INIS)
Qian, Feng; Quan, Li; Liu, Xiaozhou; Gong, Xiufen
2015-01-01
Previous research with temperature gradients has shown the feasibility of controlling airborne sound propagation. Here, we present a temperature gradients based airborne sound manipulation schemes: a cylindrical acoustic omnidirectional absorber (AOA). The proposed AOA has high absorption performance which can almost completely absorb the incident wave. Geometric acoustics is used to obtain the refractive index distributions with different radii, which is then utilized to deduce the desired temperature gradients. Since resonant units are not applied in the scheme, its working bandwidth is expected to be broadband. The scheme is temperature-tuned and easy to realize, which is of potential interest to fields such as noise control or acoustic cloaking
Auditory and visual connectivity gradients in frontoparietal cortex.
Braga, Rodrigo M; Hellyer, Peter J; Wise, Richard J S; Leech, Robert
2017-01-01
A frontoparietal network of brain regions is often implicated in both auditory and visual information processing. Although it is possible that the same set of multimodal regions subserves both modalities, there is increasing evidence that there is a differentiation of sensory function within frontoparietal cortex. Magnetic resonance imaging (MRI) in humans was used to investigate whether different frontoparietal regions showed intrinsic biases in connectivity with visual or auditory modalities. Structural connectivity was assessed with diffusion tractography and functional connectivity was tested using functional MRI. A dorsal-ventral gradient of function was observed, where connectivity with visual cortex dominates dorsal frontal and parietal connections, while connectivity with auditory cortex dominates ventral frontal and parietal regions. A gradient was also observed along the posterior-anterior axis, although in opposite directions in prefrontal and parietal cortices. The results suggest that the location of neural activity within frontoparietal cortex may be influenced by these intrinsic biases toward visual and auditory processing. Thus, the location of activity in frontoparietal cortex may be influenced as much by stimulus modality as the cognitive demands of a task. It was concluded that stimulus modality was spatially encoded throughout frontal and parietal cortices, and was speculated that such an arrangement allows for top-down modulation of modality-specific information to occur within higher-order cortex. This could provide a potentially faster and more efficient pathway by which top-down selection between sensory modalities could occur, by constraining modulations to within frontal and parietal regions, rather than long-range connections to sensory cortices. Hum Brain Mapp 38:255-270, 2017. © 2016 Wiley Periodicals, Inc. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.
Trinh, Philippe H.
2016-07-01
The standard analytical approach for studying steady gravity free-surface waves generated by a moving body often relies upon a linearization of the physical geometry, where the body is considered asymptotically small in one or several of its dimensions. In this paper, a methodology that avoids any such geometrical simplification is presented for the case of steady-state flows at low speeds. The approach is made possible through a reduction of the water-wave equations to a complex-valued integral equation that can be studied using the method of steepest descents. The main result is a theory that establishes a correspondence between different bluff-bodied free-surface flow configurations, with the topology of the Riemann surface formed by the steepest descent paths. Then, when a geometrical feature of the body is modified, a corresponding change to the Riemann surface is observed, and the resultant effects to the water waves can be derived. This visual procedure is demonstrated for the case of two-dimensional free-surface flow past a surface-piercing ship and over an angled step in a channel.
Directory of Open Access Journals (Sweden)
Christian Lester D. Gimeno
2017-11-01
Full Text Available –This research study focused on the development of a software that helps students design, write, validate and run their pseudocode in a semi Integrated Development Environment (IDE instead of manually writing it on a piece of paper.Specifically, the study aimed to develop lexical analyzer or lexer, syntax analyzer or parser using recursive descent parsing algorithm and an interpreter. The lexical analyzer reads pseudocodesource in a sequence of symbols or characters as lexemes.The lexemes are then analyzed by the lexer that matches a pattern for valid tokens and passes to the syntax analyzer or parser. The syntax analyzer or parser takes those valid tokens and builds meaningful commands using recursive descent parsing algorithm in a form of an abstract syntax tree. The generation of an abstract syntax tree is based on the specified grammar rule created by the researcher expressed in Extended Backus-Naur Form. The Interpreter takes the generated abstract syntax tree and starts the evaluation or interpretation to produce pseudocode output. The software was evaluated using white-box testing by several ICT professionals and black-box testing by several computer science students based on the International Organization for Standardization (ISO 9126 software quality standards. The overall results of the evaluation both for white-box and black-box were described as “Excellent in terms of functionality, reliability, usability, efficiency, maintainability and portability”.
Directory of Open Access Journals (Sweden)
M. Peng
2017-07-01
Full Text Available The multi-source DEMs generated using the images acquired in the descent and landing phase and after landing contain supplementary information, and this makes it possible and beneficial to produce a higher-quality DEM through fusing the multi-scale DEMs. The proposed fusion method consists of three steps. First, source DEMs are split into small DEM patches, then the DEM patches are classified into a few groups by local density peaks clustering. Next, the grouped DEM patches are used for sub-dictionary learning by stochastic coordinate coding. The trained sub-dictionaries are combined into a dictionary for sparse representation. Finally, the simultaneous orthogonal matching pursuit (SOMP algorithm is used to achieve sparse representation. We use the real DEMs generated from Chang’e-3 descent images and navigation camera (Navcam stereo images to validate the proposed method. Through the experiments, we have reconstructed a seamless DEM with the highest resolution and the largest spatial coverage among the input data. The experimental results demonstrated the feasibility of the proposed method.
Kalman, Lisa; Wilson, Jean Amos; Buller, Arlene; Dixon, John; Edelmann, Lisa; Geller, Louis; Highsmith, William Edward; Holtegaard, Leonard; Kornreich, Ruth; Rohlfs, Elizabeth M; Payeur, Toby L; Sellers, Tina; Toji, Lorraine; Muralidharan, Kasinathan
2009-11-01
Many recessive genetic disorders are found at a higher incidence in people of Ashkenazi Jewish (AJ) descent than in the general population. The American College of Medical Genetics and the American College of Obstetricians and Gynecologists have recommended that individuals of AJ descent undergo carrier screening for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, and Gaucher disease. Although these recommendations have led to increased test volumes and number of laboratories offering AJ screening, well-characterized genomic reference materials are not publicly available. The Centers for Disease Control and Prevention-based Genetic Testing Reference Materials Coordination Program, in collaboration with members of the genetic testing community and Coriell Cell Repositories, have developed a panel of characterized genomic reference materials for AJ genetic testing. DNA from 31 cell lines, representing many of the common alleles for Tay Sachs disease, Canavan disease, familial dysautonomia, mucolipidosis IV, Niemann-Pick disease type A, Fanconi anemia type C, Bloom syndrome, Gaucher disease, and glycogen storage disease, was prepared by the Repository and tested in six clinical laboratories using three different PCR-based assay platforms. A total of 33 disease alleles was assayed and 25 different alleles were identified. These characterized materials are publicly available from Coriell and may be used for quality control, proficiency testing, test development, and research.
KINETIC CONSEQUENCES OF CONSTRAINING RUNNING BEHAVIOR
Directory of Open Access Journals (Sweden)
John A. Mercer
2005-06-01
Full Text Available It is known that impact forces increase with running velocity as well as when stride length increases. Since stride length naturally changes with changes in submaximal running velocity, it was not clear which factor, running velocity or stride length, played a critical role in determining impact characteristics. The aim of the study was to investigate whether or not stride length influences the relationship between running velocity and impact characteristics. Eight volunteers (mass=72.4 ± 8.9 kg; height = 1.7 ± 0.1 m; age = 25 ± 3.4 years completed two running conditions: preferred stride length (PSL and stride length constrained at 2.5 m (SL2.5. During each condition, participants ran at a variety of speeds with the intent that the range of speeds would be similar between conditions. During PSL, participants were given no instructions regarding stride length. During SL2.5, participants were required to strike targets placed on the floor that resulted in a stride length of 2.5 m. Ground reaction forces were recorded (1080 Hz as well as leg and head accelerations (uni-axial accelerometers. Impact force and impact attenuation (calculated as the ratio of head and leg impact accelerations were recorded for each running trial. Scatter plots were generated plotting each parameter against running velocity. Lines of best fit were calculated with the slopes recorded for analysis. The slopes were compared between conditions using paired t-tests. Data from two subjects were dropped from analysis since the velocity ranges were not similar between conditions resulting in the analysis of six subjects. The slope of impact force vs. velocity relationship was different between conditions (PSL: 0.178 ± 0.16 BW/m·s-1; SL2.5: -0.003 ± 0.14 BW/m·s-1; p < 0.05. The slope of the impact attenuation vs. velocity relationship was different between conditions (PSL: 5.12 ± 2.88 %/m·s-1; SL2.5: 1.39 ± 1.51 %/m·s-1; p < 0.05. Stride length was an important factor
Improved Cuckoo Search (ICS algorthm for constrained optimization problems
Directory of Open Access Journals (Sweden)
Radovan R. Bulatović
Full Text Available Constrained optimization is very important issue in engineering design. The problem of constrained optimization contains the objective function with linear and nonlinear constraint equations. In this paper the Improved Cuckoo Search (ICS algorithm has been applied for solving problems of constrained engineering optimization, which gives better solutions than the standard CS algorithm and the other optimization algorithms used in solving engineering problems from the literature. In the proposed ICS algorithm, dynamic change of parameters of probability and step size is introduced, which are constant in the standard algorithm.
Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation
Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito
2014-02-01
A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.