Random Generation Method Research Articles

МЕТОД ГЕНЕРИРОВАНИЯ ДВУМЕРНОГО БИНАРНОГО СЛУЧАЙНОГО ПРОЦЕССА

The PURPOSE of the study is search for new and modernization of known generation methods of random processes with specified static (probability distribution law) and dynamic (correlation function) probabilistic properties. METHODS. The main research methods used in the study are the probability theory, mathematical statistics and numerical methods. RESULTS. The object of the study is a permutational technology of random process generation with a simultaneously specified probability distribution law and an autocorrelation function. This technology is simple in software implementation, has high response speed and allows to introduce the required probability properties with the accuracy of their reflection, sufficient for engineering applications (e.g. in simulation modeling). The Bernoulli (binary) law is taken as a law of probability distribution of the generated process. The conducted analysis of the probabilistic properties of the behavior of the permutation procedure components has resulted in the identification of new, previously unknown functional capabilities of this method of random process generation. Probabilistic properties (probability distribution laws and autocorrelation functions of the candidate vector components) are systematized depending on a mathematically justified permutation variant. The study is given to two variants of the permutational method that allows to generate a periodically correlated binary process. It is proved that these variants simultaneously provide the possibility to generate a two-dimensional binary random process. CONCLUSION. Conducted theoretical studies allowed to expand the functionalities of the permutational procedure of binary random process generation due to the possibility to generate a two-dimensional random binary process.

Spanning of Meta-Feature Space for Travelling Salesman Problem

In this paper, we consider the problem of creating artificial training set containing instances of a given task with known meta-feature set. We focus on the Traveling salesman problem, however, the approach we present is applicable for any other optimization task. We modify the Smith-Miles approach for spanning of meta-feature space by introducing set diversity function. We use this quality function to reduce instance generation problem to an optimization problem. We can most fully span the whole meta-feature space by maximizing the set diversity quality function. Another method we present to sample an instance set is generating certain instances one by one, making them close to specific meta-feature vectors. In this case, we use Euclidian distance between the given meta-feature vector and obtained instance meta-features as the target function for minimization. We compare these two approaches with the na¨ıve baseline random instance generation method that did not take into account diversity of the obtained instance set. We use genetic algorithm and simulated annealing method as the optimization algorithms used on the meta-level. The value of the set diversity function for the naïve method is equal to 0.123, for the method that directly maximizes diversity by genetic algorithm: 0.468, and for the method that generates single instances by simulated annealing: 0.595.

Using social media and random-generation methods for crowd-sourcing data in nursing research: a pilot project

Using social media and random-generation methods for crowd-sourcing data in nursing research: a pilot project

Using social media and random-generation methods for crowd-sourcing data in rehabilitation research: A pilot project

Using social media and random-generation methods for crowd-sourcing data in rehabilitation research: A pilot project

Large eddy simulation of the neutral atmospheric boundary layer: performance evaluation of three inflow methods for terrains with different roughness

In large eddy simulations (LES) of the atmospheric boundary layer (ABL), the choice of inflow method and the specification of surface roughness are crucial for obtaining accurate results. The consistency between inflow conditions and wall boundary condition has been investigated in depth for the RANS approach, whereas it needs further analysis for LES. This paper investigates the combined effect of inflow method and aerodynamic roughness length for LES of the neutral ABL. Three basic inflow generators in combination with three terrain types are evaluated in terms of streamwise homogeneity of the vertical profiles of mean velocity and turbulence kinetic energy. The results show that the precursor method best preserves the homogeneity of the profiles for all roughness lengths considered, with mean absolute deviations up to 0.7% for mean velocity and 3.5% for turbulence kinetic energy at the outlet of the computational domain. Among the synthetic methods, the Vortex Method performs satisfactorily for mean velocity and, to a lesser extent, turbulence kinetic energy, whereas the random flow generation (RFG) method leads to the largest deviations from the target profiles. Finally, the value of the aerodynamic roughness length is found to only weakly influence the performance of the inflow methods considered.

Random bit generation using coherent state and threshold detectors at 1550 nanometers.

We theoretically propose and experimentally validate a practical random bit generation method based on the detections of a coherent state in the few-photon regime by a gated single-photon threshold detector, operating at the telecom wavelength of 1550 nanometers. By fine tuning the mean number of photons per pulse of a laser beam directed to the single-photon detector, a 50-50 chance of detection or no-detection is reached; under this condition, detections inside the gate window are treated as "1"s, while "0"s are associated with the absence of detections. The same method could also be applied in a free-running single-photon detector for increased throughput by chopping the light signal instead of gating the detector. Both hardware implementations yielded bit strings, which were evaluated by a standard randomness test suite with good confidence. Despite the yet low rates achieved by the proposed method, its hardware compatibility with quantum key distribution setups makes it an interesting candidate for random number generation within the context of practical quantum communications.

Social network information propagation model based on individual behavior

In this paper, we discuss building an information dissemination model based on individual behavior. We analyze the individual behavior related to information dissemination and the factors that affect the sharing behavior of individuals, and we define and quantify these factors. We consider these factors as characteristic attributes and use a Bayesian classifier to classify individuals. Considering the forwarding delay characteristics of information dissemination, we present a random time generation method that simulates the delay of information dissemination. Given time and other constraints, a user might not look at all the information that his/her friends published. Therefore, this paper proposes an algorithm to predict information visibility, i.e., it estimates the probability that an individual will see the information. Based on the classification of individual behavior and combined with our random time generation and information visibility prediction method, we propose an information dissemination model based on individual behavior. The model can be used to predict the scale and speed of information propagation. We use data sets from Sina Weibo to validate and analyze the prediction methods of the individual behavior and information dissemination model based on individual behavior. A previously proposed information dissemination model provides the foundation for a subsequent study on the evolution of the network and social network analysis. Predicting the scale and speed of information dissemination can also be used for public opinion monitoring.

Numerical Study on the Optical and Radiative Properties of the Gradually-varied Volumetric Solar Receiver

Abstract The volumetric solar receiver is one important component of the Concentrated Solar Power (CSP) system. In this paper, a gradually-varied volumetric solar receiver is proposed. Based on a modified random generation method, a 3D model of this type of solar receiver is reconstructed. With the use of Monte Carlo Ray Tracing method (MCRT), the optical and radiative properties of this novel structure are investigated. The result shows that the radiative heat loss could be reduced owing to the lower reflectivity of this novel structure. It also outperforms in the photon absorption compared with the uniform structures that was examined in this paper. Furthermore, a more ideal photon distribution inside the structure is exhibited by the gradually-varied volumetric solar receiver.

167: CRITICALLY APPRAISE OF THE REPORTING QUALITY OF RANDOMIZED CONTROLLED TRIALS ARTICLES IN THE FIELD OF DIABETES IN MEDICAL GUIDELINES IN IRAN

Background and aims:To determine the quality of randomized controlled clinical trial reports in diabetes research in Iran and their presence in domestic and foreign credible guidelines which can imply whether...

МЕТОД ОПРЕДЕЛЕНИЯ ОРИЕНТАЦИИ СОЦИАЛЬНОГО ГРАФА ПО АНАЛИЗУ ВАЛЕНТНОСТИ ВЕРШИН В КОМПОНЕНТЕ СВЯЗНОСТИ

The work is the continuation of the authors’ work on the simulation of the structure of the society by the method of random graphs generation. In their previous works, the authors experimentally proved that the social graph has a strict orientation of the information direction propagation from the shares of the graph with high bonds density to the graph parts having a lower bond density. The authors proposed a method for determining the orientation of the social graph by investigating the ratio of the number of outgoing links to the incoming ones. This method found its application in the analysis of postal mailing, but it turned out to be practically inapplicable in the analysis of social networks, since the counting of incoming and outgoing communications required the compilation of the announced social graphs which was a time-consuming and computational resources task that does not have a solution for polynomial time at present. Since the issue of the social networks analysis is not only of a strictly scientific, but also of a practical interest, the authors developed and tested a technique for determining the orientation of social graphs by the method of analyzing the numerical characteristics of a graph. The new method does not require a detailed analysis of the correspondence of users of social networks, but operates with open user information that is a list of friends (Friend List). The ultimate goal of this work is to develop simple and effective methods for analyzing social networks to identify “opinion leaders”, ways of disseminating information, including propagandizing deviant and dependent forms of behavior, identifying anti-systems and separate closed network communities, and general monitoring of the state of social systems

Analyzing Wireless Indoor Communications by Blockage Models

The performance of wireless cellular networks in indoor scenarios is in large parts characterized by the blockage objects such as walls. These objects can be included in the system model in several ways. We present in this paper different wall generation methods, ranging from approaches from random shape theory (in 1-D and 2-D) to semideterministic and heuristic approaches. To attain comparable results, we ensure that the average wall volume for each method is constant. This results in the same average attenuation for distinct paths, which is shown analytically as well as by simulations. We apply a regular transmitter grid, show the influence of the relative orientation between walls and transmitter–receiver path and also elaborate on the influence of interferers in different tiers around the desired transmitter. Based on the average attenuation, we introduce the necessary approximations to yield tractable expressions for average performance in terms of Signal-to-Interference Ratio (SIR). These approximations are necessary to reflect the fluctuations among the instantaneous SIR values for the individual realizations of the blockage scenario and also due to the spatial correlation of blockages influencing several transmitter-signals simultaneously. Our results show a good accordance among the analytical and simulation results. Furthermore, we find the random wall generation method in two dimensions as the worst case scenario and the regular wall generation method as the best case scenario under the constraint of constant average wall volume.

The quality of surgical versus non-surgical randomized controlled trials.

BackgroundRandomized controlled trials (RCTs) of surgical interventions are often more difficult to conduct, and their quality may lag behind other trials.ObjectivesTo compare quality domains in trials of surgical interventions, to a previously reported control sample of general medical trials from December 2006.Data sourcesMEDLINE, EMBASE and CENTRAL were searched in May 2009.Study eligibilityEnglish language, full text RCTs, performed on humans that compared a surgical intervention to any other intervention.Study appraisal and synthesisRecords were ordered according to their date of publication. The most recently published trials were assessed first, until the required sample of 400 trials was obtained. The search and data collection were piloted by three authors, and was thereafter collected by one author. Data was checked.ResultsAlthough most quality domains were poorly reported, surgical trials compared favourably to general medical trials. Surgical trials were 24% more likely to have an adequate method of random sequence generation, and 71% more likely to have an adequate method of allocation concealment. However, blinding was 40% less likely to be adequate in surgical trials, and sources of funding were 33% less likely to be reported.LimitationsA single author collected most data. Data was checked and this resulted in few changes.ConclusionsReporting of most quality domains in surgical intervention trials was better than general medical trials. Blinding was less likely due to the difficulty in conducting sham surgical trials, and reporting of sources of support should improve with adherence to reporting guidelines.

Assessment of four inflow conditions on large-eddy simulation of a gently curved backward-facing step

ABSTRACTIn this study, we investigated the impact of four different inflow generation methods used in large-eddy simulation on the spatially developing boundary-layer before a recirculation bubble is formed over a gently curved backward-facing step at a Reynolds number 13,700 based on the step height. The configuration under study is very challenging because the separation is caused by a weak adverse pressure gradient, thus making a very sensitive and reliable assessment for evaluating the different inflow conditions used. The first method is a precursor-based simulation in which the velocity data on a certain plane is recorded in a library and then used as the inlet condition for the primary simulation. The second method used is the random noise generation method. The third method is based on generation of turbulent spots which incorporates the distribution of Reynolds stress tensor, and the last one is the so-called rescaling/recycling method proposed by Lund and colleagues. All these methods are compared together in terms of separation and reattachment locations of the recirculation bubble. The flow structures are represented by qualitative criteria, and also streamwise Reynolds stresses and production of turbulent kinetic energy of the flow are assessed and compared together at different stations before and after separation to illuminate how the developing structures within the boundary-layer can affect the locations of separation and reattachment. Distribution of pressure coefficient for different methods showed that there is a relation between production of turbulent kinetic energy and favourable pressure gradient of each method before the separation occurs. Finally, spectra of pressure fluctuation revealed how each inflow condition influences the shedding-instability frequencies.

Elastic percolation of composite structures with regular tessellations of microstructure

Enhancing the mechanical properties of materials by adding inclusions (particles) into microstructure is a favorite research area for material science researchers. In this paper, overall elastic properties of a microstructure are computed taking into account the effects of different geometrical shapes of inclusions. Representative volume elements (RVE) of the material’s microstructures with different tessellations are constructed using a random generation method. The resulting RVEs obtained from the mentioned method were meshed and finite element method (FEM) was used to analyze the deformation of the microstructure including particles under tension and shear loadings. The FE results were then used to compute the stiffness the microstructure. Numerical results are compared with the available theoretical relations. The results show that the dependency of tensile and shearing properties of the microstructure on volume fraction of particles can completely have different trends in some ranges of volume fractions. Also the effects of mechanical percolation on the elastic properties of microstructures were obtained. The presented approach opens a systematic method for investigating the enhanced properties of microstructures with different shapes of tessellations.

Representative volume element for parallel fiber bundles: Model and size convergence

The simulation of textiles often occurs at the meso scale, where the individual tows are treated as a homogeneous continuum. To properly utilize such models, fiber-scale models are required to obtain homogenized tow mechanics and consider fiber-scale mechanisms. The current study demonstrates a representative volume element (RVE) for parallel fiber bundles using the discrete element method (DEM). A method for localization, homogenization, boundary conditions, and random packing generation is presented. An RVE size convergence study was conducted for six different loading cases. An RVE existed for all loading cases, and the smallest RVE which represented a reasonable response contained 162 fibers. Several concerns were highlighted which need to be considered when deciding on an acceptable RVE size for the current model, including loading rate, undulations in the response due to individual fiber slippage, and specimen to specimen variation due to initial fiber positions.

The expected bit complexity of the von Neumann rejection algorithm

In 1952, von Neumann introduced the rejection method for random variate generation. We revisit this algorithm when we have a source of perfect bits at our disposal. In this random bit model, there are universal lower bounds for generating a random variate with a given density to within an accuracy $\epsilon$ derived by Knuth and Yao, and refined by the authors. In general, von Neumann's method fails in this model. We propose a modification that insures proper behavior for all Riemann-integrable densities on compact sets, and show that the expected number of random bits needed behaves optimally with respect to universal lower bounds. In particular, we introduce the notion of an oracle that evaluates the supremum and infimum of a function on any rectangle of $\mathbb{R}^{d}$, and develop a quadtree-style extension of the classical rejection method.

Antibiotics for preventing suppurative complications from undifferentiated acute respiratory infections in children under five years of age.

Undifferentiated acute respiratory infections (ARIs) are a large and heterogeneous group of infections not clearly restricted to one specific part of the upper respiratory tract, which last for up to seven days. They are more common in pre-school children in low-income countries and are responsible for 75% of the total amount of prescribed antibiotics in high-income countries. One possible rationale for prescribing antibiotics is the wish to prevent bacterial complications. To assess the effectiveness and safety of antibiotics in preventing bacterial complications in children aged two months to 59 months with undifferentiated ARIs. We searched the Cochrane Central Register of Controlled Trials (CENTRAL 2015, Issue 7), which contains the Cochrane Acute Respiratory Infections Group's Specialised Register, MEDLINE (1950 to August week 1, 2015) and EMBASE (1974 to August 2015). Randomised controlled trials (RCTs) or quasi-RCTs comparing antibiotic prescriptions with placebo or no treatment in children aged two months to 59 months with an undifferentiated ARI for up to seven days. Two review authors independently assessed trial quality and extracted and analysed data using the standard Cochrane methodological procedures. We identified four trials involving 1314 children. Three trials investigated the use of amoxicillin/clavulanic acid to prevent otitis and one investigated ampicillin to prevent pneumonia.The use of amoxicillin/clavulanic acid compared to placebo to prevent otitis showed a risk ratio (RR) of 0.70 (95% confidence interval (CI) 0.45 to 1.11, three trials, 414 selected children, moderate-quality evidence). Methods of random sequence generation and allocation concealment were not clearly stated in two trials. Performance, detection and reporting bias could not be ruled out in three trials.Ampicillin compared to supportive care (continuation of breastfeeding, clearing of the nose and paracetamol for fever control) to prevent pneumonia showed a RR of 1.05 (95% CI 0.74 to 1.49, one trial, 889 selected children, moderate-quality evidence). The trial was non-blinded. Random sequence generation and allocation concealment methods were not clearly stated, so the possibility of reporting bias could not be ruled out.Harm outcomes could not be analysed as they were expressed only in percentages.We found no studies assessing mastoiditis, quinsy, abscess, meningitis, hospital admission or death. There is insufficient evidence for antibiotic use as a means of reducing the risk of otitis or pneumonia in children up to five years of age with undifferentiated ARIs. Further high-quality research is needed to provide more definitive evidence of the effectiveness of antibiotics in this population.

Study on effective thermal conductivity of silicone/phosphor composite and its size effect by Lattice Boltzmann method

The silicone/phosphor composite is widely used in light emitting diode (LED) packaging. The composite thermal properties, especially the effective thermal conductivity, strongly influence the LED performance. In this paper, a lattice Boltzmann model was presented to predict the silicone/phosphor composite effective thermal conductivity. Based on the present lattice Boltzmann model, a random generation method was established to describe the phosphor particle distribution in composite. Benchmarks were conducted by comparing the simulation results with theoretical solutions for simple cases. Then the model was applied to analyze the effective thermal conductivity of the silicone/phosphor composite and its size effect. The deviations between simulation and experimental results are <7 %, when the phosphor volume fraction varies from 0.038 to 0.45. The simulation results also indicate that effective thermal conductivity of the composite with larger particles is higher than that with small particles at the same volume fraction. While mixing these two sizes of phosphor particles provides an extra enhancement for the effective thermal conductivity.

Transperitoneal versus retroperitoneal approach for elective open abdominal aortic aneurysm repair.

There has been extensive debate in the surgical literature regarding the optimum surgical access approach to the infrarenal abdominal aorta during an operation to repair an abdominal aortic aneurysm. The published trials comparing retroperitoneal (RP) and transperitoneal (TP) aortic surgery show conflicting results. To assess the effectiveness and safety of the transperitoneal versus retroperitoneal approach for elective open abdominal aortic aneurysm repair on mortality, complications, hospital stay and blood loss. The Cochrane Vascular Trials Search Co-ordinator searched the Cochrane Vascular Specialised Register (last searched May 2015) and CENTRAL (2015, Issue 4) and trials databases (May 2015). The review authors searched the Chinese Biomedical Literature Database and other resources including clinical trials registers. We included randomized controlled trials (RCTs) that assessed the TP approach versus the RP approach for elective open abdominal aortic aneurysm (AAA) repair. We evaluated the outcomes of mortality, complications, intensive care unit (ICU) stay, hospital stay, blood loss, aortic cross-clamp time and operating time. Two review authors independently selected RCTs against the inclusion criteria. We resolved any disagreements by discussion with a third review author. Two review authors independently extracted data from the included trials. We resolved any disagreements by discussion with a third review author. Two review authors independently assessed the risk of bias according to a standard quality checklist provided by Cochrane Vascular. We included four RCTs, with a combined total of 129 participants, that assessed the TP approach versus the RP approach for elective open AAA repair. The overall quality of the evidence was low to very low because of the low methodological quality of the included trials (unclear random sequence generation method and allocation concealment, and no blinding of outcome assessors), small sample sizes, small number of events, high heterogeneity and inconsistency between the included trials, no power calculations and relatively short follow-up. There were no differences between the RP approach and the TP approach regarding mortality (odds ratio (OR) 0.32, 95% CI 0.01 to 8.25; 110 participants; four trials; P = 0.49; I² statistic = 0%; very low quality evidence). However, the RP approach may increase complications, such as hematoma (OR 0.90, 95% CI 0.13 to 6.48; 75 participants; two trials; P = 0.92; very low quality evidence), chronic wound pain (OR 2.20, 95% CI 0.36 to 13.34; 48 participants; one trial; P = 0.39; very low quality evidence) and abdominal wall hernia (OR 10.76, 95% CI 0.55 to 211.78; 48 participants; one trial; P = 0.12; very low quality evidence) compared with the TP approach in the patients for elective open AAA repair, but the confidence intervals (CIs) were wide. The RP approach reduced the blood loss (mean difference (MD) -504.87 mL, 95% CI -779.19 to -230.56; 129 participants; four trials; P = 0.003; very low quality evidence), ICU stay (MD -19.00 hours, 95% CI -31.41 to -6.59; 83 participants; two trials; P = 0.003; low quality evidence) and hospital stay (MD -3.14 days, 95% CI -4.82 to -1.45; 129 participants; four trials; P = 0.0003; low quality evidence). There were no differences between the RP approach and the TP approach regarding aortic cross-clamp time (MD 0.69 mins, 95% CI -7.23 to 8.60; 129 participants; four trials; P = 0.86; very low quality evidence) and operating time (MD -15.94 mins, 95% CI -34.76 to 2.88; 129 participants; four trials; P = 0.10; very low quality evidence). Very low quality evidence from four small RCTs indicates that the RP approach did not have advantages over the TP approach for elective open AAA repair in terms of mortality. Moreover, the RP approach may increase the risk of postoperative wound complications although the CIs were wide.Low quality evidence shows that the RP approach could reduce blood loss, hospital stay and ICU stay compared with the TP approach. Very low quality evidence shows no differences between the RP approach and TP approaches in aortic cross-clamp time and operating time.Further large-scale RCTs of the RP approach versus TP approach for elective open AAA repair are required.

Deficiencies of effectiveness of intervention studies in veterinary medicine: a cross-sectional survey of ten leading veterinary and medical journals.

The validity of studies that assess the effectiveness of an intervention (EoI) depends on variables such as the type of study design, the quality of their methodology, and the participants enrolled. Five leading veterinary journals and 5 leading human medical journals were hand-searched for EoI studies for the year 2013. We assessed (1) the prevalence of randomized controlled trials (RCTs) among EoI studies, (2) the type of participants enrolled, and (3) the methodological quality of the selected studies. Of 1707 eligible articles, 590 were EoI articles and 435 RCTs. Random allocation to the intervention was performed in 52% (114/219; 95%CI:45.2–58.8%) of veterinary EoI articles, against 87% (321/371; 82.5–89.7%) of human EoI articles (adjusted OR:9.2; 3.4–24.8). Veterinary RCTs were smaller (median: 26 animals versus 465 humans) and less likely to enroll real patients, compared with human RCTs (OR:331; 45–2441). Only 2% of the veterinary RCTs, versus 77% of the human RCTs, reported power calculations, primary outcomes, random sequence generation, allocation concealment and estimation methods. Currently, internal and external validity of veterinary EoI studies is limited compared to human medical ones. To address these issues, veterinary interventional research needs to improve its methodology, increase the number of published RCTs and enroll real clinical patients.