Constitutive relations for the isotropic deformation of frictionless packings of polydisperse spheres

The isotropic compression of polydisperse packings of frictionless spheres is modeled with the Discrete Element Method (DEM). The evolution of coordination number, fraction of rattlers, isotropic fabric, and pressure (isotropic stress) is reported as function of volume fraction for different system parameters. The power law relationship, with power ≈1/2, between coordination number and volume fraction is confirmed in the jammed state for a broad range of volume fractions and for different (moderate) polydispersities. The polydispersity in the packing causes a shift of the critical volume fraction, i.e., more heterogeneous packings jam at higher volume fractions. Close to jamming, the coordination number and the jamming volume fraction itself depend on both history and rate. At larger densities, neither the deformation history nor the loading rate have a significant effect on the evolution of the coordination number.\ud \ud Concerning the fabric tensor, comparing our DEM results to theoretical predictions, good agreement for different polydispersities is observed. An analytical expression for the pressure as function of isotropic (volumetric) strain is proposed for polydisperse packings, based on the assumption of uniform deformation. We note that, besides the implicit proportionality to contact number density (or fabric), no single power-law is evidenced in the relation between pressure and isotropic strain. However, starting from zero pressure at the jamming point, a linear term with a quadratic correction describes the stress evolution rather well for a broad range of densities and for various polydispersities. Finally, an incremental evolution equation is proposed for both fabric and stress, as function of isotropic strain, and involving the coordination number and the fraction of rattlers, as starting point for further studies involving anisotropic deformations

Jamming in frictionless packings of spheres: determination of the critical volume fraction

The jamming transition in granular packings is characterized by a sudden change in the coordination number. In this work we investigate the evolution of coordination number as function of volume fraction for frictionless packings of spheres undergoing isotropic deformation. Using the results obtained from Discrete Element Method simulations, we confirm that the coordination number depends on volume fraction by a power law with exponent α≈0.5 above the critical volume fraction and up to rather high densities. We find that the system size and loading rate do not have an important effect on the evolution of the coordination number. Polydispersity of the packing seems to cause a shift in the critical volume fraction, i.e., more heterogeneous packings jam at higher volume fractions. Finally, we propose and evaluate alternative methods to determine the critical volume fraction based on the number of rattlers, the pressure and the ratio of kinetic and potential energies. The results are all consistent with the critical volume fractions obtained from the fits of the power law to the simulation data

Influence of different CO2 levels on the growth, competition and herbicide sensitivity of some important weeds in maize (Zea mays L.)

Bu çalışmada farklı CO2 oranlarının mısır (Zea mays L.)’da sorun oluşturan Sorghum halepense, Echinochloa cruss-galli, Amaranthus blitoides ve Solanum nigrum ‘un gelişimi, rekabeti ve herbisit duyarlılığının belirlenmesi amaçlanmıştır. Çalışmada, karbondioksitin yabancı otların çıkışına olan etkisi iki farklı ortamdaki çıkış oranının birbiriyle karşılaştırılması suretiyle bulunmuştur. CO2 'nin rekabetli (mısır + yabancı ot) ve rekabetsiz ortamda yetişen bitkilerin gelişimine olan etkileri de yapılan çalışmalarla belirlenmiştir. Yabancı otların farklı CO2 koşullarında herbisite duyarlılıklarının belirlenebilmesi amacıyla da denemeler kurulmuştur. Araştırmalar sonucunda yüksek CO2 oranı, bazı yabancı otların çıkışını olumlu yönde etkilemiştir. Rekabet koşulları değerlendirildiğinde ise; rekabetsiz ortamda yetişen mısır bitkilerinin normal CO2 koşullarında, rekabet durumunda ise yüksek CO2 koşullarında biyomasının normale oranla daha yüksek olduğu görülmüştür. Böylece normal CO2 koşullarında çoğu durumda yabancı otlar mısır gelişimini azaltırken, yüksek CO2 koşullarında ise mısır gelişiminde yabancı ot rekabetinden kaynaklanan bir azalma görülmemiştir. Yabancı otların da gelişim parametrelerinin yüksek CO2 ve rekabet koşullarında daha yüksek değerlere ulaştığı tespit edilmiştir. Genellikle yüksek CO2 koşullarının herbisit etkinliğinde azalmaya neden olabileceği de belirlenmiştir. Elde edilen bu bulgular gelecekte söz konusu olan atmosferik CO2 oranındaki artışların mısır ile yabancı otlar arasındaki rekabeti ve mısırda yabancı ot mücadelesini önemli oranda etkileyeceğini göstermiştir.The aim of this study was to investigate the effect of different CO2 levels on the growth, competition and herbicide sensitivities of Sorghum halepense, Echinochloa cruss-galli, Amaranthus blitoides and Solanum nigrum in maize (Zea mays L.). The effect of two different CO2 level on the emergence of weed was investigated as the first step of the studies. This step was followed by studies concerning the growth of weeds and maize under ambient and elevated CO2 conditions each with and without concurrence with maize/weeds. The last step of the study was to compare the herbicide sensitivities of the weeds under tested CO2 conditions. Results showed that elevated CO2 resulted with higher emergence rates in the case of some weeds. Maize growth was influenced by CO2 levels depending on the competitive conditions, so that under elevated CO2 conditions maize plants produced less biomass without competition while the biomass of maize was higher in the case of competition with weeds. Weed competition reduced in some experiments weed biomass significantly under ambient CO2 conditions, while no biomass reduction occurred under elevated CO2 conditions in most cases. Also weed response to elevated CO2 was variable depending on competitive conditions. Weed growth was generally improved by high CO2 under competitive conditions with weeds. Results of herbicide sensitivity experiments showed that elevated CO2 caused in general lower herbicide effects. The results of these studies showed that the increase in the future atmospheric CO2 level would influence the competition between maize and weeds, as well as the success of weed control measurements

Employees’ relative deprivation for females and supervisory commitment: The mediating roles of interpersonal justice, informational justice, and perceived empathy

The present study aims to test a model derived from a conceptual framework that attempted to explain negative interactions among supervisor-employee dyads from a Relative Deprivation Theory (RDT) and justice-related perspective. Employees’ perceptions of fraternal (group) deprivation on part of females compared to males in their organizations were suggested to be related to their interpersonal and informational justice perceptions as well as their perceptions of supervisors’ empathy. Employees’ perceptions of justice and empathy, in turn, were suggested to be positively associated with overall supervisory commitment. Moreover, the moderating effects of employee gender on the proposed relationships were investigated. The data was collected from 114 employees who were enrolled in undergraduate classes in a Southwestern university in USA. The proposed model as well as the alternative models were tested by Structural Equation Modeling (SEM) technique using AMOS 6.0 software. The findings revealed that proposed mediated model was supported by the data for the independent variable of employee perceptions of “affective” relative deprivation for females in the organization and for the dependent variables of “affective supervisory commitment” and “continuance supervisory commitment”. However, employees’ gender did not have a moderating effect on the relationships in the mediated model that was supported by the data. The results are discussed in terms of their theoretical and practical implications as well as the suggestions for future research

Long-term outcomes of omniflow II biosynthetic vascular graft in lower extremity arterial revascularization

Background: This study aims to evaluate the patency rates and long-term outcomes of femoro-popliteal bypass procedures with Omniflow II biosynthetic vascular grafts in patients with occlusive vascular disease. Methods: This retrospective, observational, clinical study included a total of 93 patients (61 males, 32 females; mean age 56.9±7.4 years; range, 43 to 83 years) who underwent femoro-popliteal bypass in which Omniflow II biosynthetic vascular grafts were used due to peripheral arterial disease. The patients were divided into two groups: 62 patients undergoing femoro-popliteal above-knee bypass and 31 patients undergoing the femoro-popliteal belowknee bypass. We evaluated preoperative clinical characteristics, postoperative graft patency rates, and other clinical results. Results: The mean follow-up was 44.9±18.8 months in the femoropopliteal above-knee bypass group and 47.3±22.3 months in the femoro-popliteal below-knee bypass group (p=0.302). The cumulative primary graft patency rates of the femoro-popliteal above-knee bypass and femoro-popliteal below-knee bypass groups at three, four, and five years were 98%, 95% and 78% and 86%, 75% and 45%, respectively (log-rank; p=0.312). The cumulative assisted graft patency rates of the femoro-popliteal above-knee bypass and femoro-popliteal below-knee bypass groups at five years were 87.9% and 65.3%, respectively (log-rank; p=0.530). Conclusion: The Omniflow II biosynthetic vascular graft is suitable for above-and below-knee femoro-popliteal bypass procedures. These grafts may be prefered due to high patency rates, low incidence of aneursym formations, and infections. ©2018 All right reserved by the Turkish Society of Cardiovascular Surgery

From particle simulations to macroscopic constitutive relations

The goal is to determine the constitutive behavior of granular packings under various deformations (isotropic and anisotropic) from particle simulations. For this we consider deformations, stress, structure and the contact forces as the basis. In a previous study [6,7] we investigated using DEM, the evolution of the coordination number (and the packing structure) and pressure as functions of the volume fraction for a polydisperse granular packing of spheres under isotropic compression. Here we focus on anisotropic deformation by implementing the triaxial test setup in a similar way. We study the effect of polydispersity changing the width of the particle size distribution. We find that an increase in polydispersity leads to a decrease in pressure at constant volume fraction whereas the macroscopic friction angle seems to increase with polydispersity. Furthermore, we performed triaxial test simulations with soft friction which is characterized by a small tangential contact stiffness. Our main observation is that using the same initial packing configuration with different friction coefficients does not lead to an obvious trend in simulation results

The Innovative Techniques in Animal Husbandry

Technology is developing rapidly. In this development, the transfer of computer systems and software to the application has made an important contribution. Technologic instruments made farmers can work more comfortable and increased animal production efficiency and profitability. Therefore, technologic developments are the main research area for animal productivity and sustainability. Many technologic equipment and tools made animal husbandry easier and comfortable. Especially management decisions and applications are effected highly ratio with this rapid development. In animal husbandry management decisions that need to be done daily are configured according to the correctness of the decisions to be made. At this point, smart systems give many opportunities to farmers. Milking, feeding, environmental control, reproductive performance constitute everyday jobs most affected by correct management decisions. Human errors in this works and decisions made big effect on last product quality and profitability are not able to be risked. This chapter deal with valuable information on the latest challenges and key innovations affecting the animal husbandry. Also, innovative approaches and applications for animal husbandry are tried to be summarized with detail latest research results

Exploiting pattern transformation to tune phononic band gaps in a two-dimensional granular crystal

The band structure of a two-dimensional granular crystal composed of silicone rubber and polytetrafluoroethylene (PTFE) cylinders is investigated numerically. This system was previously shown to undergo a pattern transformation with uniaxial compression by Göncü et al. [Soft Matter 7, 2321 (2011)]. The dispersion relations of the crystal are computed at different levels of deformation to demonstrate the tunability of the band structure, which is strongly affected by the pattern transformation that induces new band gaps. Replacement of PTFE particles with rubber ones reveals that the change of the band structure is essentially governed by pattern transformation rather than particles¿ mechanical properties

EVALUATION OF LOCATION SELECTION CRITERIA FOR COORDINATION MANAGEMENT CENTERS AND LOGISTIC SUPPORT UNITS IN DISASTER AREAS WITH AHP METHOD

In recent years, human beings and our planet have suffered great losses in the frequent disasters. Effective and timely intervention is of utmost importance in all large-scale disasters, whether natural or man-made. In this article, a study has been conducted on a model in which the location selection criteria of the management and support centers, where the coordination works as well as the management and administration are carried out in disaster areas, are evaluated by the Multi-Criteria Decision Making (MCDM) method. For this, an in-depth literature analysis was carried out at the first stage, and then all the findings obtained as a result of the literature research were presented to the professionals related to the subject, and expert opinion was sought. In the light of expert opinion, the location selection criteria for the coordination management center and logistic support units in disaster areas were determined, and a model proposal was made, in which the importance values ​​were weighted by using one of the MCDM methods, The Analytic Hierarchy Process (AHP), which is widely used

Multi-objective Optimization Framework for Trade-Off Among Pedestrian Delays and Vehicular Emissions at Signal-Controlled Intersections

Traffic congestion has several adverse effects on urban traffic networks. Increased travel times of vehicles, with the addition of excessive greenhouse emissions, can be listed as harmful effects. To address these issues, transportation engineers aim to reduce private car usage, reduce travel times through different control strategies, and mitigate harmful effects on urban networks. In this study, we introduce an innovative approach to optimizing traffic signal control settings. This methodology takes into account both pedestrian delays and vehicular emissions. Non-dominated sorting genetic algorithm-II and Multiobjective Artificial Bee Colony algorithms are adopted to solve the multi-objective optimization problem. The vehicular emissions are modeled through the MOVES3 emission model and integrated into the utilized microsimulation environment. Initially, the proposed framework is tested on a hypothetical test network, followed by a real-world case study. Results indicate a significant improvement in pedestrian delays and lower emissions