Search results for: turbulence transition

Authors: Ryota Kuzuki, Mitsuhiro Kohara, Noboru Kizuki, Satoshi Yoshida, Hidetaka Hirai, Yuta Nezasa

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About fifty years have passed since Japan's gas supply industry became the first in the world to switch from coal and oil to LNG as a city gas feedstock. Since the Japanese government target of net-zero carbon emission in 2050 was announced in October 2020, it has now entered a new era of challenges to commit to the requirement for decarbonization. This paper describes the situation that synthetic methane, produced from renewable energy-derived hydrogen and recycled carbon, is a promising national policy of transition toward net-zero society. In November 2020, the Japan Gas Association announced the 'Carbon Neutral Challenge 2050' as a vision to contribute to the decarbonization of society by converting the city gas supply to carbon neutral. The key technologies is methanation. This paper shows that methanation is a realistic solution to contribute to the decarbonization of the whole country at a lower social cost, utilizing the supply chain that already exists, from LNG plants to burner chips. The challenges during the transition period (2030-2050), as CO2 captured from exhaust of thermal power plants and industrial factories are expected to be used, it is proposed that a system of guarantee of origin (GO) for H2 and CO2 should be established and harmonize international rules for calculating and allocating greenhouse gas emissions in the supply chain, a platform is also needed to manage tracking information on certified environmental values.

Keywords: synthetic methane, recycled carbon fuels, methanation, transition period, environmental value transfer platform

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Authors: Sabrina Nouri, Abderahmane Ghezal, Said Abboudi, Pierre Spiteri

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This paper deals with the numerical study of heat and mass transfer of laminar flow transition at low Prandtl numbers. The model includes the two-directional momentum, the energy and mass transfer equations. These equations are discretized by the finite volume method and solved by a self-made simpler like Fortran code. The effect of governing parameters, namely the Lewis and Prandtl numbers, on the transition of the flow and solute distribution is studied for positive and negative thermal and solutal buoyancy forces ratio. Nusselt and Sherwood numbers are derived for of Prandtl [10⁻²-10¹] and Lewis numbers [1-10⁴]. The results show unicell and multi-cell flow. Solute and flow boundary layers appear for low Prandtl number.

Keywords: natural convection, low Prandtl number, heat and mass transfer, finite volume method

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Authors: Ying-Chang Yu, Yuan-Lung Lo

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Building envelope design is one of the most popular design fields of architectural profession in nowadays. The main design trend of such system is to highlight the designer's aesthetic intention from the outlook of building project. Due to the trend of current façade design, the building envelope contains more and more layers of components, such as double skin façade, photovoltaic panels, solar control system, or even ornamental components. These exterior components are designed for various functional purposes. Most researchers focus on how these exterior elements should be structurally sound secured. However, not many researchers consider these elements would help to improve the performance of façade system. When the exterior elements are deployed in large scale, it creates an additional layer outside of original façade system and acts like a porous interface which would interfere with the aerodynamic of façade surface in micro-scale. A standard façade performance consists with 'water penetration, air infiltration rate, operation force, and component deflection ratio', and these key performances are majorly driven by the 'Design Wind Load' coded in local regulation. A design wind load is usually determined by the maximum wind pressure which occurs on the surface due to the geometry or location of building in extreme conditions. This research was designed to identify the air damping phenomenon of micro turbulence caused by porous exterior layer leading to surface wind load reduction for improvement of façade system performance. A series of wind tunnel test on dynamic pressure sensor array covered by various scale of porous exterior skin was conducted to verify the effect of wind pressure reduction. The testing specimens were designed to simulate the typical building with two-meter extension offsetting from building surface. Multiple porous exterior skins were prepared to replicate various opening ratio of surface which may cause different level of damping effect. This research adopted 'Pitot static tube', 'Thermal anemometers', and 'Hot film probe' to collect the data of surface dynamic pressure behind porous skin. Turbulence and distributed resistance are the two main factors of aerodynamic which would reduce the actual wind pressure. From initiative observation, the reading of surface wind pressure was effectively reduced behind porous media. In such case, an actual building envelope system may be benefited by porous skin from the reduction of surface wind pressure, which may improve the performance of envelope system consequently.

Keywords: multi-layer facade, porous media, facade performance, turbulence and distributed resistance, wind tunnel test

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Authors: Bo Zhang, Ellen S. Wilschut, Dehlia M. C. Willemsen, Marieke H. Martens

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With the rapid development of intelligent transportation systems, automated platooning of trucks is drawing increasing interest for its beneficial effects on safety, energy consumption and traffic flow efficiency. Nevertheless, one major challenge lies in the safe transition of control from the automated system back to the human drivers, especially when they have been inattentive after a long period of highly automated driving. In this study, we investigated driver take-over time after a system initiated request to leave the platooning system Virtual Tow Bar in a non-critical scenario. 22 professional truck drivers participated in the truck driving simulator experiment, and each was instructed to drive under three experimental conditions before the presentation of the take-over request (TOR): driver ready (drivers were instructed to monitor the road constantly), driver not-ready (drivers were provided with a tablet) and eye-shut. The results showed significantly longer take-over time in both driver not-ready and eye-shut conditions compared with the driver ready condition. Further analysis revealed hand movement time as the main factor causing long response time in the driver not-ready condition, while in the eye-shut condition, gaze reaction time also influenced the total take-over time largely. In addition to comparing the means, large individual differences can be found especially in two driver, not attentive conditions. The importance of a personalized driver readiness predictor for a safe transition is concluded.

Keywords: driving simulation, highly automated driving, take-over time, transition of control, truck platooning

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Authors: Jae-Yeong Choi, Gyu-Mok Jeon, Jong-Chun Park, Yong-Jin Cho, Seok-Tae Yoon

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When air flow is injected into water, bubbles are formed in various types inside the water pool along with the air flow rate. The bubbles are floated in equilibrium with forces such as buoyancy, surface tension and shear force. Single bubble generated at low flow rate maintains shape, but bubbles with high flow rate break up to make mixing and turbulence. In addition to this phenomenon, as the hot air bubbles are injected into the water, heat affects the interface of phases. Therefore, the main scope of the present work reveals how to proceed heat transfer between water and hot air bubbles injected into water. In the present study, a series of CFD simulation for the heat transfer of hot bubbles injected through a nozzle near the bottom in a cylindrical water column are performed using a commercial CFD software, STAR-CCM+. The governing equations for incompressible and viscous flow are the continuous and the RaNS (Reynolds- averaged Navier-Stokes) equations and discretized by the FVM (Finite Volume Method) manner. For solving multi-phase flow, the Eulerian multiphase model is employed and the interface is defined by VOF (Volume-of-Fluid) technique. As a turbulence model, the SST k-w model considering the buoyancy effects is introduced. For spatial differencing the 3th-order MUSCL scheme is adopted and the 2nd-order implicit scheme for time integration. As the results, the dynamic behavior of the rising hot bubbles with the flow rate injected and regarding heat transfer mechanism are discussed based on the simulation results.

Keywords: heat transfer, hot bubble injection, eulerian multiphase model, flow rate, CFD (Computational Fluid Dynamics)

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Authors: Sagar Saroha, Sawan S. Sinha, Sunil Lakshmipathy

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Reynolds averaged Navier-Stokes (RANS) model is the popular computational tool for prediction of turbulent flows. Being computationally less expensive as compared to direct numerical simulation (DNS), RANS has received wide acceptance in industry and research community as well. However, for high Reynolds number flows, the traditional RANS approach based on the Boussinesq hypothesis is incapacitated to capture all the essential flow characteristics, and thus, its performance is restricted in high Reynolds number flows of practical interest. RANS performance turns out to be inadequate in regimes like flow over curved surfaces, flows with rapid changes in the mean strain rate, duct flows involving secondary streamlines and three-dimensional separated flows. In the recent decade, partially averaged Navier-Stokes (PANS) methodology has gained acceptability among seamless bridging methods of turbulence- placed between DNS and RANS. PANS methodology, being a scale resolving bridging method, is inherently more suitable than RANS for simulating turbulent flows. The superior ability of PANS method has been demonstrated for some cases like swirling flows, high-speed mixing environment, and high Reynolds number turbulent flows. In our work, we intend to evaluate PANS in case of separated turbulent flows past bluff bodies -which is of broad aerodynamic research and industrial application. PANS equations, being derived from base RANS, continue to inherit the inadequacies from the parent RANS model based on linear eddy-viscosity model (LEVM) closure. To enhance PANS’ capabilities for simulating separated flows, the shortcomings of the LEVM closure need to be addressed. Inabilities of the LEVMs have inspired the development of non-linear eddy viscosity models (NLEVM). To explore the potential improvement in PANS performance, in our study we evaluate the PANS behavior in conjugation with NLEVM. Our work can be categorized into three significant steps: (i) Extraction of PANS version of NLEVM from RANS model, (ii) testing the model in the homogeneous turbulence environment and (iii) application and evaluation of the model in the canonical case of separated non-homogeneous flow field (flow past prismatic bodies and bodies of revolution at high Reynolds number). PANS version of NLEVM shall be derived and implemented in OpenFOAM -an open source solver. Homogeneous flows evaluation will comprise the study of the influence of the PANS’ filter-width control parameter on the turbulent stresses; the homogeneous analysis performed over typical velocity fields and asymptotic analysis of Reynolds stress tensor. Non-homogeneous flow case will include the study of mean integrated quantities and various instantaneous flow field features including wake structures. Performance of PANS + NLEVM shall be compared against the LEVM based PANS and LEVM based RANS. This assessment will contribute to significant improvement of the predictive ability of the computational fluid dynamics (CFD) tools in massively separated turbulent flows past bluff bodies.

Keywords: bridging methods of turbulence, high Re-CFD, non-linear PANS, separated turbulent flows

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Authors: Md. Jahoor Alam

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Recent studies suggest that Glucose controls several lifesaving pathways. Glucose molecule is reported to be responsible for the production of ROS (reactive oxygen species). In the present work, a p53-MDM2-Glucose model is developed in order to study spatiotemporal properties of the p53 pathway. The systematic model is mathematically described. The model is numerically simulated using high computational facility. It is observed that the variation in glucose concentration level triggers the system at different states, namely, oscillation death (stabilized), sustain and damped oscillations which correspond to various cellular states. The transition of these states induced by glucose is phase transition-like behaviour. Further, the amplitude of p53 dynamics with the variation of glucose concentration level follows power law behaviour, As(k) ~ kϒ, where, ϒ is a constant. Further Stochastic approach is needed for understanding of realistic behaviour of the model. The present model predicts the variation of p53 states under the influence of glucose molecule which is also supported by experimental facts reported by various research articles.

Keywords: oscillation, temporal behavior, p53, glucose

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Authors: Nisha Deopa, A. S. Rao

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Lithium Lead Alumino Borate (LiPbAlB) glasses doped with different Dy3+ ions concentration were synthesized to investigate their viability in solid state lighting (SSL) technology by melt quenching techniques. From the absorption spectra, bonding parameters (ð) were investigated to study the nature of bonding between Dy3+ ions and its surrounding ligands. Judd-Ofelt (J-O) intensity parameters (Ω = 2, 4, 6), estimated from the experimental oscillator strengths (fex) of the absorption spectral features were used to evaluate the radiative parameters of different transition levels. From the decay curves, experimental lifetime (τex) were measured and coupled with the radiative lifetime to evaluate the quantum efficiency of the as-prepared glasses. As Dy3+ ions concentration increases, decay profile changes from exponential to non-exponential through energy transfer mechanism (ETM) in turn decreasing experimental lifetime. In order to investigate the nature of ETM, non-exponential decay curves were fitted to Inkuti–Hirayama (I-H) model which further confirms dipole-dipole interaction. Among all the emission transition, 4F9/2  6H15/2 transition (483 nm) is best suitable for lasing potentialities. By exciting titled glasses in n-UV to blue regions, CIE chromaticity coordinates and Correlated Color Temperature (CCT) were calculated to understand their capability in cool white light generation. From the evaluated radiative parameters, CIE co-ordinates, quantum efficiency and confocal images it was observed that glass B (0.5 mol%) is a potential candidate for developing w-LEDs and lasers.

Keywords: energy transfer, glasses, J-O parameters, photoluminescence

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Authors: Abas Mohsenzadeh, Mina Arya, Kim Bolton

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Catalytic combustion of hydrocarbons is an important technology developed to produce energy with minimum pollutant formation. The catalyst plays a key role in this process which operates at lower temperatures compared to conventional flame combustion. The energetics of the direct combustion of hydrocarbons (CH → C + H) on a series of metal surfaces including Ag, Au, Al, Cu, Rh, Pt, Pd, Ni, Fe and Co were investigated using density functional theory (DFT). Brønsted-Evans-Polanyi (BEP) and transition state scaling (TSS) correlations were proposed based on DFT calculations on the Ag, Au, Al, Cu, Rh, Pt and Pd surfaces. These correlations were then used to estimate the energetics on Fe, Ni and Co surfaces. Results showed that the estimated reaction and activation energies by BEP and TSS correlations on Fe, Ni and Co surfaces are in an excellent agreement with those obtained by DFT calculations. Therefore these correlations can be efficiently used to predict energetics of similar reactions on these surfaces without doing computationally costly transition state calculations. It was found that the activation barrier for CH dissociation follows the order Ag ˃ Au ˃ Al ˃ Cu ˃ Pt ˃ Pd ˃ Ni > Co > Rh > Fe. Also, BEP (with R2 value of 0.96) and TSS correlations (with R2 value of 0.99) support the results.

Keywords: BEP, DFT, hydrocarbon combustion, metal surfaces, TSS

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Authors: Domagoj Hruska, Drazen Milkovic, Maja Darabos

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This paper empirically investigates the performance of Croatian initial public offerings (IPOs) throughout 20 years period, from 1996 until 2016. By proving the comprehensive evaluation of reasons and consequences of IPO initiatives in Croatia we give analytic evidence on the influence of this corporate action on the development of corporate governance. Furthermore, the paper discusses the relationship between internal and external corporate governance mechanisms in companies that initialize entering the financial markets. The paper will provide a synthesis of evidence of IPO-s in Croatia based on in-depth case studies of 13 cases of IPO-s. The major findings of the paper include identification of reasons for conducting IPO-s and calculation of underpricing effect and change of market capitalization. To the best of the author's knowledge, the results of the paper provide the analytical framework for understanding the impact of IPOs on the corporate governance system in transition countries.

Keywords: corporate governance, Croatia, initial public offering, transition economy

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Authors: Budiman Ibnu

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This study investigates about enabling conditions to facilitate social innovation in the energy sector. This is important to support the energy transition in Indonesia. This research provides appropriate project direction, including research (and action) gaps for the energy actors in Indonesia. The actors are allowed to work further with the result of this study to stimulate the energy transition in Indonesia. This report uses systemic change framework which recognizes four drivers of systemic change in a region: 1. transforming political ecologies; 2. configuring green economies; 3. building of adaptive communities; 4. social innovation. These drivers are interconnected, and this report particularly focuses on how social innovation can be supported by other drivers. This study used methods of interview and literature review as the main sources for data collection in this report. There were interviews with eight experts in the related topic which come from different countries which have experienced social innovation in the energy sector. Afterwards, this research reviewed related journal papers from last five years, to check the latest development within the topic, to support the interview result. The result found that the enabling condition can focus on one of the drivers of systemic change, which is building communities by increasing their participation, through several integrated actions. This can be implemented in two types of citizen energy initiatives which are energy cooperatives and sustainable consumption initiatives. This implementation requires study about its related policy and governance support, in order to create complete enabling conditions to facilitate social innovation in the energy transition.

Keywords: enabling condition, social innovation, citizen initiatives, community participation

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Authors: Young Sik Kim, Tae Kwon Ha

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High strength Fe-36Ni-base Invar alloys containing Al contents up to 0.3 weight per cent were cast into ingots and thermodynamic equilibrium during solidification has been investigated in this study. From the thermodynamic simulation using Thermo-Calc®, it has been revealed that equilibrium phases which can be formed are two kinds of MC-type precipitates, MoC, and M2C carbides. The mu phase was also expected to form by addition of aluminum. Microstructure observation revealed the coarse precipitates in the as-cast ingots, which was non-equilibrium phase and could be resolved by the successive heat treatment. With increasing Al contents up to 0.3 wt.%, tensile strength of Invar alloy increased as 1400MPa after cold rolling and thermal expansion coefficient increased significantly. Cold rolling appeared to dramatically decrease thermal expansion coefficient.

Keywords: Invar alloy, transition metals, phase equilibrium, aging behavior, microstructure, hardness

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Authors: Shusmita Khan, Shams El Arifeen, Kanta Jamil

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Background: Nutrition transition in Bangladesh has progressed across various relevant socio-demographic contextual issues. For a developing country like Bangladesh, its is believed that, overnutrition is less prevalent than undernutrition. However, recent evidence suggests that a rapid shift is taking place where overweight is subduing underweight. With this rapid increase, for Bangladesh, it will be challenging to achieve the global agenda on halting overweight and obesity. Methods: A secondary analysis was performed from six successive national demographic and health surveys to get the trend on undernutrition and overnutrition for women from reproductive age. In addition, national relevant policy papers were reviewed to determine the countries readiness for whole of the systems approach to tackle this epidemic. Results: Over the last decade, the proportion of women with low body mass index (BMI<18.5), an indicator of undernutrition, has decreased markedly from 34% to 19%. However, the proportion of overweight women (BMI ≥25) increased alarmingly from 9% to 24% over the same period. If the WHO cutoff for public health action (BMI ≥23) is used, the proportion of overweight women has increased from 17% in 2004 to 39% in 2014. The increasing rate of obesity among women is a major challenge to obstetric practice for both women and fetuses. In the long term, overweight women are also at risk of future obesity, diabetes, hyperlipidemia, hypertension, and heart disease. These diseases have serious impact on health care systems. Costs associated with overweight and obesity involves direct and indirect costs. Direct costs include preventive, diagnostic, and treatment services related to obesity. Indirect costs relate to morbidity and mortality costs including productivity. Looking at the Bangladesh Health Facility Survey, it is found that the country is bot prepared for providing nutrition-related health services, regarding prevention, screening, management and treatment. Therefore, if this nutrition transition is not addressed properly, Bangladesh will not be able to achieve the target of the NCD global monitoring framework of the WHO. Conclusion: Addressing this nutrition transition requires contending ‘malnutrition in all its forms’ and addressing it with integrated approaches. Whole of the systems action is required at all levels—starting from improving multi-sectoral coordination to scaling up nutrition-specific and nutrition-sensitive mainstreamed interventions keeping health system in mind.

Keywords: nutrition transition, Bangladesh, health system, undernutrition, overnutrition, obesity

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Authors: Jinge Liu, Shuyuan Min, Bingchuan Liu, Bangzhao Yin, Bo Peng, Peng Wen, Yun Tian

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WE43 magnesium alloy can be additively manufactured via laser powder bed fusion (LPBF) for biodegradable applications, but the as-built WE43 exhibits an excessively rapid corrosion rate. High-temperature oxidation (HTO) was performed on the as-built WE43 to improve its biodegradation behavior. A sandwich structure including an oxide layer at the surface, a transition layer in the middle, and the matrix was generated influenced by the oxidation reaction and diffusion of RE atoms when heated at 525 ℃for 8 hours. The oxide layer consisted of Y₂O₃ and Nd₂O₃ oxides with a thickness of 2-3 μm. The transition layer is composed of α-Mg and Y₂O₃ with a thickness of 60-70 μm, while Mg24RE5 could be observed except α-Mg and Y₂O₃. The oxide layer and transition layer appeared to have an effective passivation effect. The as-built WE43 lost 40% weight after the in vitro immersion test for three days and finally broke into debris after seven days of immersion. The high-temperature oxidation samples kept the structural integrity and lost only 6.88 % weight after 28-day immersion. The corrosion rate of HTO samples was significantly controlled, which improved the biocompatibility of the as-built WE43 at the same time. The samples after HTO had better osteogenic capability according to ALP activity. Moreover, as built WE43 performed unqualified in cell adhesion and hemolytic test due to its excessively rapid corrosion rate. While as for HTO samples, cells adhered well, and the hemolysis ratio was only 1.59%.

Keywords: laser powder bed fusion, biodegradable metal, high temperature oxidation, biodegradation behavior, WE43

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Authors: Raheel Asif, Michael Frommel

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This paper focuses on analyzing the exchange rate exposure of exporting & domestic firms in (the so far rarely addressed) largest Eastern European transition economies, i.e., Russia and the three EU accession countries, Poland, Hungary, and Czech Republic (CEEC-3). It also controls for possible effects of different exchange rate regimes, Great Financial crisis (2007-08), Russian Financial crisis (2014-15), the formation of EU & turn of year effect. Substantially improving the results from the existing literature on these transition economies, we find for more than 51% of our sample firms in CEEC-3 countries and 29% in Russia shows a significant exchange rate exposure. However, the magnitude and direction of firms’ exposure depends on the particular bilateral exchange rate and differs between CEEC-3 and Russia. We find that share price increases with an appreciation of the domestic currency against the EURO and US Dollar (USD) in CEEC-3; however, the effect is more pronounced for EURO as expected. Whereas, for Russian firms share price increases with a depreciation of the domestic currency against the USD only. Those differences may result from a differing dominance of exposure channels in the respective economies, such as the country-specific export structure, competitiveness channels, and dependence on foreign debt. Finally, the switch from a pegged to a flexible exchange rate regime appears to have a less pronounced effect for the exchange rate exposure of firms in all countries except for USD in Poland and Russia.

Keywords: exchange rate exposure, transition economies, central and eastern Europe, international finance

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Authors: S. M. Rifat, André L. Marchildon, Mark F. Tachie

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Experiments were performed to investigate the effects of roughness on the reattachment and redevelopment regions over a 12 mm forward facing step (FFS) in an open channel flow. The experiments were performed over an upstream smooth wall and a smooth FFS, an upstream wall coated with sandpaper 36 grit and a smooth FFS and an upstream rough wall produced from sandpaper 36 grit and a FFS coated with sandpaper 36 grit. To investigate only the wall roughness effects, Reynolds number, Froude number, aspect ratio and blockage ratio were kept constant. Upstream profiles showed reduced streamwise mean velocities close to the rough wall compared to the smooth wall, but the turbulence level was increased by upstream wall roughness. The reattachment length for the smooth-smooth wall experiment was 1.78h; however, when it is replaced with rough-smooth wall the reattachment length decreased to 1.53h. It was observed that the upstream roughness increased the physical size of contours of maximum turbulence level; however, the downstream roughness decreased both the size and magnitude of contours in the vicinity of the leading edge of the step. Quadrant analysis was performed to investigate the dominant Reynolds shear stress contribution in the recirculation region. The Reynolds shear stress and turbulent kinetic energy profiles after the reattachment showed slower recovery compared to the streamwise mean velocity, however all the profiles fairly collapse on their corresponding upstream profiles at x/h = 60. It was concluded that to obtain a complete collapse several more streamwise distances would be required.

Keywords: forward facing step, open channel, separated and reattached turbulent flows, wall roughness

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Authors: Raina J. Olsen, Andrew K. Gillespie, John W. Taylor, Cristian I. Contescu, Peter Pfeifer, James R. Morris

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While adsorbent surfaces such as graphite are known to increase the melting temperature of solid H2, this effect is normally rather small, increasing to 20 Kelvin (K) relative to 14 K in the bulk. An as-yet unidentified phase transition has been observed in a system of H2 adsorbed in a porous, locally graphitic, Saran carbon with sub-nanometer sized pores at temperatures (74-101 K) and pressures ( > 76 bar) well above the critical point of bulk H2 using hydrogen adsorption and neutron scattering experiments. Adsorption data shows a discontinuous pressure jump in the kinetics at 76 bar after nearly an hour of equilibration time, which is identified as an exothermic phase transition. This discontinuity is observed in the 87 K isotherm, but not the 77 K isotherm. At higher pressures, the measured isotherms show greater excess adsorption at 87 K than 77 K. Inelastic neutron scattering measurements also show a striking phase transition, with the amount of high angle scattering (corresponding to large momentum transfer/ large effective mass) increasing by up to a factor of 5 in the novel phase. During the course of the neutron scattering experiment, three of these reversible spectral phase transitions were observed to occur in response to only changes in sample temperature. The novel phase was observed by neutron scattering only at high H2 pressure (123 bar and 187 bar) and temperatures between 74-101 K in the sample of interest, but not at low pressure (30 bar), or in a control activated carbon at 186 bar of H2 pressure. Based on several of the more unusual observations, such as the slow equilibration and the presence of both an upper and lower temperature bound, a reasonable hypothesis is that this phase forms only in the presence of a high concentration of ortho-H2 (nuclear spin S=1). The increase in adsorption with temperature, temperatures which cross the lower temperature bound observed by neutron scattering, indicates that this novel phase is denser. Structural characterization data on the adsorbent shows that it may support a commensurate solid phase denser than those known to exist on graphite at much lower temperatures. Whatever this phase is eventually proven to be, these results show that surfaces can have a more striking effect on hydrogen phases than previously thought.

Keywords: adsorbed phases, hydrogen, neutron scattering, nuclear spin

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Authors: A. Maghari, V. M. Maleki

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In this paper, we present a quantum statistical mechanical formulation from our recently analytical expressions for partial-wave transition matrix of a three-particle system. We report the quantum reactive cross sections for three-body scattering processes 1 + (2,3)-> 1 + (2,3) as well as recombination 1 + (2,3) -> 2 + (3,1) between one atom and a weakly-bound dimer. The analytical expressions of three-particle transition matrices and their corresponding cross-sections were obtained from the three-dimensional Faddeev equations subjected to the rank-two non-local separable potentials of the generalized Yamaguchi form. The equilibrium quantum statistical mechanical properties such partition function and equation of state as well as non-equilibrium quantum statistical properties such as transport cross-sections and their corresponding transport collision integrals were formulated analytically. This leads to obtain the transport properties, such as viscosity and diffusion coefficient of a moderate dense gas.

Keywords: statistical mechanics, nonlocal separable potential, three-body interaction, faddeev equations

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Authors: Abu Afree Andalib, Rafiur Rahman, Md Mezbah Uddin

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The main objective of this work is to anatomize on the various parameters of AGM 88 missile anatomized using FSI module in Ansys. Computational fluid dynamics is used for the study of fluid flow pattern and fluidic phenomenon such as drag, pressure force, energy dissipation and shockwave distribution in water. Using finite element analysis module of Ansys, structural parameters such as stress and stress density, localization point, deflection, force propagation is determined. Separate analysis on structural parameters is done on Abacus. State of the art coupling module is used for FSI analysis. Fine mesh is considered in every case for better result during simulation according to computational machine power. The result of the above-mentioned parameters is analyzed and compared for two phases using graphical representation. The result of Ansys and Abaqus are also showed. Computational Fluid Dynamics and Finite Element analyses and subsequently the Fluid-Structure Interaction (FSI) technique is being considered. Finite volume method and finite element method are being considered for modelling fluid flow and structural parameters analysis. Feasible boundary conditions are also utilized in the research. Significant change in the interaction and interference pattern while the impact was found. Theoretically as well as according to simulation angled condition was found with higher impact.

Keywords: FSI (Fluid Surface Interaction), impact, missile, high viscous fluid, CFD (Computational Fluid Dynamics), FEM (Finite Element Analysis), FVM (Finite Volume Method), fluid flow, fluid pattern, structural analysis, AGM-88, Ansys, Abaqus, meshing, k-omega, turbulence model

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Authors: Pakawhat Khumkhreung, Yottana Khunatorn

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The flow pattern inside rectangular intake air duct of 300 MW lignite coal-fired power plant is investigated in order to analyze and reduce overall inlet system pressure drop. The system consists of the 45-degree inlet elbow, the flow instrument, the 90-degree mitered elbow and fans, respectively. The energy loss in each section can be determined by Bernoulli’s equation and ASHRAE standard table. Hence, computational fluid dynamics (CFD) is used in this study based on Navier-Stroke equation and the standard k-epsilon turbulence modeling. Input boundary condition is 175 kg/s mass flow rate inside the 11-m² cross sectional duct. According to the inlet air flow rate, the Reynolds number of airstream is 2.7x10⁶ (based on the hydraulic duct diameter), thus the flow behavior is turbulence. The numerical results are validated with the real operation data. It is found that the numerical result agrees well with the operating data, and dominant loss occurs at the flow rate measurement device. Normally, the air flow rate is measured by the airfoil and it gets high pressure drop inside the duct. To overcome this problem, the airfoil is planned to be replaced with the other type measuring instrument, such as the average pitot tube which generates low pressure drop of airstream. The numerical result in case of average pitot tube shows that the pressure drop inside the inlet airstream duct is decreased significantly. It should be noted that the energy consumption of inlet air system is reduced too.

Keywords: airfoil, average pitot tube, combustion air, CFD, pressure drop, rectangular duct

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Authors: R. Khenata, T. Djied, R. Ahmed, H. Baltache, S. Bin-Omran, A. Bouhemadou

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We predict structural, phase transition as well as opto-electronic properties of the filled-tetrahedral (Nowotny-Juza) NaZnAs compound in this study. Calculations are carried out by employing the full potential (FP) linearized augmented plane wave (LAPW) plus local orbitals (lo) scheme developed within the structure of density functional theory (DFT). Exchange-correlation energy/potential (EXC/VXC) functional is treated using Perdew-Burke and Ernzerhof (PBE) parameterization for generalized gradient approximation (GGA). In addition to Trans-Blaha (TB) modified Becke-Johnson (mBJ) potential is incorporated to get better precision for optoelectronic properties. Geometry optimization is carried out to obtain the reliable results of the total energy as well as other structural parameters for each phase of NaZnAs compound. Order of the structural transitions as a function of pressure is found as: Cu2Sb type → β → α phase in our study. Our calculated electronic energy band structures for all structural phases at the level of PBE-GGA as well as mBJ potential point out; NaZnAs compound is a direct (Γ–Γ) band gap semiconductor material. However, as compared to PBE-GGA, mBJ potential approximation reproduces higher values of fundamental band gap. Regarding the optical properties, calculations of real and imaginary parts of the dielectric function, refractive index, reflectivity coefficient, absorption coefficient and energy loss-function spectra are performed over a photon energy ranging from 0.0 to 30.0 eV by polarizing incident radiation in parallel to both [100] and [001] crystalline directions.

Keywords: NaZnAs, FP-LAPW+lo, structural properties, phase transition, electronic band-structure, optical properties

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Authors: Sumit Kumar Das, Laishram Ladusingh

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Aim: The aim of the study is to examine the differential of epidemiological transition across fifteen agro-climatic zones of India and its effect on health-seeking behavior. Data and Methods: Unit level data on consumption expenditure on health of India from three decadal rounds conducted by National Sample Survey Organization are used for the analysis. These three rounds are 52nd (1995-96), 60th (2004-05) and 71st (2014-15). The age-adjusted prevalence rate for communicable diseases and non-communicable diseases are estimated for fifteen agro-climatic zones of India for three time periods. Bivariate analysis is used to find out determinants of health-seeking behavior. Multilevel logistic regression is used to examine factors effecting on household health-seeking behavior. Result: The prevalence of communicable diseases is increasing in most of the zones of India. Every South Indian zones, Gujarat plains, and lower Gangetic plain are facing the severe attack of dual burden of diseases. Demand for medical advice has increased in southern zones, and east zones, reliance on private healthcare facilities are increasing in most of the zone. Demographic characteristics of the household head have a significant impact on health-seeking behavior. Conclusion: Proper program implementation is required considering the disease prevalence and differential in the pattern of health seeking behavior. Along with initiation and strengthening of programs for non-communicable, existing programs for communicable diseases need to monitor and supervised strictly.

Keywords: agro-climatic zone, epidemiological transition, health-seeking behavior, multilevel regression

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Authors: Neslihan Beyazit, Sahin Bayraktar, Cahit Demetgul

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Transition metal ions have an important role in biochemistry and biomimetic systems and may provide the basis of models for active sites of biological targets. The presence of copper(II), iron(II) and zinc(II) is crucial in many biological processes. Tetradentate N2O2 donor Schiff base ligands are well known to form stable transition metal complexes and these complexes have also applications in clinical and analytical fields. In this study, we present salient structural features and the details of cathecholase activity of Fe(II) complex of a new Schiff Base ligand. A new asymmetrical N2O2 donor Schiff base ligand and its Fe(II) complex were synthesized by condensation of 4-nitro-1,2 phenylenediamine with 6-formyl-7-hydroxy-5-methoxy-2-methylbenzopyran-4-one and by using an appropriate Fe(II) salt, respectively. Schiff base ligand and its metal complex were characterized by using FT-IR, 1H NMR, 13C NMR, UV-Vis, elemental analysis and magnetic susceptibility. In order to determine the kinetics parameters of catechol oxidase-like activity of Schiff base Fe(II) complex, the oxidation of the 3,5-di-tert-butylcatechol (3,5-DTBC) was measured at 25°C by monitoring the increase of the absorption band at 390-400 nm of the product 3,5-di-tert-butylcatequinone (3,5-DTBQ). The compatibility of catalytic reaction with Michaelis-Menten kinetics also investigated by the method of initial rates by monitoring the growth of the 390–400 nm band of 3,5-DTBQ as a function of time. Kinetic studies showed that Fe(II) complex of the new N2O2 donor Schiff base ligand was capable of acting as a model compound for simulating the catecholase properties of type-3 copper proteins.

Keywords: catecholase activity, Michaelis-Menten kinetics, Schiff base, transition metals

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Authors: Ji-yang Yu, Dan Huang, Guo-ping Feng, Xin Li, Lu-yuan Wang

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The navigation satellite network, especially the Beidou MEO Constellation, can relay data effectively with wide coverage and is applied in navigation, detection, and position widely. But the constellation has not been completed, and the amount of satellites on-board is not enough to cover the earth, which makes the data-relay disrupted or delayed in the transition process. The data-relay function needs to tolerant the delay or disruption in some extension, which make the Beidou MEO Constellation a delay/disruption-tolerant network (DTN). The traditional DTN designs mainly employ the relay table as the basic of data path schedule computing. But in practical application, especially in critical condition, such as the war-time or the infliction heavy losses on the constellation, parts of the nodes may become invalid, then the traditional DTN design could be useless. Furthermore, when transmitting the critical message in the navigation system, the maximum priority strategy is used, but the nodes still inquiry the relay table to design the path, which makes the delay more than minutes. Under this circumstances, it needs a function which could compute the optimum data path on-board in real-time according to the constellation states. The on-board critical message transmission design for navigation satellite delay/disruption-tolerant network (DTN) is proposed, according to the characteristics of navigation satellite network. With the real-time computation of parameters in the network link, the least-delay transition path is deduced to retransmit the critical message in urgent conditions. First, the DTN model for constellation is established based on the time-varying matrix (TVM) instead of the time-varying graph (TVG); then, the least transition delay data path is deduced with the parameters of the current node; at last, the critical message transits to the next best node. For the on-board real-time computing, the time delay and misjudges of constellation states in ground stations are eliminated, and the residual information channel for each node can be used flexibly. Compare with the minute’s delay of traditional DTN; the proposed transmits the critical message in seconds, which improves the re-transition efficiency. The hardware is implemented in FPGA based on the proposed model, and the tests prove the validity.

Keywords: critical message, DTN, navigation satellite, on-board, real-time

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Authors: Konrad Pietrykowski, Michal Bialy, Pawel Karpinski, Radoslaw Maczka

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The nozzle is an element of the rocket engine in which the conversion of the potential energy of gases generated during combustion into the kinetic energy of the gas stream takes place. The design parameters of the nozzle have a decisive influence on the ballistic characteristics of the engine. Designing a nozzle assembly is, therefore, one of the most responsible stages in developing a rocket engine design. The paper presents the results of the simulation of three types of rocket propulsion nozzles. Calculations were made using CFD (Computational Fluid Dynamics) in ANSYS Fluent software. The next types of nozzles differ in shape. The analysis was made of a conical nozzle, a bell type nozzle with a conical supersonic part and a bell type nozzle. Calculation results are presented in the form of pressure, velocity and kinetic energy distributions of turbulence in the longitudinal section. The courses of these values along the nozzles are also presented. The results show that the cone nozzle generates strong turbulence in the critical section. Which negatively affect the flow of the working medium. In the case of a bell nozzle, the transformation of the wall caused the elimination of flow disturbances in the critical section. This reduces the probability of waves forming before or after the trailing edge. The most sophisticated construction is the bell type nozzle. It allows you to maximize performance without adding extra weight. The bell type nozzle can be used as a starter and auxiliary engine nozzle due to its advantages. The project/research was financed in the framework of the project Lublin University of Technology-Regional Excellence Initiative, funded by the Polish Ministry of Science and Higher Education (contract no. 030/RID/2018/19).

Keywords: computational fluid dynamics, nozzle, rocket engine, supersonic flow

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Authors: K. Bhojnadh, M. Fiddler, D. Cheshire

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An investigation into the Kutta effect on the trailing edge of a subsonic aerofoil was conducted which led to an analysis using Ansys Fluent to determine the effect of flow separation over a NACA 0012 aerofoil. This aerofoil was subjected to oscillations to create an unsteady flow over the aerofoil, therefore, creating turbulence, with unsteady aerodynamics playing a key role to determine the flow regimes when the aerofoil is subjected to different angles of attack along with varying Reynolds numbers. Many theories were evolved to determine the flow parameters of a 2-D aerofoil in these unsteady conditions because they behave unpredictably at the trailing edge when subjected to a different angle of attack. The shear area observed in the boundary layer at the trailing edge tends towards an unsteady turbulent flow even at small angles of attack, creating drag as the flow separates, reducing the aerodynamic performance of aerofoil. In this paper, research was conducted to determine the effect of Kutta circulation over the aerofoil and the effect of that circulation in reducing the effect of pressure and boundary layer distribution over the aerofoil. The effect of circulation is observed by using Ansys Fluent by using varying flow parameters and differential schemes to observe the flow behaviour on the aerofoil. Initially, steady flow analysis was conducted on the aerofoil to determine the effect of circulation, and it was noticed that the effect of circulation could only be properly observed when the aerofoil is subjected to oscillations. Therefore, that was modelled by using Ansys user-defined functions, which define the motion of the aerofoil by creating a dynamic mesh on the aerofoil. Initial results were observed, and further development of the dynamic mesh functions in Ansys is taking place. This research will determine the overall basic principles of unsteady flow aerodynamics applied to the investigation of Kutta related circulation, and gives an indication regarding the generation of vortices which is discussed further in this paper.

Keywords: circulation, flow seperation, turbulence modelling, vortices

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Authors: Azhar Ulhaq, Zubair Yameen, Almas Anjum

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Frequency behaviour of self-excited induction generator (SEIG) wind turbines during control mode transition from grid connected to islanded mode is studied in detail. A robust control scheme for frequency regulation based on combined action of STATCOM, energy storage system (ESS) and pitch angle control for wind powered microgrid (MG) is proposed. Suggested STATCOM controller comprises a 3-phase voltage source converter (VSC) that contains insulated gate bipolar transistors (IGBTs) based pulse width modulation (PWM) inverters along with a capacitor bank. Energy storage system control consists of current controlled voltage source converter and battery bank. Both of them acting simultaneously after detection of island compensates for reactive and active power demands, thus regulating frequency at point of common coupling (PCC) and also improves load stability. STATCOM integrates at point of common coupling and ESS is connected to microgrids main bus. Results reveal that proposed control not only stabilizes frequency during transition duration but also minimizes sudden frequency imbalance caused by load variation or wind intermittencies in islanded operation. System is investigated with and without suggested control scheme. The efficacy of proposed strategy has been verified by simulation in MATLAB/Simulink.

Keywords: energy storage system, island, wind, STATCOM, self-excited induction generator, SEIG, transient

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Authors: Cheng-Cao Sun, Shu-Jun Li, De-Jia Li

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Through analysis of a published micro-array-based high-throughput assessment, we discovered that miR-1275 was markedly down-regulated in nasopharyngeal carcinoma (NPC) tissues. However, little is known about its effect and mechanism involved in NPC development and progression. In this study, we investigated the role of miR-1275 on the development of NPC. The results indicated that miR-1275 was significantly down-regulated in primary NPC tissues, and very low levels were found in NPC cell lines. Ectopic expression of miR-1275 in NPC cell lines significantly suppressed cell growth as evidenced by cell viability assay and colony formation assay, through inhibition of HOXB5. In addition, miR-1275 suppresses G1/S transition through inhibition of HOXB5. Further, oncogene HOXB5 was revealed to be a putative target of miR-1275, which was inversely correlated with miR-1275 expression in NPC. Collectively, our study demonstrates that as a tumor suppressor, miR-1275 played a pivotal role on NPC through inhibiting cell proliferation, and suppressing G1/S transition by targeting oncogenic HOXB5.

Keywords: microRNA-1275 (miR-1275), HOXB5, nasopharyngeal carcinoma, proliferation

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Authors: Andrey Makarov

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This article will focus on the development of antitrust policy in transition economies in the context of preventing explicit and tacit collusion. Experience of BRICS, CIS (Ukraine, Kazakhstan) and CEE countries (Bulgaria, Hungary, Latvia, Lithuania, Poland, Romania, Slovakia, Slovenia, Czech Republic, Estonia) in the creation of antitrust institutions was analyzed, including both legislation and enforcement practice. Most of these countries in the early 90th were forced to develop completely new legislation in the field of protection of competition and it is important to compare different ways of building antitrust institutions and policy results. The article proposes a special approach to evaluation of preventing collusion mechanisms. This approach takes into account such enforcement problems as: classification problems (tacit vs explicit collusion, vertical vs horizontal agreements), flexibility of prohibitions (the balance between “per se” vs “rule of reason” approaches de jure and in practice), design of sanctions, private enforcement challenge, leniency program mechanisms, the role of antitrust authorities etc. The analysis is conducted using both official data, published by competition authorities, and expert assessments. The paper will show how the integration process within the EU predetermined some aspects of the development of antitrust policy in CEE countries, including the trend of the use of "rule of reason" approach. Simultaneously was analyzed the experience of CEE countries in special mechanisms of government intervention. CIS countries in the development of antitrust policy followed more or less original ways, without such a great impact from the European Union, more attention will be given to Russian experience in this field, including the analysis of judicial decisions in antitrust cases. Main problems and challenges for transition economies in this field will be shown, including: Legal uncertainty problem; Problem of rigidity of prohibitions; Enforcement priorities of the regulator; Interaction of administrative and criminal law, limited effectiveness of criminal sanctions in the antitrust field; The effectiveness of leniency program design; Private enforcement challenge.

Keywords: collusion, antitrust policy, leniency program, transition economies, Russia, CEE

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Authors: Sourina Bej

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Since the process of decolonization in 1940, several countries in South Asia have witnessed intra-state conflicts owing to ineffective political governance. The conflicts have remained protracted as the countries have failed to make a holistic transition to a democratic state. Nepal is one such South Asian country facing a turmultous journey from monarchy to republicanism. The paper aims to focus on the democratic transition in the context of Nepal’s political, legal and economic institutions. The presence of autocratic feudalistic and centralised state structure with entrenched socio-economic inequalities has resulted in mass uprising only to see the country slip back to the old order. Even a violent civil war led by the Maoists could not overhaul the political relations or stabilize the democratic space. The paper aims to analyse the multiple political, institutional and operational challenges in the implementation of the peace agreement with the Maoist. Looking at the historical background, the paper will examine the problematic nation-building that lies at the heart of fragile peace process in Nepal. Regional dynamics have played a big role in convoluting the peace-building. The new constitution aimed at conflict resolution brought to the open, deep seated hatred among different ethnic groups in Nepal. Apart from studying the challenges to the peace process and the role of external players like India and China in the political reconstruction, the paper will debate on a viable federal solution to the ethnic conflict in Nepal. If the current government fails to pass a constitution accepted by most ethnic groups, Nepal will remain on the brink of new conflict outbreaks.

Keywords: democratisation, ethnic conflict, Nepal, peace process

Procedia PDF Downloads 255