bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the magnet aspect ratio on the dynamic stiffness of a rotating superconducting magnetic bearing
Authors: Espenhahn Tilo , Wunderwald Florian , Möller Marcel , Sparing Maria , Hossain Mahmud , Fuchs Günter , Abdkader Anwar , Cherif Chokri , Nielsch Kornelius , Hühne Ruben
Published: October 2019

Rotating superconducting bearings promise great potential in applications due to their frictionless operation. However, these bearings show a lower dynamic stiffness and damping coefficient compared to ball bearings. In this paper we studied a bearing consisting of a fixed YBCO ring and a rotating magnet above the superconductor. The influence of the magnet aspect ratio on the dynamic stiffness of the bearing was investigated in order to find an optimized size. To change the aspect ratio, we kept the inner diameter of the ring constant and reduced the outer diameter while increasing the ring height. In addition to these magnets, one magnet with a reduced cross-sectional area was studied. The aspect ratio selection was based on preliminary magnetic flux density simulations, which compared the magnetic flux density distribution and the potential radial force for different aspect ratios.

To conduct the measurements, the field-cooled magnets were displaced in a lateral direction and then released, resulting in a damped oscillation. The dynamic stiffness constants were calculated for each bearing from the relation of three axis acceleration measurements for different field cooling heights. The comparison of the stiffness constants for the different bearings revealed an optimal aspect ratio for the given YBCO ring. This optimum is almost independent from the cooling height. The comparison between the two magnet rings with similar diameters and different heights was similar for the bearing characteristics at a low cooling height, whereas a significant reduction of stiffness was observed with a larger cooling distance. The difference is bigger for the magnet with a reduced height. The optimal aspect ratio as well as the stiffness dependence on the cross-sectional area was confirmed by simulations of the magnetic flux density distribution.
Four-point transient potential drop measurements on metal plates
Authors: Persvik Øyvind , Zhang Zhiliang
Published: October 2019

The transient potential drop method is based on measurement of the transient voltage on the surface of a conductor due to the injection of a pulsed current. In this paper, we consider an approximate analytical model for four-point transient potential drop measurements on plates that are thin compared to the probe separation. Experimental results show good agreement with the theory for measurements made on non-magnetic and ferromagnetic plates when an exponentially rising pulsed current is used as a source. To demonstrate possible applications of the theory we consider measurement of the conductivity and relative permeability of the materials as well as plate thickness.
Terahertz shielding properties of aero-GaN
Authors: Braniste Tudor , Zhukov Sergey , Dragoman Mircea , Alyabyeva Liudmila , Ciobanu Vladimir , Aldrigo Martino , Dragoman Daniela , Iordanescu Sergiu , Shree Sindu , Raevschi Simion , Adelung Rainer , Gorshunov Boris , Tiginyanu Ion
Published: October 2019

The electrodynamic properties of the first aero-material based on compound semiconductor, namely of Aero-GaN, in the terahertz frequency region are experimentally investigated. Spectra of complex dielectric permittivity, refractive index, surface impedance are measured at frequencies 4–100 cm−1 and in the temperature interval 4–300 K. The shielding properties are found based on experimental data. The aero-material shows excellent shielding effectiveness in the frequency range from 0.1 to 1.3 THz, exceeding 40 dB in a huge frequency bandwidth, which is of high interest for industrial applications. These results place the aero-GaN among the best THz shielding materials known today.
Bumblebee hair motion in electric fields
Authors: Koh KL , Montgomery C , Clarke D , Morley EL , Robert D
Published: October 2019

Bees have been observed to detect and learn the presence of weak electric fields in various behavioural experiments in the lab. The electro-sensitivity of bumblebees has also been suggested to be important for pollination. However, the structure and function of electro-sensory organs are yet to be described. Bees, like other arthropods, are known to have evolved various mechanoreceptors. Antennae and hairs have mechanosensory functions and have been shown to respond to weak electric fields. Current proposals posit that hairs and antennae can act as electromechanical sensors. To investigate this hypothesis, the mechanical response of bumblebee hairs stimulated by an electric field was measured using microscanning laser Doppler vibrometry. Hair vibration velocity is shown to be proportional to charge triboelectrically deposited on the bee and the effect of polarisation charge is seen to be negligible. Hair motion due to acoustic stimuli is also measured and compared to hair electromechanical response. Preliminary results show that the electro-sensitivity of charged bee hairs is comparable to hair sensitivity to acoustic stimuli.
Fluid Viscosity and Corresponding Effects on Fluid flow, Velocity Magnitude and Electric Field Distribution in Electrohydrodynamic Jetting.
Authors: Aramide Babatunde , Jayasinghe Suwan , Ventikos Yiannis
Published: October 2019

The phenomenon of electrohydrodynamic (EHD) jetting is affected by both the flow and electric properties of the dielectric fluid. A computational fluid dynamics (CFD) approach has been used to analyse the resultant effect of fluid viscosity on EHD flows. This study looks at the unique effect of fluid viscosity on the flow profile, velocity magnitude and the electric field distribution. It is very difficult to experimentally study these relationships, but CFD provides insights that can open the world of Electrohydrodynamics to new levels of applications; as this will give an idea of how to manipulate the jet formation. Viscosity has been highlighted as one of the key parameters that aid jet elongation and stability. Therefore, the necessity to study its role. Most studies have been carried out experimentally, but this paper provides computation insights. To solve the multiphase problem, a finite volume method using the Volume of Fluid approach for capturing the shape of the interface was used for the investigation. The leaky dielectric model which describes the process solves the combination of the Charge Transport Model and Navier-Stokes equations simultaneously. The transient liquid-gas interface tracking was achieved using the VOF technique. Among many other features observed, the results showed that it takes more time for the electric field to overcome the opposing surface tension of the solution at higher viscosity than at lower viscosity. Higher electric field magnitudes/strength were observed for the fluid of lower viscosity than that of the higher viscosity. Also, an increase in the viscosity reduces the droplet size/jet diameter.
A kinetic model for the electrostatic spark discharge in atmospheric-pressure air
Authors: Ohsawa A
Published: October 2019

This paper presents a 0-D kinetic model of electrostatic spark discharges consisting of the time-dependent Boltzmann equation of electrons, a discharge-circuit equation, and heavy particles’ kinetic equations to investigate the energy-transfer mechanisms from the electrostatic energy given to the energy of gases by the spark discharge. In this report, the model is applied to the discharges in atmospheric-pressure air under optimum conditions corresponding for the minimum ignition energies of the typical flammable gases, hydrogen, ethylene and propane, in three types of explosion groups for gases.
Can Electrostatic Discharge Sensitive electronic devices be damaged by electrostatic fields?
Authors: Smallwood Jeremy
Published: October 2019

In recent years the susceptibility of ElectroStatic Discharge Sensitive devices (ESDS) to electrostatic fields has been questioned. This paper proposes that very high impedance voltage sensitive ESDS such as MOSFETs or MOS capacitors can be damaged due external field changes without making contact with other conductors in the presence of the field. A simple electronic model is proposed. In a practical evaluation of this risk, discharges are demonstrated to occur due changing external fields, as a result of breakdown of a voltage sensitive structure in a high impedance circuit with one terminal continuously grounded.
Charge distribution and discharge current analysis with charged connector pins
Authors: Tamminen Pasi
Published: October 2019

Electronic components and electromechanics can get static charges during handling and discharge on a printed circuit board when assembled. This study focuses on charged connector metal pins with less than 2 pF source capacitance. A charge distribution, rise time, and shape of the discharge current waveform is studied by using co-simulations between frequency domain finite element method and SPICE time domain circuits. Results show that the current rise time can be less than 10 ps and mainly depends on the inductance of the discharge path when the initial charging voltage is constant. The frequency response of the 3D object defines the shape of the discharge current waveform together with the series inductance and resistance of the discharge path.
Measurement of electric fields of charged spray clouds of conductive liquids in free space and in a conductive vessel
Authors: Baumann F , Esslinger J , Möckel D , Thedens M , Losert O
Published: October 2019

The process of spraying liquids generated electrical charges. The question therefore arises as to whether this electrostatic charge represent an ignition hazard when an explosive mixture is present. This hazard occurs when cleaning vessels, in which an explosive mixture is formed by residues of easily flammable liquids or the cleaning medium itself. Although measurement techniques and methods exist for detecting this electrostatic charging process, they have not been sufficiently scientifically proven. The Chilworth JCI 131 adverse conditions field meter is to be used to measure the electrostatic charging of sprayed liquids. It shall be validated by measuring the electric field strength of a flat spray water jet in low-pressure range (8 bar) charged by contact charging and accumulation of free electrons of a commercial, insulated arranged electrostatic spraying system (up to - 90 kV). A flat-jet nozzle is selected which atomizes the spray jet, which serves as the measuring surface, sufficiently large. This arrangement is further investigated in a 1 m3 stainless steel IBC. The investigations presented are part of a project aiming to extend the scope of the German Technical Rules for Hazardous Substances (TRGS) of TRGS 727, which regulate avoiding ignition hazards resulting from electrostatic charging. The aim is to reach an understanding that allows provisions for safe cleaning of “small” and “medium-sized” containers up to 50 m3. This project is funded by DGUV (German Social Accident Insurance) and partners from the industry.
Optimization of parameters of designed and developed hand-held electrostatic sprayer and its performance evaluation for herbal pesticides
Authors: Patel M K , Kumar A , Kumar P , Jangra A , kumar A
Published: October 2019

Electrostatic force field has been exploited in the design and development of a handheld air-assisted electrostatic sprayer for herbal pesticides. Electrostatic spraying is a novel approach for agricultural pesticides applications to increase the mass transfer efficiency, pesticide bio-efficacy, uniform deposition, maximum canopy coverage and liquid pest to reach the hidden areas and underside of the target by reducing the drift of active ingredients of pesticides from the target. A new air-assisted electrostatic sprayer has been designed and developed for small scale farms with a specific focus on rural developing economies. In this work, experiments were carried out with four types of herbal pesticides and one chemical pesticide to evaluate and compare the performance of developed electrostatic sprayer. The results are characterized in terms of depended variable i.e. charge-to-mass ratio by varying independent variables such as applied voltage, air pressure, conductivity and density of liquid. The droplets are charged more than 8 mC/kg with an applied voltage of 1.5 kV at a flow rate of 110 ml/min and air pressure of 40 psi which is more than desirable to achieve the wraparound effect. This nozzle is light weight, highly efficient, reduces pesticide use and human health risks, and eco-friendly.
Monte-Carlo simulations of electrostatic self-charging of tritiated tungsten and beryllium particles
Authors: Dougniaux Grégoire , Sow Mamadou , Peillon Samuel , Grisolia Christian , Gensdarmes Francois
Published: October 2019

The electrostatic self-charging rate of tokamak dust is investigated using Geant4, a toolkit for the simulation of the passage of particles through matter. To do so, the particles geometrical characteristics, the β disintegration energy spectrum and the deepness of tritium infusion are taken into account. The investigated materials are tungsten and beryllium, the plasma facing components (PFC) of ITER, considered as spherical particles from 20 nm to 200 μm in diameter, both tritiated. Two cases of tritium distribution in the particles are examined. On the one hand, tritium is homogeneously distributed over the whole sphere; on the other hand, tritium is homogeneously distributed within the external 100 nm layer of the sphere. The self-charging rate is assessed through the calculation of the particle exiting electron rate. Based on a tritium inventory of 10 GBq/g, relevant for ITER tokamak environment, our results show that, for a single tungsten or beryllium particle of 10 μm in diameter, the self-charging rate when the tritium is homogeneously distributed within the whole sphere is respectively 2.4 and 1.9 positive elementary charges per second. In the configuration where the tritium absorption is confined in the external 100 nm layer, the charge magnitude raises up to 37.1 and 8.4 respectively.
Lightning in other planets
Authors: Helling Christiane
Published: October 2019

More than 4000 planet are known that orbit stars other than our Sun. Many harbor a dynamic atmosphere that is cold enough that cloud particles can form in abundance. The diversity of exoplanets leads to differences in cloud coverage depending on global system parameters. Some planets will be fully covered in clouds, some have clouds on the nightside but are largely cloud-free on the dayside. These cloud particles can easily be charged and lightning discharges will occur in cloudy, dynamic exoplanet atmosphere. Lightning supports a Global Electric Circuit (GCE) on Earth and we argue that exoplanet may develop a GCE in particular if parts of the exoplanet atmospheres can remain cloud free.
A Modified Maxwell Garnett Model: Hysteresis in phase change materials
Authors: Green Nicolas G , Fang Xu
Published: October 2019

The dielectric properties of materials undergoing phase transitions are key to a number of modern and developing technologies, particularly when hysteresis is demonstrated in the response. This paper presents a modified Maxwell Garnett model for analysing electromagnetic hysteresis, using an asymmetric effective medium approximation to describe intermediate states in the phase change, establishing a link between effective medium and hysteresis analysis. The model has few input parameters and provides a phenomenological approach to describing electromagnetic hysteresis in various phase change materials.
Improved light scattering measurement with microscopy data for nanoparticle number-based size distribution
Authors: Caebergs T , Sebaïhi N , Pétry J
Published: October 2019

Size is the key feature of nanoparticle properties. Nanoparticle size distribution can be measured by microscopy technique and light scattering posterior to a separation technique. Discrepancies can be observed, especially in the case of polydisperse samples. Microscopy is more precise for size and shape measurement, while light scattering provides better information about concentration. An experiment is set up to investigate the feasibility of bringing comparability of Asymmetrical Flow Field-Flow Fractionation followed by Multi-Angle Light Scattering and AFM measurements. A sample made from a mixture of stock samples is built, after detailed characterisation of the stock samples. By obtaining comparability of MALS and AFM measurements, a new way to calibrate MALS instrument without the need for reference material is opened: using aliquots of the sample itself as a reference.
Cytotoxicity of hyaluronic acid coated chitosan nanoparticles containing nitric oxide donor against cancer cell lines
Authors: Pelegrino M T , Baldi C , Souza A C S , Seabra A B
Published: October 2019

The incidence and mortality rates of all types of cancer have a global burden. The lack of specificity of chemotherapy is one of the major problems in cancer treatment and it is related with moderate to severe adverse effects. CD44 is a protein overexpressed in certain types of cancer cells and can be used as an anchor of attachment for nanoparticles decorated with hyaluronic acid (HA). HA is a natural polymer with high affinity for CD44 receptors. In this work, chitosan nanoparticles (CS NPs) were coated with HA to delivery nitric oxide (NO) donor to cancer cells. NO is a small molecule involved in several physiological processes and it has cytotoxicity against cancer cells. HA-coated and uncoated NO-releasing CS NPs were synthesized and characterized by different techniques. Uncoated and HA-coated NO-releasing CS NPs have hydrodynamic diameters of 142.80 ± 2.22 nm and 170.80 ± 0.14 nm, respectively, polydispersity index of 0.282 ± 0.010 and 0.37 ± 0.04, respectively, and a zeta potential values of + 25.20 ± 0.85 mV and + 15.60 ± 0.15 mV, respectively. As expected, the presence of HA layer on the surface of NO-releasing CS NPs increased hydrodynamic size ca. 20%. The encapsulation efficiency of the NO donor into CS NPs was found to be higher than 90%. The kinetic of NO release from uncoated and HA-coated CS NPs has two distinct phases, an initial burst followed by the establishment of a plateau, with a maximum of NO released at 40 mmol·L−1. At this concentration, NO is expected to have cytotoxic effects. The cytotoxicity of uncoated and HA-coated NO releasing CS NPs showed a concentration-dependent toxicity against human prostatic carcinoma (PC-3) and human uterine cervix carcinoma (HeLa) cell lines. Taken all together, uncoated and HA-coated NO-releasing CS NPs might find important biomedical applications, including cancer in treatment.
Empirical analysis of regulative risk assessment processes of nanomaterials under the Toxic Substances Control Act (TSCA) and European Union regulation concerning the Registration, Evaluation, Authorization and restriction of Chemicals (REACH)
Authors: Miettinen Mirella
Published: October 2019

An empirical analysis of regulative risk assessment processes of nanomaterials under the Toxic Substances Control Act (TSCA) and Regulation (EC) No 1907/2006 of the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) was performed. Risk assessment that has regulatory applicability must be based on legally binding norms, and “process” refers here to the approach taken by the regulatory bodies in the U.S. and the EU to implement those norms. Data consisted of the number of notifications/dossiers for the nanomaterials or the substances that contain also nanoform received by the Environmental Protection Agency (EPA) and the European Chemicals Agency (ECHA), and decisions of the Agencies. The data was analyzed using descriptive statistics and classification. The analysis focused on the challenges in detection of nanomaterials and information collection that are the core functions of risk-based regulation and may create dissimilar compliance requirements for companies. The results show that a loophole in detection of nanomaterials and information collection on them exists in the EU under the REACH, and that regulative risk assessment processes performed by the ECHA and EPA under the REACH and the TSCA, respectively, may result in different compliance requirements for companies. The differences arise partly from the legal provisions that determine the authority and obligations of the Agencies, but also from the decision making practices adopted by the Agencies.
Proton-induced radiation effects in the I/O blocks of an SRAM-based FPGA
Authors: Placinta V.M. , Cojocariu L.N. , Ravariu C.
Published: October 2019

This work presents an experimental study of the proton-induced failures in the Input/Output blocks and in the associated configuration of an SRAM-based Field Programmable Gate Array (FPGA) using a single inverter ring oscillator-configuration. The tests have been done on the KINTEX-7 FPGAs, which were exposed to a 35 MeV proton beam. The cross-sections for 3 classes of single-event effects—in an I/O user logic with a low configuration memory usage of less than 1%—have been determined to be: 2.22−1+1.4⋅ 10−11cm2/device, 1.53 ⋅ 10−11cm2/device (the upper limit) and 0.97−0.6+1⋅ 10−11cm2/device, respectively. The conclusions and the probable impact of the results on the end-application are presented.
Twenty-first century technology of combating wildfire
Authors: De D K , Olawole O C , Joel E S , Ikono U I , Oyedepo S O , Olawole O F , Obaseki O , Oduniyi I , Omeje M , Ayoola A A , Usikalu M R , Omotosho T V , Bolujo E O , Ilo I P
Published: October 2019

Wildfire causes havoc and serious destruction of forest resources and wildlife. It also causes occasionally serious damages to human lives and properties. Current technology of fighting wildfire employs fire retardant chemicals, which pollute the environment seriously, and damages both wild and aquatic lives. Based on the new novel technology, it is possible that in the near future the industrial emissions that pollute the environments and cause health problems would be completely captured in frozen solid forms of emissions products. One of these is the frozen carbon dioxide, which is known as dry ice, which would be available than in hundreds of millions of tons in any country. Cost analysis shows that the power and cement industries would significantly benefit by selling the dry ice captured using the technology, just at $0.07 per kg. The present paper discusses the new technology of applying dry ice that would thus be abundantly available in fighting a wildfire. The paper discusses how the new technology would be by far superior to current technology that employs fire retardant chemicals in terms of environmental protection and the cost-effectiveness over the current technology.
Wind energy generation from Nigeria continental shelf: A review
Authors: Attabo A A , Ajayi O O , Oyedepo S O
Published: October 2019

The menace of global warming and increase of green-house gases have motivated many countries to embrace renewable energy sources as an alternative to fossil fuels. Some of the means by which sustainable energy is tapped are solar, biofuel, and wind. Wind energy have been around for quite some time and the power in the wind have been harnessed on land. However, due to some constraints related to land use, visual impacts and turbulence induced by buildings and trees, offshore wind farms have been engaged to provide quality alternative to onshore wind energy. This study reviews various works that have been done in the offshore wind development and tries to make a case for the generation of electricity from this type of renewable energy source to boost the nation’s electricity demand. Work done in offshore energy assessment, wake models, offshore turbine layout, future innovation in offshore wind turbine and Nigeria onshore energy scenario were reviewed. To speed up development of offshore wind energy in Nigeria, recommendation was made for government to invest in wind energy research, industries that operate in the offshore region should be willing to share meteorological data with researchers and tertiary institutions should encourage student to work on “issue-based” projects like proffering solution to the energy deficit crisis in the country.
Issues and Challenges Involved In Green Building Concept Innovations Adoption In Construction Practice
Authors: Amusan Lekan M , Oluwakorede Michael , Clement Oloke , Adegbenjo Adelakun , Rishi Garba
Published: October 2019

Green concept is globally creating impact with diverse application at various facet of human endeavour. The concept involved the practice whereby energy is utilized in a way that it would not jeopardise continuity of energy usage in the environment. The aim of this study is to explore the issues and challenges that surround the adoption of green concept in Nigeria focusing on built environment with a view to enhancing the rate of adoption of the concept for an increased healthy environment. The study adopted convenience sampling method to pick the population for the study, which comprised of picking construction companies that engaged on a project that involved green building features. Population frame of 250 professionals that are registered with professional bodies that cut across 20 selected construction firms was used for the study. A structured questionnaire designed in Likert scale of 1 to 5 was distributed among 50 respondents for data collation. The data was later processed using content analysis, descriptive statistics and relative agreement index. Data was collated on parameters that include evaluation of existing issues and challenges involved in green building concept innovations adoption in construction practice, current green concept practice in construction, challenges involved in adoption of green concept in construction, critical issues involved in green concept adoption, drivers for success in the adoption of green concepts in construction, challenges involved in adoption of green concept in construction. Innovative illustrations of integration of green concepts in buildings. Mean Item Score was used with relative agreement index, this was used to rate the perception of respondents on parameters calibrated for respondents to answer. Categorical regression analysis was used to carry out comparative analysis of respondents’ submission on success factors that influences the adoption of green building concept and challenges involved in the adoption of green building. Some other parameters were further explored, they include, innovative approach to sustainable construction practice and perspectives to green building practice. The analysis of the study brought to fore factors to be taken into consideration for effective adoption of green building concept. The challenges such as thought reengineering and philosophical and cultural adjustment need to be further harnessed for people to leave the built environment better than it was met.
Fabrication of P3HT: PCBM bulk heterojunction organic solar cell
Authors: Kesinro R. O. , Boyo A.O. , Akinyemi M. L. , Mola G. T.
Published: October 2019

The fabrication of organic solar cells (OSCs) employing solution processing has proven to be a convenient method to guarantee the fabrication of OSCs at low cost and large-scale production. This manuscript demonstrates the successful fabrication of TFOSC with device structure: poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS)/poly (3-hexylthiophene) (P3HT): [6, 6]-phenyl-C61-butyric acid methyl ester (PCBM)/lithium fluoride (LiF)/aluminium (Al) under ambient conditions. An overall power conversion efficiency of 3.25% and charge carrier mobility of 1.22e−2 cm v s−1 was obtained and PEDOT: PSS was beneficial in improving the charge transport processes in the preparation of organic solar cells.
Energy poverty and environmental sustainability in Nigeria: an exploratory assessment
Authors: Nwozor Agaptus , Oshewolo Segun , Ogundele Oluwaseun
Published: October 2019

Energy constitutes an indispensable catalyst for sustainable socio-economic development. The imperative of energy security is highlighted by the pervasive energy poverty that characterizes developing countries, especially Nigeria. Despite being a major oil producer and having four refineries, Nigeria imports 90 percent of its domestically needed refined petroleum products. Similarly, Nigeria requires about 98,000 megawatts (MW) to achieve national electricity security. However, its thermal and hydropower stations have a combined installed capacity of only 12,522MW but generate between 3,000MW and 4,000MW and sometimes less than 3,000MW. The electricity challenge is deepened by fluctuations. The implications of this suboptimal power generation include: only 40 percent of Nigeria’s 193 million population have access to electricity, erratic nature of electricity supply and the long hours of power outages. Thus, Nigeria can be categorized as an energy poor country. The major goal of this paper is to assess the link between energy poverty and environmental sustainability given that households must take alternative steps to bridge energy gaps that impact them. It further evaluates the opportunities and barriers to energy security and holds that the untapped potentials, especially among renewable energy resources, hold the key to sustainable energy development to tackle energy poverty in Nigeria.
The Future of Renewable Energy for Electricity Generation in sub-Saharan Africa
Authors: Adedeji Paul A. , Akinlabi Stephen , Madushele Nkosinathi , Olatunji Obafemi
Published: October 2019

Energy transition in the last decade has experienced increased quota of renewable energy in the global energy mix. In sub-Saharan Africa (SSA), the transition from the fossil fuel to the renewable energy source has been gradual. The state of renewable energy in the region in the next decade is the focus of this study. This study uses a single-layer perceptron artificial neural network (SLP-ANN) to backcast from 2015 to 2006 and forecast from 2016 to 2020 the percentage of renewable energy for electricity generation, exempting the hydropower in the energy mix of the SSA based on historical data. The backcast percentage renewable energy mix was evaluated using known statistical metrics for accuracy measures. The root mean square error (RMSE), mean absolute deviation (MAD) and mean absolute percentage error (MAPE) obtained were 0.29, 0.18, and 14.69 respectively. The result shows possibility of an increase in the percentage of renewable energy in the electricity sector in the region. In 2020, the percentage of renewable energy in sub-Saharan region is expected to rise to 4.13% with exclusion of the hydropower. With government policies encouraging the growth of the renewable energy as a means of power generation in the region, the predicted percentage and even more can be realized.
Effect of Chemicals and Cations on the Activity of Partially Purified alpha amylase produced by Aspergillus niger
Authors: Atolagbe O M , Ajayi A A , Olasehinde G I
Published: October 2019

Amylases are one of the most important enzymes used in the industry. They are responsible for the hydrolysis of starch and glycogen. This research aimed to investigate the effect of cations (Ca2+ and K+) and chemicals (EDTA and HgCl2) on alpha amylase activity. Alpha amylase was produced by Aspergillus niger under submerged fermentation conditions in a basal salt medium. The enzyme was partially purified with activated carbon which gave a 1.57 purification fold. The effects of ethylene diamine tetratacetic acid (EDTA), mercuric chloride (HgCl2), Calcium ion (Ca2+) and Potassium ion (K+) on the partially purified enzymes were then investigated. The enzyme was inhibited to varying degrees by EDTA and HgCl2 with inhibition of approximately 62% and 52% occurred with 8mM of EDTA and HgCl2 respectively, but stimulated by Ca2+ and Potassium ion K+. Activated carbon partially purified alpha amylase produced by A. niger with a high yield. The cations and chemicals had varying effects on the enzyme.
Characteristics of wind turbulence near the boundary layer in Three-North Regions of China
Authors: Li Yan , Guo Haiping , Li Lei
Published: October 2019

Based on the daily 10-minute wind observation data of the wind tower in CWERPON from 2013 to 2017, this study analysed the distribution and variation characteristics of wind turbulence in different gradients and periods in wind resource rich regions in NEC, NC and NWC. Results showed that: 1) The average wind speed from ground to 100 m height was 6.7m/s, which increased with the height, and the dominant wind speed was 4.0 m/s. The average wind speed at the height of 10 m, 30 m, 50 m, 70 m and 100 m were 6.0 m/s, 6.4 m/s, 6.7 m/s, 7.0 m/s and 7.5 m/s respectively. The highest and the lowest wind speed frequency occurred at the heights of 10m and 100m layers, which accounted for more than 22.5 % and 12.5 %. Starting from the wind speed of 6.0 m/s, the proportion of lower layers wind speed decreased, while that of high layers wind speed increased. 2) The average
It

decreased from low layers to high layers. Each layer’s
It

decreased gradually with the increasing of wind speed. The
It

values were different among these three regions in the study area, the NEC region was the largest, followed by the NWC, and the
It

value in NC stations were the smallest. Under the wind speed of 3.0-25 m/s and 15.0 m/s, the average
It

of each layer were 0.118 and 0.099 respectively; the maximum values were 0.189 and 0.120 at the height of 10 m in NEC region, and the minimum were 0.082 and 0.063, both of which appeared in the 100 m gradient in NC region and NWC region respectively. 3) The variation ranges of
It

among adjacent layers were different, the lower the layer was, the greater range of change occurred. The differences between the 10-30 m, 30-50 m, 50-70 m were 0.028, 0.013 and 0.003 respectively. 4) Each layer’s
It

corresponded to the variation trend of the air temperature.
It

increased slowly from 06:00, which reached the maximum value around 14:00, and then decreased slowly. 5) The wind turbine reach the C and B turbulence intensity level respectively at the height of 30 m and 10 m in the study area when the average wind speed is lower than 6.0 m/s, and some stations’ wind turbine type in these three regions should be at least A level.
An empirical model to predict glacier area changes in China
Authors: Tian Hongzhen , Yang Taibao , Liu Qinping
Published: October 2019

Prediction of glacier changes is crucial for our society to adapt to the ongoing climate change. First, using correlation analysis, we found that a climate index (annual temperature) is significantly correlated with glacier area changes in China. A linear empirical model was then constructed to predict glacier area changes using temperature projections from the Intergovernmental Panel on Climate Change (IPCC). By using a subset of the glacier area change data as training data and the rest as verification data, we confirmed that the ability of the model to predict is reliable. The model requires only simple inputs and is easy to use. It gives a means of obtaining information on glacier area changes in the future for people in other disciplines as well as glaciologists who only need general information concerning glacier area changes in China.
Correlation analysis of sewage removal rate and microbial quantity in plateau environment
Authors: Hao Kaiyue , Zong Yongchen , Li Yuanwei , Huang Decai , Duan Xiaolong
Published: October 2019

Based on A2O process in plateau environment, the correlation between the removal rate of chemical oxygen demand (COD), the total phosphorous (TP), total nitrogen (TN) and ammoniacal nitrogen (NH4
+-N) in anaerobic tank, anoxic tank and aerobic tank and the quantity of indicator microorganisms was analyzed with temperature, dissolved oxygen (DO) and the hydraulic retention time (HRT) as working conditions, and the curve regression model of water removal rule and the optimal working conditions were obtained through SPSS analysis. The results showed that the removal rates of COD, TN, TP and NH4
+-N were positively and negatively correlated with some indicator microorganisms. The three sets of curve regression models passed the significance test. The DO and COD were cubic models, HRT and COD were quadratic models, HRT and NH4
+-N were S curve models. When DO is 2∼3 mg/L, the removal rate of COD can reach 87%. When HRT is 30∼40 h, the removal rate of COD can reach more than 90%, and the removal rate of NH4
+-N can reach more than 50%.
Numerical simulation on the outdoor thermal comfort in view of urban renewal: A case study of Changsha, China
Authors: Chen Yaping , Zheng Bohong , Tian Fangzhou
Published: October 2019

Urban Renewal plays an important role in urban economic development and urban construction in China. A large number of cities are currently developing towards high-rise and high-density models which will affect microclimate. Firstly, it analysed the impact on urban wind and thermal environment during the removal and reconstruction of residential buildings using ENVI-met. Secondly, the correlation between wind and the thermal environment with building arrangement, building density, building height and green ratio in 7 ideal cases were studied. Thirdly, the Physiologically Equivalent Temperature (PET) index was simulated by RayMan to assess thermal sensation. Finally, a case study of Changsha was simulated, where a factory was reconstructed to residential buildings. The results showed that 1) The redeveloped site will affect the neighbour outdoor thermal comfort within the range of 100m, and the impact will be insignificant beyond 100m. 2) During the daytime, higher building height and building density can result in 0.05°C-0.13°C lower PET value. 3) Green space is more effective than the residential area in cooling at night during the summer.
Application of optical-fiber sensing to concrete support and continuous wall strain monitoring
Authors: Qi Junqiang , Wang Baojun , Wang Xing , Song Zhanpu , Cui Zhendong
Published: October 2019

Optical-fiber sensing technologies are being theoretically and practically researched. These technologies, possessing linear and real-time properties, realize the sectional analysis of strain and temperature and improve point monitoring methods in deep foundation pit supporting systems. In this paper, a field experimental model of the deep foundation pit supporting system was designed in the subway station in Suzhou, China, which utilizes optical-fiber sensing technology. In this field experiment, conventional monitoring methods, namely steel-bar meters, inclinometer, and water-level observation hole were firstly employed for comparative study. Distributed optical-fiber sensors (DOFS) were employed at the same time based on Brillouin optical time-domain analysis (BOTDA). The experimental results show that the DOFS can more comprehensively monitor the pit support system than the conventional methods. The fiber sensors data reflect the positive and negative strain distribution of the walls in a linear section and detect a leakage by analyzing abnormal data. The fiber sensors data response a linear increase of the axial strain with excavation depth, and a bending phenomenon is discovered by the data curves because of the excavation depth difference of the testing support. With temperature compensation, the fiber monitoring data are more accurate to the excavation result than the steel-bar does. Thus, the sensors can get a combined action function of steel-bar which used for testing axial force and temperature, inclinometer which used for testing wall horizontal displacement, and water-level observation holes with accurately monitoring data.
Characteristics and simulation study of ground fissure activities in Gaoliying, Beijing
Authors: Meng Zhenjiang , Fan Zhongjie , Fan Wendong , Qiao Jianwei , Leng Yanqiu , Wang Feiyong , Zhao Junyan
Published: October 2019

The ground fissures in Gaoliying, Beijing, has caused panic among local people, and also caused severe damage to buildings and public facilities in its affected area. This paper takes the ground fissures as the research prototype and reveals its development and activities characteristics by field investigation and trenching exploration; The Flac3D finite difference method has also been used to simulate and calculate the deformation and failure characteristics of model strata under different fault dislocations and varying descend amounts of groundwater level. The results show that the ground fissure in Gaoliying are linearly distributed and cause the destruction mainly by vertical dislocation and horizontal tension in the shallow strata; Moreover, the differential settlement of the upper and lower strata of the model near the fault increases with the increase of fault dislocation. Vertical displacement and stress of soils on both sides of the fault are quite different, and the difference increases with the decrease of groundwater level.
Clssification of flow standards of carbonate formation in Bereketli-Pirgui gas field
Authors: Xing Yuzhong , Guo Chunqiu , Cheng Muwei , Chen Pengyu , Shi Haidong , Yang Huiting
Published: October 2019

Callovian-Oxfordian carbonate formation in Bereketli-Pirgui gas field as an example was selected. This paper describes three methods for quantitative division of flow standards based on parameters such as pore throat size, FZI’s(Flow Zone Index), storage capacity, and flow capacity. In this connection, the results can not only reflect the meter-scale heterogeneity of reservoirs around wellbore, but also meet the requirements of the minimum number of flow standards in reservoir numerical simulations.

Based on the measured data of core porosity and core permeability of Callovian-Oxfordian formation, rock types are firstly identified, then the main flow standards are determined according to the FZI, and finally the main hydraulic flow standards are divided in the stratigraphic framework according to the storage capacity and flow capacity. In comparison with the single factor flow standard classification method, this method can not only realize the classification of flow standards of different scales, but also help to compare different flow standards with each other in the sequence of stratigraphic framework.

The result indicates that Callovian-Oxfordian formation has 5 main rock types (i.e. micritic limestones, bioclastic microcrystalline limestones, sparry bioclastic limestones and algal limestones), 8 different flow standards (i.e. FU1-FU8) and 4 hydraulic flow standards (i.e., flow channel, storage-flow unit, storage unit and barrier unit). The classification results with different methods have a good agreement.
Study on the formation characteristic of microbubbles used in sewage treatment
Authors: Sun Lixia , Fan Mingxu , Xu Bo , Yu Huadong , Wang Yue , Zhang Yufeng , Li Peng
Published: October 2019

Microbubble usually has very small volume, and it is difficult to rise in the water, so it can be used to wrap ozone for sewage treatment. In the present study, the experiments of bubble formation in a mechanical microfluidic device are developed. The effect of liquid flow rate and gas pressure on bubble formation characteristic was obtained through experiments. By observing experimental phenomena, it can be concluded that bubble growth process can be divided into three stages, and the law of the detachment volume and formation frequency of microbubbles under single variable factor was investigated by the control variable method. The investigation of bubble formation characteristic can help to control bubble detachment volume and formation frequency precisely.
Preparation of Hawaii nut shell biochar/graphene sponge and study on uranium adsorption properties
Authors: Yu Shoufu , Wu Xiaoyan , He Peng , Liu Yong , Shi Keyou , Zhang Qiucai , Zhang Xiaowen , Li Mi , Lv Chunxue
Published: October 2019

The composite sponge of Hawaii nut shell biochar and graphene oxide was prepared by using polyvinyl alcohol as three-dimensional composite carrier (BC/GO/PVA). The characterization analysis found that the composite sponge material has a good specific surface area of pore structure, and improved the plasticity of biochar, overcoming the stacking problem of graphene sheets, and proposed a reasonable material cross-linking composite mechanism. The optimum adsorption capacity and adsorption mechanism were analyzed by batch adsorption experiments. The results showed that the removal of uranium by BC/GO/PVA materials was beneficial under weakly acidic conditions. The maximum adsorption capacity of the experiment is 14.3 mg/g.
Analysis of Thermochemical Nonequilibrium Ablation Flow for a Hypersonic Hemispherical Nose
Authors: Shao Chun , Chen Yingchun , Zhang Miao , Shu Jun
Published: October 2019

The thermal protection materials enveloping hypersonic vehicles ablate. This paper develops a numerical methodology of thermochemical nonequilibrium flow and structure temperature field to study the key flow and structure parameters of a hypersonic hemispherical nose under the condition of carbon-based thermal protection material ablation. The multi-species chemical reaction model of flow field and the corresponding numerical algorithm are constructed. Oxidation and sublimation ablation process are considered in ablation model coupled with flow field solver by gas-solid interaction method. The computational results of a hemispherical nose indicate that carbon-based thermal protection material ablation has significant effects on thermochemical nonequilibrium flow. Details of the ablation flow characteristics are reported to highlight the influences of ablation on microcosmic reaction species and macroscopic flow parameters including shock wave position, pressure and temperature.
Design of an End-effector for Spacecraft Automatic Assembly Robot
Authors: Zhang Bin , Zhang Chengli , Xie Fugui , Yi Wangmin , Meng Shaohua , Wang Wei
Published: October 2019

With the increasing of large-weight equipment on spacecraft, the traditional assembly method using hoisting manual guidance has some shortcomings, such as poor flexibility, high risk of bumping, low assembly efficiency, etc. [1]. In recent years, robot assembly system has been widely used in spacecraft assembly process. End-effector is an important part of automatic assembly robot. In this paper, an end-effector for batch equipment installation with fast connection and fast release function was designed. Through simulation analysis and experimental verification, it proves that the end-effector has good performance and can meet the application requirements. It helps to raise efficiency and reduce cost for spacecraft assembly.
Research on Intelligent Grasping System of Monocular Vision Guided Manipulator
Authors: Jiabu Han , Saixuan Chen , Guohua Cui , Zhenyi Cheng , Shipei Li
Published: October 2019

In order to solve the problem of how a cooperative robot can quickly and accurately locate and grasp the specified target work piece and avoid obstacles autonomously under the condition of man-machine cooperation and the variable position of the object to be grasped, a new method of robot arm grasping under the visual guidance of ROS system was proposed. Using ROS framework and tools, the color threshold algorithm in ROS-Opencv is used to realize the rapid recognition and positioning of grasping targets. Use the ROS-Moveit! The kinematics calculation, motion planning and obstacle avoidance of the manipulator are completed the relationship between the image coordinate system and the robot coordinate system is established by hand eye calibration technology. In addition, ROS tools can be used to obtain information such as the position and speed of each joint during the movement of the mechanical arm. Through experimental testing and data analysis, it is shown that the hand-eye system is accurate in calibration, object positioning, and the robot arm can accurately grasp the target object, which has certain practical application value.