Maximum Charges Research Articles

An analytical study of blasting vibration using deep mining and drivage rules

For the study on the propagation–attenuation rule of the blasting vibration wave in the deep mining roadway of Shizishan copper mine, and the analysis of the influences of different maximum explosive charges and different underground systems on the propagation of blasting vibration signals, blasting vibration monitoring of the two different situations has been carried out respectively. Firstly, the Sadov’s Formula has been applied to analyzing the monitoring results of the mining roadway, and thus the value of its excavation blasting vibration attenuation index K and \(\alpha \) and its corresponding regression formula were attained; then, the appropriate regression formula was used to calculate the maximum explosive charge which could ensure the safety of the principal chambers underground the mine. Meanwhile, on the basis of the HHT analysis method, the rule of vibration wave propagation under these two different situations was analyzed. And the results indicated that, whether with an increase in the single charge, or with an increase in the number of the underground systems to cross, blasting seismic wave had a tendency for spreading to the low-frequency band. Through the regression analysis of the Sadov’s Formula and the HHT Method, the results provided a reliable basis for the safe and efficient production of the mine.

A Comparative Study of Ground and Underground Vibrations Induced by Bench Blasting

Ground vibrations originating from bench blasting may cause damage to slopes, structures, and underground workings in close proximity to an operating open-pit mine. It is important to monitor and predict ground vibration levels induced by blasting and to take measures to reduce their hazardous effects. The aims of this paper are to determine the weaker protection objects by comparatively studying bench blasting induced vibrations obtained at surface and in an underground tunnel in an open-pit mine and thus to seek vibration control methods to protect engineering objects at the site. Vibrations arising from measurement devices at surface and in an underground tunnel at the Zijinshan Open-Pit Mine were obtained. Comparative analysis of the peak particle velocities shows that, in the greatest majority of cases, surface values are higher than underground values for the same vibration distance. The transmission laws of surface and underground vibrations were established depending on the type of rock mass, the explosive charge, and the distance. Compared with the Chinese Safety Regulations for Blasting (GB6722-2014), the bench blasting induced vibrations would not currently cause damage to the underground tunnel. According to the maximum allowable peak particle velocities for different objects, the permitted maximum charges per delay are obtained to reduce damage to these objects at different distances.

Fabrication and characterization of curcumin-loaded albumin/gum arabic coacervate

In this study, gum arabic (GA) and bovine serum albumin (BSA) were used for encapsulation of poorly water-soluble curcumin (CN) by complex coacervation method. To optimize coacervate formulation, three factors including pH (3.7–4.2), BSA/GA weight ratio (3:1, 2:1, 1:1) and CN content (1000–5000 μg), at three levels were examined in central composite design (CCD) using response surface methodology (RSM). A quadratic polynomial equation was used for encapsulation efficiency (EE) optimization. The complex coacervation between GA and BSA was restricted to a narrow pH range, where both molecules carry maximum opposite charges. Optimum conditions were found at BSA/GA weight ratio of 2:1 and pH 3.7. Encapsulation efficiency in this condition was found to be around 92%. Scanning electron microscopy (SEM) revealed a sponge-like coacervate phase and showed the size in the range of 40–80 μm. Further characterization of dried coacervates was performed using XRD and DSC. Penetration test showed that among three mentioned variables, biopolymers ratio had a dominant effect on texture. This study showed that the BSA/GA emulsification-coacervation is an efficient and promising technique for CN encapsulation according to encapsulation efficiency and facility of the method.

Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a suitable passivation layer to suppress oxidation in metal oxide thin films for enhanced lifetime in inverted organic solar cells.

PSO를 이용한 물 재이용 펌프시스템의 에너지 비용 제어

This paper presents a control method for energy cost saving in the water reuse pumping system. An optimize horizon switching strategy is proposed to implement an pump control. And Particle Swarm Optimization (PSO) algorithm is used to solve optimal problems in each time step. Energy costs are calculated for electricity on both TOU in the light, heavy, and maximum load time period and peak charges. The control method in water reuse pumping systems is determined to reduce the TOU cost. The simulation results show a energy cost saving for water reuse pumping systems.

Experimental Study on Observation and Evaluation of Partial Discharges in an Embedded Artificial Cylindrical Cavity between Glass Epoxy Boards

For the purpose of supporting the understanding of partial discharge (PD) phenomena for student education in electrical engineering, an introduction of experimental proposal for practical training which includes experiment and theoretical calculation is taken into consideration. In succession of the technical education for diagnosis of insulation degradation, the knowledge about PD carried out an important role in the background of this consideration. The experimental sample which is laminating an insulated board with a cylindrical shape cavity between the common glass-reinforced epoxy laminate boards, which mostly used in printed circuit boards, was made for the evaluation of the internal PD phenomenon. In addition, the medium-layer board with the cavity was evaluated also to the case where it was considered as a PTFE board and a CFRP board. The content of this experiment is intended to make it understand the intensity of internal PD generated by impression of AC high voltage. The amount q of charges (the apparent amount of PD charges) in the cavity was observed first, and the amount qmax of the maximum charges was evaluated below as compared with a simple calculation model.

Entropy-product rules for charged rotating black holes

We study the universal nature of the product of the entropies of all horizons of charged rotating black holes. We argue, by examining further explicit examples, that when the maximum number of rotations and/or charges are turned on, the entropy product is expressed in terms of angular momentum and/or charges only, which are quantized. (In the case of gauged supergravities, the entropy product depends on the gauge-coupling constant also.) In two-derivative gravities, the notion of the "maximum number" of charges can be defined as being sufficiently many non-zero charges that the Reissner-Nordstrom black hole arises under an appropriate specialisation of the charges. (The definition can be relaxed somewhat in charged AdS black holes in $D\ge 6$.) In higher-derivative gravity, we use the charged rotating black hole in Weyl-Maxwell gravity as an example for which the entropy product is still quantized, but it is expressed in terms of the angular momentum only, with no dependence on the charge. This suggests that the notion of maximum charges in higher-derivative gravities requires further understanding.

Environmental response of pectin-stabilized whey protein aggregates

Electrostatically-stabilized complexes are highly sensitive to changes in their local environment. The current study investigated the formation and stability of particles by heating (90 °C, 5 min) whey protein isolate (WPI) and pectin together as affected by the degree of esterification (DE), whey protein (WP):Pectin ratio (8:1, 5:1, and 2:1), and pH (6–4). At pH 6.0, primary complex formation between WP and pectin was shown, whereas this effect was more pronounced for low-methoxyl pectin (LMP) than for high-methoxyl pectin (HMP) based systems. At pH 4.0, maximum opposite net charges on both biopolymers and maximum biopolymer interactions were observed. Heat-treated WP-Pectin mixtures tended to form more compact and stable structures than unheated ones, associated with the lower pH sensitivity of protein. LMP-stabilized WP systems were characterized by many small aggregates (∼15 μm), whereas HMP-stabilized WP systems exhibited large (∼50 μm) but very dense aggregated structures, which is associated with interpolymeric complexation. Since LMP-stabilized WP aggregates meet the size characteristics of milk fat globules, they might have potential to replace parts of fat in fermented milk products.

Helmeted vs Nonhelmeted

This article reports on a retrospective review of the outcomes from 2-wheeled vehicle accidents and the impact of helmet use or non-use. The authors focus on the state of Florida, which rescinded its mandatory motorcycle helmet law in 2000. In the 10 years since this change, helmet use has dropped dramatically, and motorcycle fatalities have increased rapidly. In this study, the authors analyzed all 2-wheeled vehicle accidents evaluated at a level 1 trauma center over a 5-year period (2005-2010), comparing all outcomes, costs, and insurance status for helmeted and nonhelmeted riders (n = 1,439). Outcomes were compared for baseline population statistics, Glasgow Outcome Scale score, cost of hospitalization, discharge outcome, and health insurance status. In the 1,331 patients with full data, 995 (74.8%) were involved in motorcycle accidents, 249 (18.7%) were involved in bicycle accidents, and 87 (6.5%) were involved in scooter/moped accidents. Overall, 749 riders were nonhelmeted and 582 were helmeted. In the motorcycle group, there were 522 helmeted and 473 nonhelmeted riders. For the population of bicycle riders, there were 204 male and 45 female riders. For all vehicle types, hospital charges were skewed to the right, with a few expensive stays raising the overall average. For motorcycle riders, the average and median charges were significantly higher in nonhelmeted patients. For bicycle and scooter patients, no statistical significance was found; however, overall maximum charges were greatest in the nonhelmeted patients. In regard to insurance status, overall, riders wearing helmets were significantly more likely to have insurance than nonhelmeted riders. The authors conclude that, for the largest population (motorcycle riders), the results clearly demonstrate that helmets are effective in decreasing mortalities and improving outcomes at discharge. Also, as expected from the mortality and outcomes data, helmets significantly reduce the hospital charges for motorcycle riders involved in accidents. In estimating the cost savings for motorcycle helmet use, the authors found an average cost savings per helmeted patient of $23,603. The authors conclude that the age and insurance exemption of the law should be revoked and a universal helmet law be reinstated in the state of Florida. Motorcycle helmets significantly reduce overall morbidity and mortality, improve discharge outcome, and are cost-effective in healthcare savings.

에너지절감을 위한 물 재이용 펌프시스템의 최적운전 제어

본 논문에서는 물 재이용 펌프 시스템의 에너지 효율적 운전 방법을 제안한다. 1시간 단위의 시간대에서 최적운전제어를 위해 예측구간 스위칭방법과 선형계획법을 적용하고 에너지 비용은 경부하, 중부하, 그리고 최대부하를 포함한 TOU 요금과 피크요금을 통해 산정하도록 한다. 물 재이용 펌프시스템에서의 최적운전은 TOU 요금과 피크요금을 포함한 에너지 비용을 최대로 줄일 수 있도록 수행한다. 시뮬레이션을 통해 제안한 최적운전방법을 적용하면 많은 전력 에너지 비용의 절감과 전력계통의 안정성 향상을 확인할 수 있다. This paper presents an optimal operation control method for energy saving in the water reuse pumping system. A predictive horizon switching strategy is proposed to implement an optimal operation control and a linear programming (LP) algorithm is used to solve optimal problems in each time step. Energy costs are calculated for electricity on both TOU in the light, heavy, and maximum load time period and peak charges. The optimal operation in water reuse pumping systems is determined to reduce the TOU and peak costs. The simulation results show a power energy saving for water reuse pumping systems and power stability improvement.

A model predictive control strategy for load shifting in a water pumping scheme with maximum demand charges

This paper defines and simulates a closed-loop optimal control strategy for load shifting in a plant that is charged for electricity on both time-of-use (TOU) and maximum demand (MD). A model predictive control approach is used to implement the closed-loop optimal control model, and the optimization problem is solved with integer programming. The simulated control model yields near optimal switching times which reduce the TOU and MD costs. The results show a saving of 5.8% for the overall plant, and the largest portion of the saving is due to a reduction in MD. The effect of disturbances, model uncertainty and plant failure is also simulated to demonstrate the benefits of a model predictive control model.

Quantum-chemical descriptors and the assessment of surface activity in coal flotation

The activity of reagents in coal flotation may be assessed on the basis of quantum-chemical descriptors. Semiempirical calculations indicate that hard electrophilic centers in the coal surface correspond to carbon atoms with maximum positive charge. The oxygen atoms are nucleophilic centers of complex terephthalates, which are characterized by maximum negative charges and therefore able to form donoracceptor complexes with electrophilic sections of the coal surface. The reaction corresponds to a charge-controlled mechanism.

Suppression of carbon buildup and lifetime improvement by heating carbon stripper foils

We have successfully developed a new method to reduce the amount of carbon buildup on thin cluster (less than 3.5 μg/cm 2) carbon stripper foils by heating them with infrared radiation during beam bombardment. We studied the carbon buildup and the foil temperature on foil lifetime using a 2.0 ± 0.5 μA beam of 3.2-MeV Ne + ions. It was found that the carbon buildup begins to rapidly suppress at 460 °C; further, at a foil temperature higher than approximately 820 °C, the initial foil thickness did not change until the foil ruptured. We also found that the carbon buildup shortens the lifetime of stripper foils. The foils treated by the newly developed present method could withstand the maximum and average total beam charges of 530 mC/cm 2 and 340 mC/cm 2, respectively, which are approximately 18 and 11 times larger than the values for the best commercially available foils and approximately 3 and 2 times greater than the values for the cluster foils that are not treated by this method.

Effects of Pressure, Temperature, and Gas Velocity on Electrostatics in Gas−Solid Fluidized Beds

The influences of operating pressure, temperature, and gas velocity on the degree of electrification in a fluidized bed of glass beads and different grades of polyethylene resin were investigated in a fluidization column of 150-mm inner diameter and 2.0-m height. Eight collision ball probes at different levels and radial positions measured the degree of electrification in the bed. Faraday cups also measured the charge density in the bed by taking samples from three different online sampling ports at different levels. The degree of electrification increased as pressure increased from 1.0 to 8.0 bar, probably due to an increase in bubble rise velocity, frequency, and volume fraction. The maximum static charges were found at approximately two-thirds of the bed height and near the axis. As the pressure increased, particle−particle and particle−wall collisions near the distributor and wall contributed heavily to static charge generation. At higher temperatures (up to 75 °C), the bed exhibited smoother fluidiza...

Heterocoagulation-spray drying process for the inclusion of ceramic pigments

The improvement of the physico-chemical resistance of hematite pigment in ceramic bodies has been pursued through its inclusion into a transparent and refractory matrix of silica or zirconia. The inclusion process was accomplished by heterocoagulation followed by spray-drying. The heterocoagulation process was optimised through an electrokinetic technique, that measured the ζ potential of both matrix and pigment as a function of pH and of different amounts of dispersing agents. Suspensions of pigment and matrix were designed in order to achieve the maximum surface charges. The heterocoagulated mix was then spray-dried in order to avoid any separated coagulation of pigment and matrix and to obtain a well granulated powder suitable for application in ceramic bodies. A stable red-coloured ceramic pigment for low firing applications was obtained starting from amorphous silica as matrix and hematite as colorant.

Otosclerosis: Mid-Term Results of Cochlear Implantation

Introduction: Constant histological changes in otosclerosis lead to progressive hearing loss which may end up in a profound hearing loss and then be treated by means of cochlear implants. These progressive changes could be followed by changes in cochlear implants fitting and speech discrimination results over the years. Objectives: The aim of the study is to correlate the progressive histological changes to the cochlear implant clinical outcomes (fitting and speech discrimination results). Also main complications (facial nerve stimulation and difficulties at insertion) and new complications will be discussed. Design: A 5-year prospective case-control study was performed in order to compare cochlear implant results in otosclerosis patients to those in a matched-pair control group. Materials and Methods: Fifteen otosclerosis patients were followed throughout the study. Preoperatively temporal bone high-resolution computed tomography, electrically evoked auditory brainstem responses and speech discrimination tests were performed in order to select the patients to be implanted. Results: Not only difficulties with electrode guide insertion were reported, but also difficulties with fitting over the years, due to increasing difficulties to spread the electrical stimuli, which provokes increasing thresholds, maximum comfort levels and charges needed to stimulate hearing cells in basal and medial turn electrodes (p < 0.05), which required deactivating some basal and medial turn electrodes in order to improve cochlear implant effectiveness. The results demonstrated no statistical differences in speech discrimination in otosclerosis patients compared to the control group (p > 0.05). Several complications were reported: facial nerve stimulation (7.14%) and sudden episodes of tinnitus and headaches (14.28%). Conclusions: Although progressive histological changes in otosclerosis lead to increasing thresholds, maximum comfort levels and charges needed to stimulate hearing cells, speech discrimination results support the cochlear implantation in otosclerosis.

Control of nanoparticle charge via condensation magnification

Previously, we reported a method for preparing highly charged nanoparticles via condensation magnification [Suh, J., Han, B., Kim, D. S., & Choi, M. (2005). A method for enhanced charging of nanoparticles via condensation magnification. Journal of Aerosol Science, 36, 1183–1193]. In the present work, we attempt to control the charge level of nanoparticles by varying the droplet size in the condensation magnification method. We also investigate whether both metallic and dielectric nanoparticles could be highly charged and their charge level can be controlled. Three different cases of 12 and 25 nm gold particles and 22 nm polystyrene polymer (PSP) particles were examined and for all three cases, the number of elementary charges could be successfully controlled by varying droplet sizes. The maximum charges of 12 and 25 nm gold nanoparticles were about 15 and 57 units, respectively, and that of 22 nm polystyrene polymer (PSP) particles was 43 units. Surface electric field strength corresponding to these maximum charges was found to be approximately independent of particle sizes indicating that ion evaporation model could be valid in our charging process.

Audiovisual materials in UK public libraries: economic sense?

PurposeThe purpose of this paper is to examine the provision of audiovisual materials in UK public libraries and their economic value.Design/methodology/approachA questionnaire survey of all the public library authorities in the UK was used to investigate current provision of audiovisual material, expected future provision, and the amounts spent on and generated by audiovisual collections. Data collected, together with those available from other reputable sources, were then used to estimate the cost benefit or value of audiovisual provision.FindingsThe provision of audiovisual material in UK public libraries is widespread and varied. While audiovisual collections provide economic value and generate income from charging for loans, there are significant costs inherent in providing such services. Concerns are raised about the constant developments in media formats and the ability to make adequate provision. A cost benefit of 1:1.34 using the PVB (present value benefits) based on maximum loan charges was found, meaning that the UK gets £1.34 direct benefit from every £1.00 spent on the audiovisual service.Research limitations/implicationsThere are different methods used by economists to estimate value of public services, all having limitations. The method used in this research is no exception. The cost‐benefit ratio found is based on maximum loan charges. However, this figure would be higher if the PVB had been based on purchase costs or lower if the PVB had been based on mean loan charges. Further, the figures do not include indirect benefits or option benefits, so are likely to be underestimates of the true cost benefit of the audiovisual service.Practical implicationsThis research is likely to be of interest to public library managers and funding bodies needing evidence for the value of audiovisual provision.Originality/valueThis is the first attempt to put a monetary value on audiovisual provision in the UK. It also provides insights into current and future audiovisual provision.

Formation of fast multicharged heavy ions under the action of a superintense femtosecond laser pulse on the cleaned surface of a target

It is found that the mean charge of tungsten ions in a solid tungsten target cleaned from the surface layer of hydrocarbon and oxide compounds and exposed to femtosecond laser radiation with an intensity exceeding 1016 W/cm2 attains 22+, while the maximum charge is 29+. The maximum energy of such ions approaches 1 MeV. The corresponding values obtained on a dirty target with the same laser pulse parameters constitute 3+, 5+, and 150 keV. The results of numerical simulation show that such a large maximum charge of ions can be attained owing to the emergence of an electrostatic ambipolar field at the sharp boundary between the plasma and vacuum. The main mechanism of ionization of ions with maximum charges is apparently impact ionization in the presence of an external quasi-static field. In addition, direct above-threshold ionization by this field can also play a significant role. It is also shown that heavy ions in a clean target are accelerated by hot electrons. This leads to the formation of high-energy ions. The effect of recombination on the charge of the ions being detected is analyzed in detail.

Low Hydrogen Content Silicon Nitride Films Deposited at Room Temperature with an ECR Plasma Source

Silicon nitride layers with very low hydrogen content (less than 1 atomic percent) were deposited at near room temperature, from and with a multipolar electron cyclotron resonance plasma. The influences of pressure and nitrogen flow rate on physical and electrical properties were studied in order to minimize the hydrogen and oxygen content in the layers. The optimized layers were characterized by a refractive index of 1.98, a dielectric constant of 7.2, and Si/N ratio values of 0.78. The layers exhibited very good dielectric strength, which was confirmed by large breakdown fields of 12 MV/cm, very high resistivities of Ω cm, and maximum charges to breakdown values of 90 C/cm2. Increasing the deposition pressure and decreasing the flow improved the SiN/Si interface, due to increased oxygen incorporation. The dominant conduction mechanism in the layers was the Poole-Frenkel effect. The critical field and the trap energy had similar dependencies on deposition pressure. Fowler-Nordheim tunneling occurred at high gate biases, for the layers deposited at the highest pressure of about 22 mTorr. © 2004 The Electrochemical Society. All rights reserved.