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Records with Subject: Other
Showing records 1 to 25 of 67. [First] Page: 1 2 3 Last
Investigation of Fracturing Network Propagation in Random Naturally Fractured and Laminated Block Experiments
Yu Wang, Xiao Li, Jianming He, Zhiheng Zhao, Bo Zheng
January 7, 2019 (v1)
Subject: Other
Keywords: fracture network propagation, hydraulic fracturing, laboratory test, random natural fractures, silty laminae
Researchers have recently realized thatsilty laminas are very developed in naturally fractured continentalsedimentary formations in the Ordos Basin(China). Studies have shown that silty laminas are significant to improve the physical properties and gas storage capacity, and the natural fractures interact with the hydraulic fractures to maximize the fracture network during hydraulic fracturing. However, the influence of silty laminas withrandom fractures on the created hydraulic fracture networkis not well understood. Laboratory experiments are proposed to investigate the evolution of fracture networks in naturally fractured formations with model blocks that contain laminas and random fractures. The influence of dominating factors was studied and analyzed, with an emphasis on stress ratio, injection rate, and laminae strength. Macroscopic failure morphology descriptions combined with meso 3-D laser scanning techniques are both used to reveal the evolution of fracture networks. It is sug... [more]
Analytical Investigation of the Magnetic-Field Distribution in an Axial Magnetic-Field-Modulated Brushless Double-Rotor Machine
Chengde Tong, Zhiyi Song, Jingang Bai, Jiaqi Liu, Ping Zheng
January 7, 2019 (v1)
Subject: Other
Keywords: analytical solution, axial flux, electromagnetic performance, magnetic field, magnetic-field-modulated brushless double-rotor machine (MFM-BDRM)
The axial magnetic-field-modulated brushless double-rotor machine (MFM-BDRM) is a novel possible alternative power-split device for hybrid electric vehicles (HEVs). This paper proposes a two-dimensional (2-D) analytical method to predict the performance of the axial MFM-BDRM to reduce computing time. The computation is based on the solution of Laplace’s or Poisson’s equation with boundary conditions for each elementary rectangular region. By taking account of the existence of modulating ring and the stator slotting effect, the proposed model is able to calculate magnetic-field distribution with high accuracy. In order to assess the proposed method, the 2-D analytical and three-dimensional (3-D) finite element analysis (FEA) results have been compared, and good agreements have been achieved. As the analytical computation is much faster and more flexible, the proposed method can be used in the preliminary design process of the axial MFM-BDRM.
Analytical Calculation of D- and Q-axis Inductance for Interior Permanent Magnet Motors Based on Winding Function Theory
Peixin Liang, Yulong Pei, Feng Chai, Kui Zhao
January 7, 2019 (v1)
Subject: Other
Keywords: armature reaction magnetic field, d- and q-axis inductances, interior permanent magnet motor, lumped parameter magnetic circuit model, nonlinearity, saturation, winding function theory
Interior permanent magnet (IPM) motors are widely used in electric vehicles (EVs), benefiting from the excellent advantages of a more rational use of energy. For further improvement of energy utilization, this paper presents an analytical method of d- and q-axis inductance calculation for IPM motors with V-shaped rotor in no-load condition. A lumped parameter magnetic circuit model (LPMCM) is adopted to investigate the saturation and nonlinearity of the bridge. Taking into account the influence of magnetic field distribution on inductance, the winding function theory (WFT) is employed to accurately calculate the armature reaction airgap magnetic field and d- and q-axis inductances. The validity of the analytical technique is verified by the finite element method (FEM).
Analysis and Performance Improvement of WPT Systems in the Environment of Single Non-Ferromagnetic Metal Plates
Linlin Tan, Jiacheng Li, Chen Chen, Changxin Yan, Jinpeng Guo, Xueliang Huang
January 7, 2019 (v1)
Subject: Other
Keywords: ferrite cores, impedance model, metal, resonator, wireless power transfer
Wireless power transfer (WPT) is greatly affected when the transmission channel is surrounded by non-ferromagnetic metallic objects and the alternating magnetic field interacts with the metal conductor, which is more of an issue in wirelessly charged electric vehicle (EV) applications. This paper analyses the performances of a WPT system in an environment with a non-ferromagnetic metal plate. The impedance model of the WPT system in the metal environment is established. Moreover the variation law of a coil’s equivalent inductance and resistance is deduced when the coil is surrounded by the non-ferromagnetic metal plate. Meanwhile, simulations, theory and experiments all confirm that the model is correct. Finally, since the system performance of a wireless charging system is influenced by non-ferromagnetic metals, this paper puts forward a method to improve the performance, that is, to place ferrite cores between the receiving coil and a metal plate. Experiments are carried out to verif... [more]
A Laboratory Study of the Effects of Interbeds on Hydraulic Fracture Propagation in Shale Formation
Zhiheng Zhao, Xiao Li, Yu Wang, Bo Zheng, Bo Zhang
January 7, 2019 (v1)
Subject: Other
Keywords: failure mechanism, fracture propagation, hydraulic fracturing, interbeds
To investigate how the characteristics of interbeds affect hydraulic fracture propagation in the continental shale formation, a series of 300 mm × 300 mm × 300 mm concrete blocks with varying interbeds, based on outcrop observation and core measurement of Chang 7-2 shale formation, were prepared to conduct the hydraulic fracturing experiments. The results reveal that the breakdown pressure increases with the rise of thickness and strength of interbeds under the same in-situ field stress and injection rate. In addition, for the model blocks with thick and high strength interbeds, the hydraulic fracture has difficulty crossing the interbeds and is prone to divert along the bedding faces, and the fracturing effectiveness is not good. However, for the model blocks with thin and low strength interbeds, more long branches are generated along the main fracture, which is beneficial to the formation of the fracture network. What is more, combining the macroscopic descriptions with microscopic o... [more]
Artist Photovoltaic Modules
Shui-Yang Lien
January 7, 2019 (v1)
Subject: Other
Keywords: building-integrated photovoltaic (BIPV), full-color, laser process, photovoltaic (PV) module
In this paper, a full-color photovoltaic (PV) module, called the artist PV module, is developed by laser processes. A full-color image source is printed on the back of a protective glass using an inkjet printer, and a brightened grayscale mask is used to precisely define regions on the module where colors need to be revealed. Artist PV modules with 1.1 × 1.4 m² area have high a retaining power output of 139 W and an aesthetic appearance making them more competitive than other building-integrated photovoltaic (BIPV) products. Furthermore, the installation of artist PV modules as curtain walls without metal frames is also demonstrated. This type of installation offers an aesthetic advantage by introducing supporting fittings, originating from the field of glass technology. Hence, this paper is expected to elevate BIPV modules to an art form and generate research interests in developing more functional PV modules.
Implementation of Rapid Prototyping Tools for Power Loss and Cost Minimization of DC-DC Converters
Amruta V. Kulkarni, Weiqiang Chen, Ali M. Bazzi
January 7, 2019 (v1)
Subject: Other
Keywords: DC-DC converters, design methodology, design optimization, rapid prototyping, user centered design, user interface
In this paper, power loss and cost models of power electronic converters based on converter ratings and datasheet information are presented. These models aid in creating rapid prototypes which facilitate the component selection process. Through rapid prototyping, users can estimate power loss and cost which are essential in design decisions. The proposed approach treats main power electronic components of a converter as building blocks that can be arranged to obtain multiple topologies to facilitate rapid prototyping. In order to get system-level power loss and cost models, two processes are implemented. The first process automatically provides minimum power loss or cost estimates and identifies components for specific applications and ratings; the second process estimates power losses and costs of each component of interest as well as the whole system. Two examples are used to illustrate the proposed approaches—boost and buck converters in continuous conduction mode. Achieved cost and... [more]
Experimental Study of Crack Initiation and Extension Induced by Hydraulic Fracturing in a Tree-Type Borehole Array
Yiyu Lu, Shaojie Zuo, Zhaolong Ge, Songqiang Xiao, Yugang Cheng
January 7, 2019 (v1)
Subject: Other
Keywords: acoustic emission, coal bed methane, coal permeability, hydraulic fracturing, tree-type borehole array
High-pressure hydraulic fracturing technology in coal and coal bed methane mines can lead to roof and floor damage, and fracture initiation disorder that leads to a “blank area”, and other issues. A new method of hydraulic fracturing is proposed to increase the homogeneous permeability of coal in underground coalmines. Numerical and other simulation tests for different forms of a tree-type, branched borehole model are presented. The results show that the branched array causes cracks to initiate from the bottom of the array, and these extend along the direction of the adjacent boreholes. Generally, as the number of branched boreholes increases, the coal seam fracture network also increase, improving the distribution of the fracture network, making the fracturing effect better. The branched boreholes appear to reduce initiation pressure and, with increasing branches, the initiation pressure decreases. A model with four tree-type, branched boreholes leads to a reduction in initiation pres... [more]
An Integrated Multifunctional Bidirectional AC/DC and DC/DC Converter for Electric Vehicles Applications
Liwen Pan, Chengning Zhang
January 7, 2019 (v1)
Subject: Other
Keywords: AC/DC converter, DC/DC converter, electric vehicle, integrated bidirectional charger
This paper presents an on-board vehicular battery charger that integrates bidirectional AC/DC converter and DC/DC converter to achieve high power density for application in electric vehicles (EVs). The integrated charger is able to transfer electrical energy between the battery pack and the electric traction system and to function as an AC/DC battery charger. The integrated charger topology is presented and the design of passive components is discussed. The control schemes are developed for motor drive system and battery-charging system with a power pulsation reduction circuit. Simulation results in MATLAB/Simulink and experiments on a 30-kW motor drive and 3.3-kW AC/DC charging prototype validate the performance of the proposed technology. In addition, power losses, efficiency comparison and thermal stress for the integrated charger are illustrated. The results of the analyses show the validity of the advanced integrated charger for electric vehicles.
A Study on a Linear Magnetic-Geared Interior Permanent Magnet Generator for Direct-Drive Wave Energy Conversion
Ningjun Feng, Haitao Yu, Minqiang Hu, Chunyuan Liu, Lei Huang, Zhenchuan Shi
December 3, 2018 (v1)
Subject: Other
Keywords: finite element analysis, linear permanent magnet generator, magnetic gear, wave energy conversion
The conventional linear permanent magnet generator (CLPMG) for direct-drive wave energy conversion (WEC) has experienced many drawbacks that are difficult to overcome such as low power density and bulky system volume. To improve power density, this paper proposes a linear magnetic-geared interior permanent magnet generator (LMGIPMG) with tubular topology, which artfully incorporates a linear magnetic gear into a linear permanent magnet generator. The operating principle of the LMGIPMG is introduced, and a detailed analysis of air gap flux density, thrust force characteristics, and no-load and load performances are presented and discussed by using finite element method. The CLPMG, which produces the same power as the LMGIPMG, has about four times the volume of the latter. A prototype CLPMG is manufactured to verify simulation results against experimental tests. The design method and the operation conditions of LMGIPMG and CLPMG are both consistent; thus, the performance of LMGIPMG meets... [more]
Slide Valves for Single-Screw Expanders Working Under Varied Operating Conditions
Yuting Wu, Ruiping Zhi, Biao Lei, Wei Wang, Jingfu Wang, Guoqiang Li, Huan Wang, Chongfang Ma
December 3, 2018 (v1)
Subject: Other
Keywords: organic Rankine cycle (ORC), part-load, single-screw expander, slide valve
This paper fully describes the working principle of slide valves in single-screw expanders (SSEs). A geometric analysis of suction and volume ratio slide valves is presented to determine the relations between volume ratio, suction closure volume, discharge opening volume and slide valves displacement. An organic Rankine cycle (ORC) thermodynamic model with SSE integrated with slide valves is developed to analyze the power output of SSE and the net power output of ORC system and variation law of slide valves displacement. Analysis of a typical ORC system under changing operating conditions shows that the power output of the expander and the net output power of the ORC system with slide valves are much better than those without slide valves. When the condensing temperature is 40 °C and the waste availability is 80 kW, the increase in output power and net output power are approximately 3.4 kW and 5 kW, respectively. The presented geometric analysis of slide valves and the thermodynamic mo... [more]
A Novel Design of Radio Frequency Energy Relays on Power Transmission Lines
Jin Tong, Yigang He, Bing Li, Fangming Deng, Tao Wang
November 28, 2018 (v1)
Subject: Other
Keywords: high-voltage power transmission line, radio frequency identification (RFID) technology, wireless energy transmission
In this paper, we investigate the energy problem of monitoring sensors on high-voltage power transmission lines and propose a wireless charging scheme for a Radio Frequency IDentification (RFID) sensor tag to solve a commercial efficiency problem: the maintenance-caused power outage. Considering the environmental influences on power transmission lines, a self-powered wireless energy relay is designed to meet the energy requirement of the passive RFID sensor tag. The relay can obtain the electric field energy from the transmission lines and wirelessly power the RFID sensor tags around for longer operating distance. A prototype of the energy relay is built and tested on a 110 kv line. The measurement results show that the energy relay can provide stable energy even with the influences of wind, noise and power outage. To our knowledge, it is the first work to power the RFID sensor tags on power transmission lines.
Streamer Propagation and Breakdown in a Very Small Point-Insulating Plate Gap in Mineral Oil and Ester Liquids at Positive Lightning Impulse Voltage
Pawel Rozga
November 28, 2018 (v1)
Subject: Other
Keywords: breakdown, lightning impulse, mineral oil, natural ester, streamer propagation, synthetic ester
This article presents the results of comparative studies on streamer propagation and breakdown in a point-insulating plate electrode system in mineral oil and two ester liquids. The studies were performed for a 10-mm gap and a positive standard lightning impulse. The work was focused on the comparison of light waveforms registered using the photomultiplier technique. The results indicated that both esters demonstrate a lower resistance against the appearance of fast energetic streamers than mineral oil. The reason for such a conclusion is that the number of lightning impulses supplied to the electrode system for which the above-mentioned fast streamers appeared at a given voltage level was always higher in the case of ester liquids than mineral oil. In terms of breakdown, the esters tested were assessed as more susceptible to the appearance of breakdown in the investigated electrode system. The number of breakdowns recorded in the case of esters was always greater than the correspondin... [more]
A Novel Protection Method for Single Line-to-Ground Faults in Ungrounded Low-Inertia Microgrids
Liuming Jing, Dae-Hee Son, Sang-Hee Kang, Soon-Ryul Nam
November 28, 2018 (v1)
Subject: Other
Keywords: distributed energy resources, microgrid protection, single line-to-ground (SLG) fault, ungrounded low-inertia microgrid
This paper proposes a novel protection method for single line-to-ground (SLG) faults in ungrounded low-inertia microgrids. The proposed method includes microgrid interface protection and unit protection. The microgrid interface protection is based on the difference between the zero-sequence voltage angle and the zero-sequence current angle at the microgrid interconnection transformer for fast selection of the faulty feeder. The microgrid unit protection is based on a comparison of the three zero-sequence current phase directions at each junction point of load or distributed energy resources. Methods are also included to locate the minimum fault section. The fault section location technology operates according to the coordination of microgrid unit protection. The proposed method responds to SLG faults that may occur in both the grid and the microgrid. Simulations of an ungrounded low-inertia microgrid with a relay model were carried out using Power System Computer Aided Design (PSCAD)/E... [more]
Combining Unsteady Blade Pressure Measurements and a Free-Wake Vortex Model to Investigate the Cycle-to-Cycle Variations in Wind Turbine Aerodynamic Blade Loads in Yaw
Moutaz Elgammi, Tonio Sant
November 28, 2018 (v1)
Subject: Other
Keywords: dynamic stall, free-wake vortex model, NREL Phase VI rotor, unsteady angle of attack, wind turbine aerodynamics, yawed rotor
Prediction of the unsteady aerodynamic flow phenomenon on wind turbines is challenging and still subject to considerable uncertainty. Under yawed rotor conditions, the wind turbine blades are subjected to unsteady flow conditions as a result of the blade advancing and retreating effect and the development of a skewed vortical wake created downstream of the rotor plane. Blade surface pressure measurements conducted on the NREL Phase VI rotor in yawed conditions have shown that dynamic stall causes the wind turbine blades to experience significant cycle-to-cycle variations in aerodynamic loading. These effects were observed even though the rotor was subjected to a fixed speed and a uniform and steady wind flow. This phenomenon is not normally predicted by existing dynamic stall models integrated in wind turbine design codes. This paper couples blade pressure measurements from the NREL Phase VI rotor to a free-wake vortex model to derive the angle of attack time series at the different bl... [more]
Prospects of Biodiesel Production from Macadamia Oil as an Alternative Fuel for Diesel Engines
Md Mofijur Rahman, Mohammad Rasul, Nur Md Sayeed Hassan, Justin Hyde
November 28, 2018 (v1)
Subject: Other
Keywords: alternative fuel, blending, emission, macadamia oil, properties
This paper investigated the prospects of biodiesel production from macadamia oil as an alternative fuel for diesel engine. The biodiesel was produced using conventional transesterification process using the base catalyst (KOH). A multi-cylinder diesel engine was used to evaluate the performance and emission of 5% (B5) and 20% (B20) macadamia biodiesel fuel at different engine speeds and full load condition. It was found that the characteristics of biodiesel are within the limit of specified standards American Society for Testing and Materials (ASTM D6751) and comparable to diesel fuel. This study also found that the blending of macadamia biodiesel⁻diesel fuel significantly improves the fuel properties including viscosity, density (D), heating value and oxidation stability (OS). Engine performance results indicated that macadamia biodiesel fuel sample reduces brake power (BP) and increases brake-specific fuel consumption (BSFC) while emission results indicated that it reduces the averag... [more]
Application of a Diffuser Structure to Vertical-Axis Wind Turbines
Koichi Watanabe, Shuhei Takahashi, Yuji Ohya
November 28, 2018 (v1)
Subject: Other
Keywords: vertical-axis wind turbine, wind acceleration device, wind lens, wind tunnel experiment
The effects of using a wind acceleration device (wind lens) with vertical-axis wind turbines in wind tunnel experiments were examined. A wind lens consists of a diffuser and flanges, and this study investigated the optimum parameters of their configuration with regard to the power augmentation of the turbines. The wind lens with a flat-panel-type diffuser demonstrated power augmentation by a factor of 2.0 compared with an open wind turbine. An increase from 5° to 20° in the semi-open angle of the diffuser made it possible to generate a 30% high power output over a wide range of tip speed ratios. On that basis, an optimum semi-open angle was determined. For the flat-panel-type diffuser, a recommended diffuser length is the half of the throat width, and its semi-open angle is 20°.The inlet enhanced power augmentation over a wide range of tip speed ratios. The optimum location for the wind lens in the streamwise direction was aligned with the center of the vertical-axis wind turbines. The... [more]
Experimental Study of Natural Convection Cooling of Vertical Cylinders with Inclined Plate Fins
Jong Bum Lee, Hyun Jung Kim, Dong-Kwon Kim
November 28, 2018 (v1)
Subject: Other
Keywords: inclined plate fin, natural convection, nusselt number
In this paper, natural convection from vertical cylinders with inclined plate fins is investigated experimentally for use in cooling electronic equipment. Extensive experimental investigations are performed for various inclination angles, fin numbers, and base temperatures. From the experimental data, a correlation for estimating the Nusselt number is proposed. The correlation is applicable when the Rayleigh number, inclination angle, and fin number are in the ranges 100,000⁻600,000, 30°⁻90°, and 9⁻36, respectively. Using the correlation, a contour map depicting the thermal resistance as a function of the fin number and fin thickness is presented. Finally, the optimal thermal resistances of cylinders with inclined plate fins and conventional radial plate fins are compared. It is found that that the optimal thermal resistance of the cylinder with inclined fins is 30% lower than that of the cylinder with radial plate fins.
Nanostructured p-Type Semiconductor Electrodes and Photoelectrochemistry of Their Reduction Processes
Matteo Bonomo, Danilo Dini
November 27, 2018 (v1)
Subject: Other
Keywords: CO2 reduction, dye-sensitized solar cell, metal chalcogenides, metal oxides, p-type, photoelectrochemistry, reduction, semiconductor, solar fuels
This review reports the properties of p-type semiconductors with nanostructured features employed as photocathodes in photoelectrochemical cells (PECs). Light absorption is crucial for the activation of the reduction processes occurring at the p-type electrode either in the pristine or in a modified/sensitized state. Beside thermodynamics, the kinetics of the electron transfer (ET) process from photocathode to a redox shuttle in the oxidized form are also crucial since the flow of electrons will take place correctly if the ET rate will overcome that one of recombination and trapping events which impede the charge separation produced by the absorption of light. Depending on the nature of the chromophore, i.e., if the semiconductor itself or the chemisorbed dye-sensitizer, different energy levels will be involved in the cathodic ET process. An analysis of the general properties and requirements of electrodic materials of p-type for being efficient photoelectrocatalysts of reduction proce... [more]
Effects of Different Factors on Electrical Equipment UV Corona Discharge Detection
Zhenyu Li, Licheng Li, Xingliang Jiang, Jianlin Hu, Zhijin Zhang, Wei Zhang
November 27, 2018 (v1)
Subject: Other
Keywords: corona discharge, correction, gain, observation angle, observation distance, photon number, UV imaging
As a non-contact discharge detection method, ultraviolet (UV) imaging can rapidly, directly, and securely detect corona discharges. Therefore, UV imaging has been widely applied to power systems. To study the influences of different factors on UV corona discharge detection, two typical types of UV imagers (DayCor®Superb and CoroCAM®6D) were utilized. Results show that the observation angle has little impact on UV detection if no obstacles block the detection line of sight. Given that different UV imagers have different optimal imager gains, photon numbers under different gains could be calibrated to the values under optimal gains in accordance with the gain correction formula. Photon numbers decrease with the increase in the square of observation distance. Detection results under different observation distances could be corrected to the contrast distance after the detection of electrical equipment. The photon numbers of different UV imager types could be corrected in accordance with th... [more]
Review of Physicochemical-Based Diagnostic Techniques for Assessing Insulation Condition in Aged Transformers
Janvier Sylvestre N’cho, Issouf Fofana, Yazid Hadjadj, Abderrahmane Beroual
November 27, 2018 (v1)
Subject: Other
Keywords: acidity, color/visual examination, DGA, diagnostics, dissolved decay products, DP, free radicals, FTIR spectroscopy, furan, gas chromatography-mass spectrometry coupling, HPLC, inhibitor content, insulating oil/paper, interfacial tension, Methanol, moisture, particle count, power transformers, turbidity, UV/visible spectroscopy, viscosity
A power transformer outage has a dramatic financial consequence not only for electric power systems utilities but also for interconnected customers. The service reliability of this important asset largely depends upon the condition of the oil-paper insulation. Therefore, by keeping the qualities of oil-paper insulation system in pristine condition, the maintenance planners can reduce the decline rate of internal faults. Accurate diagnostic methods for analyzing the condition of transformers are therefore essential. Currently, there are various electrical and physicochemical diagnostic techniques available for insulation condition monitoring of power transformers. This paper is aimed at the description, analysis and interpretation of modern physicochemical diagnostics techniques for assessing insulation condition in aged transformers. Since fields and laboratory experiences have shown that transformer oil contains about 70% of diagnostic information, the physicochemical analyses of oil... [more]
Development of Integrally Molded Bipolar Plates for All-Vanadium Redox Flow Batteries
Chih-Hsun Chang, Han-Wen Chou, Ning-Yih Hsu, Yong-Song Chen
November 27, 2018 (v1)
Subject: Other
Keywords: all-vanadium redox flow battery (VRBs), bipolar plate (BP), Energy Storage, injection molding
All-vanadium redox flow batteries (VRBs) are potential energy storage systems for renewable power sources because of their flexible design, deep discharge capacity, quick response time, and long cycle life. To minimize the energy loss due to the shunt current, in a traditional design, a flow field is machined on two electrically insulated frames with a graphite plate in between. A traditional bipolar plate (BP) of a VRB consists of many components, and thus, the assembly process is time consuming. In this study, an integrally molded BP is designed and fabricated to minimize the manufacturing cost. First, the effects of the mold design and injection parameters on frame formability were analyzed by simulation. Second, a new graphite plate design for integral molding was proposed, and finally, two integrally molded BPs were fabricated and compared. Results show that gate position significantly affects air traps and the maximum volume shrinkage occurs at the corners of a BP. The volume shr... [more]
Modeling for Three-Pole Radial Hybrid Magnetic Bearing Considering Edge Effect
Huangqiu Zhu, Shuling Ding, Jintao Jv
November 27, 2018 (v1)
Subject: Other
Keywords: edge effect, hybrid magnetic bearing (HMB), magnetic bearing, mathematical model, radial suspension force
In order to overcome the shortcoming of magnetic bearings whereby general mathematical models of the radial suspension forces cannot be accurately established, a mathematical model considering the edge effect is set up. The configuration, operation principle and flux distribution features of a three-pole radial hybrid magnetic bearing (HMB) are analyzed in this paper. The magnetic field division method is employed to calculate the permeance of different regions around the end portion of poles. The total permeance of a single pole is composed of the permeance of the regions. Then, an accurate mathematical model of the radial suspension forces considering the edge effect is deduced by the equivalent magnetic circuit method. From the modeling procedures, it can be seen that the edge effect calculation is only related to the configuration and parameters of the magnetic poles, and is isolated with the other configurations and parameters of the three-pole radial HMB, therefore, the mathemati... [more]
Evaluation of Batteries for Safe Air Transport
Nicholas Williard, Christopher Hendricks, Bhanu Sood, Jae Sik Chung, Michael Pecht
November 27, 2018 (v1)
Subject: Other
Keywords: aviation, Batteries, public safety, standards, transportation
Lithium-ion batteries are shipped worldwide with many limitations implemented to ensure safety and to prevent loss of cargo. Many of the transportation guidelines focus on new batteries; however, the shipment requirements for used or degraded batteries are less clear. Current international regulations regarding the air transport of lithium-ion batteries are critically reviewed. The pre-shipping tests are outlined and evaluated to assess their ability to fully mitigate risks during battery transport. In particular, the guidelines for shipping second-use batteries are considered. Because the electrochemical state of previously used batteries is inherently different from that of new batteries, additional considerations must be made to evaluate these types of cells. Additional tests are suggested that evaluate the risks of second-use batteries, which may or may not contain incipient faults.
Design and Analysis of Jacket Substructures for Offshore Wind Turbines
I-Wen Chen, Bao-Leng Wong, Yu-Hung Lin, Shiu-Wu Chau, Hsin-Haou Huang
November 27, 2018 (v1)
Subject: Other
Keywords: buckling analysis, jacket structure, offshore wind turbine, static analysis
This study focused on investigating various existing types of offshore jacket substructures along with a proposed twisted-tripod jacket type (modified jacket (MJ)-structures). The architectures of the three-leg structure, as well as the patented twisted jacket structure motivated the design of the proposed MJ-structures. The dimensions of the structures were designed iteratively using static stress analysis to ensure that all structures had a similar level of load-carrying capability. The numerical global buckling analyses were performed for all structures after the validation by the scaled-down experiments. The local buckling strength of all compressive members was analyzed using the NORSOK standard. The results showed that the proposed MJ-structures possess excellent structural behavior and few structural nodes and components competitive with the patented twisted jacket structures, while still maintaining the advantages of low material usage similar to the three-leg jacket structures... [more]
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