bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Nano-Scale Pore Size Distribution on Fluid Phase Behavior of Gas IOR in Shale Reservoirs
Authors: Luo Sheng , Lutkenhaus Jodie L. , Nasrabadi Hadi
Published: March 2018

The improved oil recovery of unconventional shale reservoirs has attracted much interest in recent years. Gas injection, such as CO2 and natural gas, is one of the most considered techniques for its sweep efficiency and effectiveness in low permeability reservoirs. However, the uncertainties of fluid phase behavior in shale reservoirs pose a great challenge in evaluating the performance of gas injection operation. Shale reservoirs are featured with macro-scale to nano-scale pore size distribution in the porous space. In fractures and macropores, the fluid shows bulk behavior, but in nanopores the phase behavior is significantly altered by the confinement effect. The integrated behavior of reservoir fluids in this complex environment remains uncertain.

In this study, we investigate the nano-scale pore size distribution effect on the phase behavior of reservoir fluids in gas injection for shale reservoirs using a multi-scale equation of state modeling. A case of Anadarko Basin shale oil is used. The pore size distribution is discretized as a multi-scale system with pores of specific diameters. The phase equilibria of methane injection into the multi-scale system are calculated. The constant composition expansions are simulated for oil mixed with various fractions of injected gas. Bubble point, swelling factor, criticality and fluid volumetrics are studied in comparison to the behavior of the bulk fluid. It is found that fluid in nanopores becomes supercritical with injected gas, but lowering the pressure below bubble point will turn it into the subcritical state. The swelling factor is slightly higher with nanopores, and bubble point is lower than the bulk. The degree of deviation depends on the amount of injected gas.
A Systematic Study of the Effect of Plugging on Polymer Flooding in W Offshore Oilfield of Bohai Bay
Authors: Li Baozhen , Kang Xiaodong , Zhang Jian , Tang Engao , Wei Zhijie , Yu Wei
Published: March 2018

Polymer flooding, as the most effective chemical EOR technique, was widely and used in onshore oilfields in the world. Also, it has been successfully applied in China offshore oilfields as a major EOR technology. In general, compared with water flooding, the production rate in polymer flooding drops by less than 30% according to observations of onshore field application. However, the production rate dropped much more severely in mid to late stage of polymer flooding for plugging problems in W offshore oilfield, which is over 50% in some producers and leads to poor flooding performance and less incremental oil. In this study, we perform a systematic analysis through integrating production dynamic analysis, well testing and reservoir simulation for the mechanisms and impacts of the plugging during the polymer flooding based on actual field data. First, a typical 1-injector & 1 producer polymer flooding reservoir model was established. Through simulation with the detailed description of reservoir and polymer properties, the impacts of key parameters affecting the production rate of producers in different stages of polymer flooding were analyzed. In addition, the dynamic characteristics of well performance under the condition of different plugging location were examined. After that, the local grid radial refinement technology was utilized to calculate the plugging degree and pollution radius of the target wells. Finally, a full-field corner grid system numerical model with local grid radial refinement near the wellbore was built in W fileld. We performed history matching with target injectors and producers and determined the plugging degree of pollution radius near above wells.

Through this field case study, the relationship between production rates and different stages of polymer flooding was identified. In addition, a diagnostic plot for characterizing the impact of plugging location on dynamic well performance was generated. Furthermore, the degree of plugging and pollution radius of all target wells was determined accurately. This study provides critical insights for understanding the polymer plugging mechanism and its effect on polymer flooding effectiveness in the offshore oil field. It also delivers a good reference for plugging removal design and optimization of polymer flooding strategy to maximize oil recovery.
Viscous Fingering in Reservoirs With Long Aspect Ratios
Authors: Hamid S. A. , Muggeridge A.
Published: March 2018

This paper investigates the impact of aspect ratio on the growth rate of viscous fingers using high resolution numerical simulation in reservoirs with aspect ratios of up to 30:1. The behaviour of fingers in porous media with such high aspect ratios has been overlooked previously in many previous simulation studies due to limited computational power.

Viscous fingering is likely to adversely affect the sweep obtained from any miscible gas injection project. It can also occur during polymer flooding when using chase water following the injection of a polymer slug. It depends upon the viscosity ratio, physical diffusion and dispersion, the geometry of the system and the permeability heterogeneity. It occurs because the interface between a lower viscosity displacing fluid and a higher viscosity displaced fluid is intrinsically unstable. This means that any small perturbation to the interface will cause fingers to grow. It is therefore almost impossible to predict the exact fingering pattern in any given displacement although many previous researchers have shown that it is possible predict average behaviour (such as gas breakthrough time and oil recovery) provided a very refined grid is used such that physical diffusion dominates over numerical diffusion. It is impossible to use such fine grids in field scale simulations. Instead engineers will tend to use standard empirical models such as the Todd and Longstaff or Koval models, calibrated to detailed simulations, to estimate field scale performance.

At late times in high aspect ratio systems, we find that one finger dominates the displacement and that this finger grows with the square root of time, rather than linearly. We also observe that this single finger tends to split, during which time the solvent oil interface length grows linearly with time before one finger again dominates and grows with the square root of time. This cycle can repeat several times. We also find that industry standard empirical models cannot properly capture the average behavior of the fingering in these cases because they assume linear growth as a function of time. We show that a modified Peclet number can be used to estimate when these empirical models are no longer valid.
Pilot Scale CO2 EOR at Wellington Filed in South Central Kansas
Authors: Holubnyak Yevhen , Watney Willard , Hollenbach Jennifer , Rush Jason , Fazelalavi Mina , Bidgoli Tandis , Wreath Dana
Published: March 2018

Baseline geologic characterization, geologic model development, studies of oil composition and properties, miscibility pressure estimations, geochemical characterization, reservoir modelling were performed. In March of 2015 the injection well (class II) KGS 2-32 was drilled, cored, and logged through an entire anticipated injection interval. Whole core samples were obtained and tested for porosity and permeability, relative permeability, and capillary pressure. The Drill Stem Test (DST) was also conducted to estimate injection interval permeability and pore-pressure. After the injection well KGS 2-32 was acidized, Step Rate (SRT) and Interference (IT) tests were conducted and analysed for permeability, well pattern communication, and fracture closing pressure.

Approximately 20,000 metric tons of CO2 was injected in the upper part of the Mississippian reservoir to verify CO2 EOR viability in carbonate reservoirs and evaluate a potential of transitioning to geologic CO2 storage through EOR. Total of 1,101 truckloads, 19,803 metric tons, average of 120 tonnes per day were delivered over the course of injection that lasted from January 9 to June 21, 2016. After cessation of CO2 injection, KGS 2-32 well was converted to water injector and is currently continues to operate. CO2 EOR progression in the field was monitored weekly with fluid level, temperature, and production recording, and formation fluid composition sampling.

As a result of CO2 injection observed incremental average oil production increase is ~68% with only ~18% of injected CO2 produced back. Simple but robust monitoring technologies proved to be very efficient in detection and locating of CO2. High CO2 reservoir retentions with low yields within actively producing field could help to estimate real-world risks of CO2 geological storage.

Wellington filed CO2 EOR was executed in a controlled environment with high efficiency. This case study proves that CO2 EOR could be successfully applied in Kansas carbonate reservoirs if CO2 sources and associated infrastructure is available.
Mechanistic Modeling of Carbonated Waterflooding
Authors: Sanaei Alireza , Varavei Abdoljalil , Sepehrnoori Kamy
Published: March 2018

CO2 enhanced oil recovery is usually affected by poor sweep efficiency due to unfavorable mobility contrast between the injected CO2 and oil. To alleviate this problem, CO2 is added to the injected brine and transported in the reservoir by flood water. Therefore, Carbonated Water Injection (CWI), takes advantage of both CO2 and water flooding processes. Furthermore, geochemical reactions between the injected carbonated brine and rock can alter petrophysical properties of the reservoir and affect final oil recovery. While there are several CWI coreflood experiments reported in the literature, simulation studies for this process are scarce.

Accurate modeling of CWI performance requires a simulator with the ability to capture true physics of the CWI process. In this study, a compositional reservoir simulator developed at The University of Texas at Austin, UTCOMP, coupled with a state-of-the-art geochemical package developed by United States Geological Survey, IPhreeqc, is used to model CWI process. We considered the impact of CO2 mass transfer between brine and hydrocarbon phases based on thermodynamic constrains at the reservoir condition. In order to validate our simulation approach, the results of our CWI simulations were compared with a recently published coreflood experiment. Moreover, we investigated the fluid-rock interactions in CWI.

The results of the simulations, indicated that prior to water breakthrough the main drive mechanism is displacement. But as more carbonated water is injected, CO2 diffuses more into the trapped oil left behind, which results in oil swelling and subsequent oil viscosity reduction. Moreover, reaction of carbonate minerals such as calcite with carbonated brine results in dissolution of the main rock matrix which consequently creates wormholes similar to carbonates acidizing.

In this study we propose a novel approach for accurate modeling of carbonated waterflooding process. The results of this study highlight the importance of geochemical reactions in modeling CWI process. Our approach has been validated based on history matching at the backdrop of a recently published coreflood experiment.
Simulations of In-Situ Upgrading Process: Interpretation of Laboratory Experiments and Study of Field-Scale Test
Authors: Perez-Perez A. , Mujica M. , Bogdanov I. , Brisset A. , Garnier O.
Published: March 2018

In-situ upgrading (IU) is a promising method of improved viscous and heavy oil recovery. The IU process implies a reservoir heating up and exposition to temperature higher than 300°C for long enough time to promote a series of chemical reactions. The pyrolysis reactions produce lighter oleic and gaseous components while a solid residue remains underground. In this work, we developed a numerical model of IU based on lab experiences (kinetics measurements and core experiments) and validated results applying our model to an IU test published it the literature. Finally, we studied different operational conditions searching for energy-efficient configurations.

In this work, two types of IU experimental data are used from two vertical-tube experiments with Canadian bitumen cores (0.15 m and 0.69 m). A general IU numerical model for the different experimental setups has been developed and compared to experimental data, using a commercial reservoir simulator framework. This model is capable to represent the phase distribution of pseudo-components, the thermal decomposition reactions of bitumen fractions and the generation of gases and residue (solid) under the cracking conditions.

Simulation results for the cores submitted to 370°C and production pressure of 15 bar, have shown that oil production (per pseudo-component) and oil sample quality were well-predicted by the model. Some differences in gas production and total solid residue were observed with respect to laboratory measurements. Computer-assisted history matching was performed using an uncertainty analysis tool on the base of the most important model parameters. In order to better understand IU field-scale test results, the Shell's Viking pilot (Peace River) was modeled and analyzed with proposed IU model. The appropriated grid-block size was determined and calculation time was reduced using the adaptive mesh refinement technique. The quality of products, the recovery efficiency and the energy expenses obtained with our model were in good agreement with the field test results. Also the conversion results (upgraded oil, gas and solid residue) from the experiments were compared to those obtained in the field test. Additional analysis was performed to identify energy efficient configurations and to understand the role of some key variables, e.g. heating period and rate, the production pressure, in the global IU upgrading performance. We discuss these results which illustrate and quantify the interplay between energy efficiency and productivity indicators.
Sociopragmatics of Code Switching and Code Mixing in Reconciliation Case Proceedings: Shariah Courts of Northern Nigeria
Authors: Ado Mohammed Ahmad , Bidin Siti Jamilah
Published: March 2018

Due to the peculiarity of the spoken language identified among parties involved in Reconciliation Case Proceedings (RCP) and their arbitrators in the Shariah Reconciliation courts, this paper explores some sociopragmatic aspects of the Hausa natives (Northern Nigeria, West Africa) Shariah reconciliation Courts judicial discourse. To this end, 12 various case proceedings of family disputes on marital issues were recorded through audiovisual recordings. The data were coded and analysed using Nvivo 10, focusing, amongst others, on Searle’s taxonomy of speech acts of expressiveness. It was found that Code Switching and Code Mixings (CSCM) appeared/employed constantly by almost all classes of speakers during RCP. The findings revealed that it is a sociopragmatic culture, behaviour and attribute of Hausa speakers of using Hausa switched, lexical mixed of Hausa-English or Hausa-Arabic CSCM expressive utterances in RCP. Arabic Terminologies and Hausanised of Arabic lexical are also employed by speakers in order to affirm, assert reciprocity, show respect, express gratitude or intention, offer defence, minimise imposition, and seek confirmation or explanation as well as Generic or honorific names/titles in RCP. Finally, the paper demonstrates that it is a cultural practice that during RCP, Hausa language is dominantly used as a medium of communication, hence, sometimes due to the Arabic and Islamic cultural influence of Hausa natives as well as being English as an official language in the Nigerian settings, CSCM of both the three languages is found to be part of the common feature of RCP within Bauchi state Shariah Commission of Nigeria.
Literature and Creativity in an ELT Context
Authors: Zaker Alireza
Published: March 2018

There is now a growing consensus among scientists and researchers that the mental and personal factors of individuals play a vital role in learning, especially learning English as a second language. Creativity, as one of these human factors, is believed to significantly affect L2 learning and life skills among human beings. Moreover, employing literature as the content of instruction in ELT is believed to provide EFL teachers and learners with numerous advantages, including higher levels of creativity. Based on this premise, this study suggests seven techniques which intend to promote creativity through employing literature in an EFL classroom. Following these techniques, some implementation concerns are stated in order to increase the chance of obtaining satisfactory results when employing these techniques. These concerns address the peculiarities of classroom environment, the role of cultural awareness, the importance of interaction, the significance of selecting a literary work, the appropriate feedback types, and motivation. The article concludes with some avenues for future research.
Morphological Description of Noun Formation Process: Case of Suffixation and Prefixation in Iguta Language
Authors: Ado Mohammed Ahmad , Bidin Siti Jamila
Published: March 2018

This paper dwells on a concise morphological description of Noun formation process involved in Iguta language (a minority endangered language in the north central, Nigeria). To this end, the paper explores the suffixation and prefixation processes involved in the formation of nouns of Iguta language. Ado’s (2017) 455 Iguta wordlists was employed as secondary data and was qualitatively used as instrument for the analyses in this paper. Ado’s 455 Iguta wordlists is primarily based on the standard dialect (i.e., Andirgiza) spoken by its native speakers in five selected towns in Jos North local government of the Plateau state, Nigeria. Hand analysis strategy and a thematic analytical process were used in developing insights on the language data during the analysis. The findings revealed ‘-char, -di and –e’ morphs as suffixes to inflect while  ‘t-, ti-, ha-, a-, an-, m-, i-, ma-, si-, ndu-, s-, tu-, tun-, tumu- morphs as  prefixes to either inflect or derive nouns. It is also observed that most singular nouns in Iguta are inflected to produce the plural forms using ti- or tu- prefixes especially when the pattern of the singular words begin with a vowel morpheme or phoneme. In accordance with the findings, it is suggested that prefixes and suffixes are part of the affixation process used in noun formation of Iguta language. In conclusion, the study has contributed in descriptive linguistics in terms inflectional or derivational suffixation and prefixation process used to build nouns in Iguta language. This paper may assist professional teachers and linguists in understanding the suffixations and prefixations existing in Iguta language.
Dual-role Conflict among Female Primary School Teachers
Authors: Faragai Lawal Abdul
Published: March 2018

This paper is a conceptual approach that stimulate able scholars that failed to ponder carefully on dual-role conflict among female primary school teachers. Of course, female primary school teachers are experiencing dual-role conflict. Also, presently female primary school teachers has dominated our primary schools teaching our children, on the same vain experiencing dual-role conflict which needed urgent attention from all stakeholders. The essence of this paper was due to the relevance of work and family matters. Scholars are really trying their best for enlightening all stakeholders on the issue of work-family role conflict in many discipline. In Education, related researches are always carrying on but the background level of education primary school is somehow been put aside with little concern. Considering this will help in making the work-life balance of female primary school teachers more sustainable. With this teaching and learning of our younger children would be efficient and effective. The researcher has proposed a conceptual framework in studying dual-role conflict among female primary school teachers. However, the qualitative interpretivist approach using case study or grounded theory would be applicable in conducting such type of research respectively.
First Language Interference and Form Focused Instruction
Authors: Fayyaz Shafaq , Swanto Suyansah , Din Wardatul Akmam
Published: March 2018

This paper addresses EFL/ESL teachers’ beliefs and practices regarding the use of the first language in a language classroom pertaining to the Form-Focused Instruction - a grammar instruction approach. In essence, this study looks into whether the judicious use of L1 in learning the foreign or second language is effective or not. A case study strategy was deemed appropriate for this study to explore and investigate the beliefs and practices of the non-native teachers on the use of L1 in learning English as a foreign language. To this end, six English language teachers were selected from a Chinese secondary school. The data were collected through classroom observations and stimulated recall interview questions. The audio-recorded data were fully transcribed in English, and subjected to a process of interpretative analysis. The findings revealed that teachers used L1 mainly to present the target grammar topics, to explain the grammatical rules and also to encourage students for the explanation of the grammatical rules in there L1. It is therefore imperative to consider the results of this study as it may highlight some notable pedagogical implications regarding the assisted effects of the use of first language on foreign/second language learning. 
Indonesian EFL Learners’ Perceptions of Classroom Learning Environments in An EFL Context
Authors: Arigusman Anggi
Published: March 2018

A good learning environment will determine the students’ learning quality. Therefore, creating supporting classroom learning environment is really crucial. This study explored the students’ perceptions at an Indonesian senior high school of actual classroom learning environment in English teaching across gender and grade. What Is Happening In this Classroom (WIHIC) questionnaire was  applied  to see  the  participants’ perceptions of the language learning environment. As for data analysis procedure, the scores obtained from the questionnaire were analyzed and described qualitatively. The data was examined to see how how is the students perception of their actual classroom learning environment in EFL classes across grade and gender. The result demonstrated similar perception indicated by five of the seven categories of the WIHIC questionnaire among grades. Across gender, four of the seven categories also indicated similar perception between male and female students where the categories get positively dominant result.
Extrovert versus Introvert Students: What EFL Learning Strategy do They Use?
Authors: Noprianto Eko
Published: March 2018

Since Indonesian students come from different cultures, languages and personality traits as well, recognizing their personality traits and their language learning strategy choice might be effective to help teacher design an effective teaching strategies to achieve learning objectives. This study was intended to find out (1) what personality traits Indonesian senior high school students fell into, and (2) to investigate what language learning strategies introvert and extrovert students used highly frequently. The 58 participants aged from sixteen to eighteen years old who were from the third grade of senior high school and were all from science class were given eighteen statements of McCroskey’s introversion scale to categorize them into extrovert and introvert and were administered with 32 statements of English Language Learning Strategy Inventory or ELLSI to see their learning strategy. The data were analyzed by means of descriptive statistics in terms of mean frequencies and statistical differences. The finding revealed that majority of senior high school students majoring science study program fell into introvert with 89.6% (52 students). Besides, extrovert students used more language learning strategy highly frequently than introvert students with eight items compared to introvert students with only five items. Interestingly, both extrovert and introvert students share four strategy items in common. Although it is statistically not significant (ρ > 0.05), the finding also shows that extrovert students seemed to use affective strategy more than introverts who used memory strategy highly frequently.
An analytical model for determining the effect of damping on 3D natural frequency of reinforced walls
Authors: Darvishpour Alireza , Ghanbari Ali , Hosseini S. A. A. , Nekooei Masoud , Darvishpour Tayyebeh
Published: March 2018

Most of the proposed methods for obtaining the free vibration natural frequency of the retaining wall assume the behavior of the wall in the two-dimensional domain, and they are not able to express the three-dimensional behavior of these structures in a satisfying manner. Moreover, the effect of damping has not yet been considered in analytical study. In this paper, the plate theory and Galerkin method is employed to analyze the free vibration of a wall-reinforcement-soil system in the three dimensional domain and survey the effect of damping on the natural frequency of a retaining wall. So, the retaining wall is modeled as a clamped-free plate and the stiffness of the soil and reinforcements existing behind the wall are modeled as a set of springs and the damping effect of the system is modeled by a set of dampers located at the back of the Retaining wall and attached to it. The results of the proposed model are compared with both the results of the other researchers and the ones from finite element method (FEM). They are also compared with the results of a full-scale experiment and it shows a good agreement. The proposed method which uses the plate theory, also yields the free vibration natural frequencies of the wall’s extensional modes with an acceptable accuracy. Finally, the effect of tensile and compressive behaviors of the soil and the reinforcements on the fundamental frequency of a reinforced retaining wall is studied.
New study on interactional effects of grouting pressure on the displacement of nailing bond
Authors: Abbasi Maedeh Pouyan , Wu Wei , Ghanbari Ali , Lin Jia , Al Dianty Marelianda , Ghaffari Irdmoosa Kourosh , Shahraki Ghadimi Amir
Published: March 2018

The maximum displacement in a soil nail bond system considering the pull-out, overburden load and grouting pressure effects has been evaluated. The Pull-out tests were carried out in five sites that located in Tehran, Iran. Moreover, additional pull-out test data from South Korea is considered. The displacement of the nailing system due to gravity and pressure grouting has been measured. Based on achieved data, four practical relationships between bound strength and pull-out displacements are developed. The parameters overburden load, grouting pressure, borehole diameter, moisture content and soil’s strength parameters have been chosen as the major inputs for the relationships. The correlation coefficients of the linear relationship range have been achieved between 0.89 and 0.99. While by using the multi-layer neural network for estimating it has been illustrated approximately 0.95.
Research on method of vibration analysis of rubber tracked vehicle based on dynamic model
Authors: Zhang Jinzheng , Wang Qi , Jin Qichun
Published: March 2018

To understand the vibration characteristics of rubber track system in traveling, this research studied the small harvester installed with rubber track system and the dynamic model reflecting vibration characteristics of rubber track system on the ground was constructed. Comparing analysis results with measured experimental data obtained from vehicle test, it is proved that the dynamic model established by theoretical analysis can correctly and effectively predict actual movement condition and vibration characteristics of rubber track system, especially at low test vehicle speeds. The relative difference between measured data of vibration acceleration obtained from real vehicle tests and the theoretical value was in the range of –1.2 %-+18.2 %. The vibration prediction and analysis method of rubber tracked vehicle was discussed in this study, and important basic data were provided for the research of comfort evaluation of working posture and lightweight design of rubber tracked mechanism.
Novel bearing fault diagnosis model integrated with dual-tree complex wavelet transform, permutation entropy and optimized FCM
Authors: Ma Ping , Zhang Hongli , Fan Wenhui , Wang Cong
Published: March 2018

In order to enhance the capability of feature extraction and fault classification of bearings, this study proposes a feature extraction approach based on dual-tree complex wavelet transform (DTCWT) and permutation entropy (PE), using the fuzzy c means clustering (FCM) to identify fault types. The vibration signal of bearings can be decomposed into several wavelet components with DTCWT which can describe the local characteristics of vibration signals accurately. And the PE of each wavelet component, which can describe the complexity of a time series, is calculated to be regarded as the fault features. Then forming the standard clustering centers by the FCM, we defined a standard using the Hamming approach degree to evaluate the classification results in the FCM. In order to verify the effectiveness of the proposed approach, compared with two other typical signal analysis methods: ensemble empirical mode decomposition (EEMD) and variational mode decomposition (VMD), through extracting fault features, it required to identify the fault types and severities under variable operating conditions. The experimental results demonstrate that the proposed approach has a better accuracy and performance to diagnose a bearing fault under different fault severities and variable operating conditions. The proposed approach is suitable for a fault diagnosis due to its good ability to the feature extraction and fault classification.
Base-isolation design of single-tower cable-stayed bridges: a case study in meizoseismal area
Authors: Yan Bin , Xia Ye
Published: March 2018

The single-tower cable-stayed bridge is one of the most popular types of bridges. Seismic design for this type of bridge, however, is rather difficult. When subjected to longitudinal earthquakes, the tower stands as the weakest part of all the bridge components. To solve this problem, a base-isolation design was developed and adopted for a practical single-tower cable-stayed bridge. In this design, laminated elastomeric bearings (EB) and liquid viscous dampers (LVD) were installed to serve as a base-isolation layer inside the tower cap. Numerical analysis was then conducted to investigate the variations of dynamic characteristics and seismic responses between conventional designs and base-isolation designs. LVD were used on the top of the transition pier to optimize the seismic system of the bridge. It was found that: i) the seismic loads acting on the bridge component were reduced as the seismic displacements increased. This was the result of amplification of the bridge vibration period by the EB in the base-isolation layer; ii) the seismic displacements were restrained by the LVD in the base-isolation layer, but the seismic forces increased due to improper parameter values; and iii) the seismic response decreased further by the transition pier’s LVD.
A new elastomeric-sliding seismic isolation system
Authors: Mozaheb Seyed Alireza , Behnamfar Farhad
Published: March 2018

A new seismic isolation system is introduced in this study that utilizes a combination of confined rubber for vertical loading and sliding rings for energy absorption. In this new system, a central elastomeric core is contained between the steel sliding rings. In laboratory testing of the proposed system, it was shown that the steel rings maintained the required vertical stiffness of the system by controlling the lateral deformation of the rubber core. In the lateral motion, the steel rings dissipated energy by sliding on each other under a friction force limited by their small share of the gravity loads. The advantages of the proposed system as compared with the conventional laminated-rubber bearing include increased vertical stiffness and energy absorption capacity as well as ease of manufacturing at a lowered cost.
Intelligent modeling of double link flexible robotic manipulator using artificial neural network
Authors: Jamali A. , Mat Darus I. Z. , Mohd Samin P. P. , Tokhi M. O.
Published: March 2018

The paper investigates the application of the Artificial Neural Network (ANN) in modeling of double-link flexible robotic manipulator (DLFRM). The system was categorized under multi-input multi-output. In this research, the dynamic models of DLFRM were separated into single-input single-output in the modeling stage. Thus, the characteristics of DLFRM were defined separately in each model and the coupling effect was assumed to be minimized. There are four discrete SISO model of double link flexible manipulator were developed from torque input to the hub angle and from torque input to the end point accelerations of each link. An experimental work was established to collect the input-output data pairs and used in developing the system model. Since the system is highly nonlinear, NARX model was chosen as the model structure because of its simplicity. The nonlinear characteristic of the system was estimated using the ANN whereby multi-layer perceptron (MLP) and ELMAN neural network (ENN) structure were utilized. The implementation of the ANN and its’ effectiveness in developing the model of DLFRM was emphasized. The performance of the MLP was compared to ENN based on the validation of the mean-squared error (MSE) and correlation tests of the developed models. The results indicated that the identification of the DLFRM system using the MLP outperformed the ENN with lower mean squared prediction error and unbiased results for all the models. Thus, the MLP provides a good approximation of the DLFRM dynamic model compared to the ENN.
Monitoring of blast-induced ground vibration using WSN and prediction with an ANN approach of ACC dungri limestone mine, India
Authors: Ragam Prashanth , Nimaje D. S.
Published: March 2018

Blast-induced ground vibration (BIGV) is an undesirable environmental issue in and around mines. Usage of a high amount of explosive causes ground vibrations that are harmful to the nearby habitats and dwellings. In this paper, an attempt has been made to monitor the BIGV with low-cost wireless sensor network (WSN) and prediction of peak particle velocity (PPV) using an artificial neural network (ANN) technique at ACC Dungri limestone mine, Bargarh, Odisha, India. Eleven blasts PPV were recorded at different locations using wireless sensor network prototype system. The data has been transmitted by ZigBee (IEEE 802.15.4) protocol. The results are very promising and the recorded PPV varies from 0.191 mm/s to 8.60 mm/s. A three-layer, feed-forward back propagation neural network consists of 6 input parameters, 5 hidden neurons, and one output parameters were trained. Obtained results were compared based on correlation of determination (R2) and standard error between recorded and predicted values of PPV.
Transform-domain sparse representation based classification for machinery vibration signals
Authors: Fajun Yu , Fuling Fan , Shuanghong Wang , Fengxing Zhou
Published: March 2018

The working state of machinery can be reflected by vibration signals. Accurate classification of these vibration signals is helpful for the machinery fault diagnosis. A novel classification method for vibration signals, named Transform Domain Sparse Representation-based Classification (TDSRC), is proposed. The method achieves high classification accuracy by three steps. Firstly, time-domain vibration signals, including training samples and test samples, are transformed to another domain, e.g. frequency-domain, wavelet-domain etc. Then, the transform coefficients of the training samples are combined as a dictionary and the transform coefficients of the test samples are sparsely coded on the dictionary. Finally, the class label of the test samples is identified by their minimal reconstruction errors. Although the proposed method is very similar to the Sparse Representation-based Classification (SRC), experimental results illustrates its performance is far superior to SRC in the classification of vibration signals. These experiments include: frequency-domain classification of bearing vibration data from the Case Western Reserve University (CWRU) Bearing Data Center and wavelet-domain classification of six fault-types gearbox vibration data from our rotating machinery experimental platform.
Design and dynamic testing of a roller coaster running wheel with a passive vibration damping system
Authors: Gierlak Piotr , Szybicki Dariusz , Kurc Krzysztof , Burghardt Andrzej , Wydrzyński Dawid , Sitek Radosław , Goczał Marek
Published: March 2018

This paper presents a design, a numerical analysis, a build-up and dynamic testing of an engineered and fabricated wheel with a passive vibration damping system designed for a roller coaster system. Taking into account the limited amount of space for fixing a wheel to a roller-coaster, this study shows an approach in which a special wheel design and viscoelastic inserts are used to reduce vibrations. A wheel comprises a rim and hub separated by a viscoelastic material and simultaneously connected by using spring steel fasteners with contractions ensuring elasticity. The dynamic tests of the wheel with a passive vibration damping system were completed with an assessment of the vibration reduction ratio in comparison to conventional roller coaster wheel types currently operated at the amusement park Energylandia located in Zator, Poland. Laboratory test results show reduction of vibrations by 36 % in the low frequency range, by 63 % in the medium frequency range and by 45 % in the high frequency range.
Development of a finger like multi-joint articulated surgical retractor for use in endoscopic surgery
Authors: Yamamoto Ikuo , Kishikawa Keiko , Kondo Yoshihiro , Lawn Murray , Nagayasu Takeshi , Yamasaki Naoya , Matsumoto Keitaro
Published: March 2018

The authors have developed an articulated medical instrument which assists with the movement of and maintenance of the position of such as a lung during surgery to assist providing improved viewability and providing the necessary space required to work efficiently and effectively. Conventionally holding such as, a lung in a given position is achieved by arranging gauze in an appropriate configuration with the aid of a simple shaft like surgical instrument, however for various reasons the gauze requires constant replacement and rearrangement resulting in significant surgical inefficiency. By using an articulated mechanism that mimics the functionality of fingers, we have developed a surgical device that inherently provides greater mechanical stability and does not require the use of gauze, thus enabling more efficient surgery. The prototyping process was assisted with the use of 3D-CAD to simulate static and dynamic conditions and a 3D-printer to confirm the concept and then a working prototype was created. In order to validate the dynamic functionality of this surgical instrument, it was tested on a porcine lung which closely approximates human lungs by a clinical doctor of thoracic surgery. The result was that the developed prototype articulated mechanism was able to stably move and hold the lung in position during surgery thus confirming the dynamic efficacy of the mechanism.
Numerical analysis of underwater flow past columnar projectile with different cross-sections at high Reynolds numbers
Authors: Yang Yongliang , Liu Rongzhong , Guo Rui , Chen Liang , Song Pu , Hu Hongwei
Published: March 2018

Based on Detached Eddy Simulation (DES) technique, the flow around a columnar projectile with different cross-section shapes in the supercritical and extremely supercritical region is simulated by the Fluent. The cross-section of the projectile is regular polygon, which number of edges is 4, 6, 8, 10, 12, 24 and ∞, where ∞ means a circle. The vortex shedding pattern and flow field characteristics are analyzed at Reynolds number 2.5×105 to 2×107. Regarding circular cylinder projectile, when the flow velocity changes from 25 m/s to 200 m/s, the average drag coefficient decreases, and the St Number increases. Regarding regular polygon, when the number of edges for polygon changes from 4 to ∞ at flow velocity 50 m/s, the average drag coefficient decreases, and the St Number increases. The average lift coefficient is almost equal to zero and does not change with the flow velocity and the cross-section. The pressure coefficient Cp of 4-prism, 6-prism, 8-prism, 12-prism and 24-prism has multiple local minimum values at the polygon vertices of the cross section. According to the spectrum analysis, the vortex shedding frequency of 4-prism, 24-prism and cylindrical is single and fixed, so the projectile may cause resonance and deviates from a predetermined trajectory. But for the 6-prism and 8-prism and 12-prism, the cl and cd is multi-periodic vibration. So, considering the flow induced structural vibrations, drag, the power of shrapnel and manufacturing cost, the 8-prism are better choices for cluster warhead underwater in engineering design.
Thickness shear vibration of a ZnO film structure covered with magnetic fluid
Authors: Liu Jing , Li Xiangyang , Zhang Weipeng
Published: March 2018

This paper aims to reveal the effect of magnetic liquid on the resonant frequency shift and the output impedance. For this purpose, a thin film sensor was designed with a finite-thickness layer of magnetic fluid, and the thickness shear vibration of the film was analysed in details. The main findings are as follows. First, the relative resonance frequency is positively correlated with the intensity of magnetic field, and the viscosity coefficient, density and volume fraction of magnetic fluid. The effect of magnetic field on the shift of the relative resonant frequency depends on various parameters of magnetic liquid. With the increase of the volume fraction, density and viscosity coefficient, the resonant frequency plunges, but the output impedance peak grows in size. Therefore, the relative resonant frequency shift and the output impedance are sensitive to various parameters in the design. The research findings shed new light on the application of thin piezoelectric film in sensors.
On the equations of the analytical dynamics of the quasi-3D plate theory of I. N. Vekua type and some their solutions
Authors: Kuznetsova Ekaterina L. , Kuznetsova Elena L. , Rabinskiy Lev N. , Zhavoronok Sergey I.
Published: March 2018

The plate theory of Nth order is constructed on the background of the Lagrangian variational formalism of analytical dynamics of continuum systems and the dimensional reduction approach of I. N. Vekua – A. A. Amosov. The plate model is defined within the configuration space, the set of field variables, and the Lagrangian density. The field variables are determined by the coefficients of the biorthogonal expansion of the spatial displacement vector field with respect to the dimensionless normal coordinate. The dynamic equations are derived as Lagrange equations of the second kind of the two-dimensional continuum system. The dynamics of the plane elastic layer is considered as an example, the normal wave propagation is described on the basis of refined plate theories of various orders, and the convergence of approximate solutions to the exact solution of the three-dimensional elastodynamics problem is analyzed for different wavenumbers.
Artifacts in magnetic resonance imaging: how it can really affect diagnostic image quality and confuse clinical diagnosis?
Authors: Budrys Tomas , Veikutis Vincentas , Lukosevicius Saulius , Gleizniene Rymante , Monastyreckiene Egle , Kulakiene Ilona
Published: March 2018

Different kinds of artifacts can occur during a magnetic resonance imaging (MRI) scans due to hardware or software related problems, human physiologic phenomenon or physical restrictions. Some of them can seriously affecting diagnostic image quality, while others may simulate or be confused with different pathology. On another word artifact as an artificial feature appearing in an image that is not present in the original investigative object. It is important to recognize these artifacts according to a basic understanding of their origin, especially those mimicking pathology, as they can lead to incorrect diagnosis and cause serious after-effects on patient’s health and outcomes. We presented an overview of the most common MRI artifacts and methods to fix or rectify them. We also provide the original artifacts images and statistics from the Lithuanian University of Health Sciences Kaunas Clinical Hospital, Dept of Radiology, mainly obtained from image databases and some images from data base of other Lithuanian hospitals.
Some studies on mathematical modeling and dynamic stress analysis of a variable compression ratio diesel engine crankshaft
Authors: Satyanarayana K. , Mohan Rao P. V. J. , Niranjan Kumar I. N.
Published: March 2018

The objective of the present work is to investigate the induced stress and deformation of a crank shaft. For this purpose, Variable Compression Ratio (VCR) engine is tested at 16.5 compression ratio. Peak pressures were recorded at various crank angles. A Matlab code is generated for dynamic analysis. For structural analysis and factor of safety, a three dimensional model crank shaft was developed using solid works. Finite element analysis of AISI E4340 Forged steel and Aluminum alloy 7076-T6 materials are carried by using analysis software ANSYS. The obtained results are equivalent Von-Mises stress, total deformation and factor of safety at different crank angles for the two materials are analyzed. It is concluded that Aluminum alloy exhibits better results than forged steel.
Study on friction mechanism and performance of disc brakes for mining motor vehicle
Authors: Qin Yanan , Zhang Sen , Wei Xiuping
Published: March 2018

According to the convexity theory, the working principle of the disc brake of mining motor vehicle is analyzed. The dry friction force between brake disc and brake block is mainly composed of three mechanisms, such as meshing effect, adhesion effect and furrow effect. The Link NVH 3900 device is used to simulate the long downhill braking condition with bench test method, which can obtain friction performance with high credibility in different brake conditions. The average friction coefficient and friction stability coefficient are chosen as the evaluation parameter for friction performance judgment. Through the research results, it can be known that the average friction coefficient of the brake decreases linearly with brake pressure increases, the friction stability coefficient under different braking pressure showed numerically larger and smaller fluctuations. When the temperature of disc surface exceeds 200 °C, the resin lubricating film will be produced in the brake block, which will decrease the friction coefficient obviously. The actual braking torque does not increase linearly with the increase of braking pressure, especially when the brake speed is high, the friction coefficient will decrease obviously.