bluuebunny/crossref_metadata_2025 huggingface dataset:
A Probabilistic Approach to Tight Gas Economic Evaluation: The Future of Argentina
Authors: Cervantes-Bravo R. J. , Ñaupari-Barzol H. , Palacios-Chun N. , Jimenez-Nieves E. T. , Magnelli D. , Huerta-Quiñones V. A.
Published: May 2017

Tight gas reservoir has potential to provide a significant contribution to meet the global energy demand. However, they involve technical and economic challenges for the commercialization that need to be addressed with the multidisciplinary integration of Geoscience, Engineering and Economics. Unconventional resource plays and tight gas reservoir, are generally characterized by lower geologic risk but higher commercial risk. For that reason, a precise understanding of the potential range can lead to the commercial success; this weighs on the economic evaluation process.

We will focus on local tight gas plays that differ in several aspects, especially in terms of the stage of commercial growth. Due to the large number of uncertainties, deterministic economic modeling provided results with low confidence and was considered as merely a scoping indication of commercial potential. Deterministic and single-point solutions are unable to provide a real check for the input assumptions, which typically leads to overly optimistic results. A better solution still needs to be found.

This paper transmits the consistent and systematic process employed in the evaluation of several tight gas plays, all softwares (e.g. Crystal Ball) tested, the vital role of multidisciplinary participation, iterative modeling efforts and conclusions. Thus, the generation of percentiles (P10, P50, and P90) for the economic indicators: NPV, IRR and Payout, through a probabilistic model that takes three scenarios in each input (Capex, Opex, Gas Price and Reserves); can yield to a more precise and sensible in return calculations of investments on an outlook, with the associated risk from a commercial point of view.

This case study was developed on a sectorial block of the Lajas Formation of the Neuquen Basin, with six wells in production (vertical wells 2000 – 2500 m), a GOIS of 129.22 BCF and a current recover factor estimated in 19 %. An optimum number of infill wells will be proposed with the aim to improve the recover factor higher than 35 % with and an incentive price of Gas Plus fixed at 7.5 US$/MMBTU from the National Government. Thus, the learning curve would be reduced and become to an energy source that enable to fulfill the future energy demand to a medium term for Argentina 2020 year, since the development of Vaca Muerta Shale Gas will have a long-term contribution.

Positive results are expected, which will be increased with the addition of each infill well of 4.2 % (5.38 BCF) in the EUR with a yield of investment (NPV/Investment) of 39 %.
Landscape Transformation Associated to the Development of Camisea Project and the Effectiveness of the Off Shore in Land Approach
Authors: Leunda G. , Dias G. , Mendoza E. , Capello N.
Published: May 2017

Objectives/Scope

The research presented herein was accomplished under the framework of the Camisea Project Biodiversity Monitoring Program, with the objective of assessing changes in land use and vegetation cover in Blocks 88 and 56, operated by Pluspetrol Peru Corp. The rate of recovery post intervention was also measured and recorded along a significant period of time (+ 10 years).

Methods, Procedures, Process

The area surveyed comprised approximately 247,000 ha for which satellite images (Landsat, CBERS2 and Aster) were used with mapping scales of 1:100,000 and 1:50,000. For further detail, a second stage using high resolution images (Ikonos, Quickbird, Wordview2 and aerial photography) was also performed.

Results, Observations, Conclusions

The results show that after 12 years of continuous operation the total cleared area within both blocks ranges between 0.13 and 0.20 %, with a tendency of remaining steady around the latter. This fluctuation is related with a dynamic of clearing and subsequent restoration works associated with the construction of project facilities, along with natural recovery. The research has provided, as well, data related with recovery rates of cleared areas, which range between 14 and 16 % per year.

Another important outcome of the study shows the relationship between the effect of activities directly associated with the Camisea Project and those conducted by third parties (government infrastructure, other extractive projects and native communities). Measured within a 5 year period, the deforestation rate of the Camisea Project tends to remain steady and has affected a small portion of the area (as previously informed, less than 0.2 %), whereas the surface deprived of vegetation by third parties increased 34 % during the 2011-2016 period.

Novel/Additive Information

Above all, the research clearly demonstrates the positive effects of the "offshore in land" strategy adopted by Pluspetrol in the early stages of the project. This avoided right of way clearance and road construction, requiring all logistics to be performed either aerial or fluvial. This has prevented both, unnecessary deforestation and, most important, the opening of new accesses for settlers that would push the agricultural frontier to an area which still remains an almost pristine rain forest.
Reducing Fault Reactivation Risk on Deepwater Drilling
Authors: Frydman M. , Holzberg B. , Pastor J. A. , Salies J. B. , Pedroso C. A.
Published: May 2017

Drilling in deepwater presents risks associated to fault reactivation, what includes severe drilling fluid losses, connection of different reservoirs and, in the worst case, connection of the reservoir to the sea floor, causing oil and gas seeps. Recent accidents along the Brazilian coast showed that such phenomena are real and associated risks should be evaluated before any well planning.

This work presents a method to identify and quantify risks of fault reactivation while drilling. An upper limit on the safe drilling window is proposed to account for these risks. The method also includes tridimensional stress analysis, where maps, slices and cubes with reactivations pressures over the faults are determined, what can be used to reduce risks by changing well positioning, casing points and mud weight plan.

The proposed method is based on two main pillars. The full 3D geomechanical characterization of the area, which is done through the 3D-Mechanical Earth Model, a consistent way to determine the stresses around faults; and a proper criterion to determine the potential risk of fault reactivation during drilling. For this, a criterion of slip tendency analysis based on frictional constrains is adopted.

The method can be applied under two methodologies. The first one represents the general case, where enhanced fault and in situ stresses characterizations are required. Through this approach, each fault plane is analyzed and more precise values of fault reactivation pressure are obtained. The second one is a simplification of the first one, and considers that all media is potentially faulted, where each potential fault is critically orientated with respect to the far field stress. This approach is recommended for exploratory or semi-exploratory scenarios, where faults are not very well mapped and main stresses directions are unknown.

A case study for a planning phase of a drilling campaign on a deepwater field located in Santos Basin, Brazil is presented. Fault reactivation risks were identified and quantified through the proposed method. Safe mud weight windows were determined accounting for fault reactivation pressures, which was valuable during well planning. Recommendations for casing points and mud weight plans could be done including fault reactivation risks. Examples of risk mitigation by avoiding problematic zones and by re-positioning planned wells were presented. Results showed that the proposed method is an important tool to identify, quantify and reduce fault reactivation risks while planning any drilling campaign.
Poultry Litter Ash Reduces Phosphorus Losses during Greenhouse Production of Lantana camara L. ‘New Gold’
Authors: Wells Daniel E. , Beasley Jeffrey S. , Gaston Lewis A. , Bush Edward W. , Thiessen Maureen E.
Published: May 2017

Phosphorus (P) fertilizers with high water-solubility are often applied in excessive amounts to porous horticultural substrates to produce high-quality plants. As a result, high P losses during containerized plant production have presented an environmental challenge to responsible growers. Poultry litter ash (PLA), a byproduct of bioenergy production, contains P concentrations comparable to conventional P fertilizers but is characterized as having lower water-solubility. Therefore, a series of experiments were conducted to characterize effects of PLA on container-plant growth and P leaching. PLA was compared with superphosphate (SP), a highly water-soluble P source, in ratios of 0:100, 25:75, 50:50, 75:25, and 100:0 (SP:PLA) in the production of Lantana camara L. ‘New Gold’. In 2011, lantana fertilized with higher ratios of PLA exhibited slower growth with lower shoot and root biomasses compared with 100% SP-fertilized lantana. However, in 2012, differences in fertilizer treatments lessened, with 100% PLA-fertilized lantana exhibiting 14% less shoot biomass and no differences in root biomass compared with 100% SP-fertilized lantana. Measurement of shoot:root biomass, a common indicator of P deficiency, was not different between any P treatments in 2011 or 2012. This indicates root growth was most likely the driving factor in P-treatment effects on shoot biomass in each year of the experiment. During a postproduction field trial, no differences in growth or biomass were observed between lantana previously fertilized with P, regardless of source. However, application of PLA as the single P source reduced dissolved reactive P (DRP) concentrations in leachate >90% and total P (TP) mass losses 69% compared with 100% SP-fertilized lantana during container production, with P treatments reducing DRP and TP losses as PLA ratios increased. Therefore, the benefit of P-loss reduction during container production achieved through PLA application may warrant the acceptance of slightly smaller plants or extending production cycles.
Pineapple (Ananas comusus) Plant Material as Supplement for Maize Residue-based Oyster Mushroom Substrate and Reduction of Cadmium Soil Contamination
Authors: Hlerema Igenicious N. , Eiasu Bahlebi K. , Koch Susan H.
Published: May 2017

Pineapple (Ananas comusus) production generates hard currency and, as a labor-intensive industry, it creates jobs. The profitability of pineapple farming in South Africa faces several challenges, including low yield potential and cadmium (Cd) contamination of soils, which damaged the reputation of the industry. To increase the income of pineapple farmers, research was conducted to evaluate the utilization of pineapple crop residue for oyster mushroom (Pleurotus ostreatus) production and to establish the Cd levels in the mushrooms produced on Cd-contaminated pineapple crop residue. Treatments were maize residue (M), pineapple residue (P), and a mixture of maize and pineapple residues [at 1:1 ratio (on a dry weight basis), M + P]. Biological efficiencies of 90%, 77.6%, and 29% were recorded for the M + P, P, and M treatments, respectively. The P and M + P substrates significantly increased mushroom yield. Mushroom protein contents were 23.3%, 18.86%, and 18.81% (on a dry weight basis) in the M + P, P, and M treatments, respectively. Mushrooms in the P substrate had the highest Cd level (3.3 mg/kg). In the M + P substrate, Cd reduced to a safe level (0.15 mg/kg). This indicates that mushrooms have biosorption capacity, and could be used to solve the problem of Cd pollution and increase the income of pineapple production.
Camellia as an Oilseed Crop
Authors: Liang Haiying , Hao Bing-Qing , Chen Guo-Chen , Ye Hang , Ma Jinlin
Published: May 2017

Camellia is one of the four main oil-bearing trees along with olive, palm, and coconut in the world. Known as “Eastern Olive Oil,” camellia oil shares similar chemical composition with olive oil, with high amounts of oleic acid and linoleic acid and low saturated fats. Camellia was first exploited for edible oil in China more than 1000 years ago. Today, its oil serves as the main cooking oil in China’s southern provinces. Introduction of camellia oil into the Western countries was delayed until the recognition of its many health benefits. Although popularity for the oil has yet to grow outside of China, interest has emerged in commercial production of camellia oil in other countries in recent years. Unlike seed-oil plants that are grown on arable land, oil camellias normally grow on mountain slopes. This allows the new crop to take full usage of the marginal lands. To facilitate promoting this valuable crop as an alternative oil source and selecting promising cultivars for targeted habitats, this paper reviews the resources of oil camellias developed in China, use of by-products from oil-refining process, as well as the progress of developing camellias for oil production in China and other nations.
Increasing Survival of Splice-grafted Watermelon Seedlings Using a Sucrose Application
Authors: Dabirian Sahar , Miles Carol A.
Published: May 2017

Rootstock regrowth can prevent effective healing of grafted vegetable seedlings and outcompete the scion for light, space, and nutrients later in production. Rootstock regrowth is especially problematic for watermelon (Citrullus lanatus) because the crop is most commonly grafted using methods where meristematic tissue remains on the rootstock. The objective of this study was to test whether sucrose solutions [0% (water control), 1%, 2%, and 3%] applied as a drench to rootstock seedlings before grafting would increase the survival of watermelon grafted using the splice method where both rootstock cotyledons were removed to eliminate meristem tissue and rootstock regrowth. Starch accumulation in rootstock seedlings was the highest for plants that received 3% sucrose solution (71%), followed by plants that received 2% sucrose solution (52%), 1% sucrose solution (29%), and water (6%) (P < 0.0001). Survival (%) of splice-grafted watermelon seedlings 21 days after grafting was the greatest for plants that received 2% and 3% sucrose solution (89% and 82%, respectively), followed by plants that received 1% sucrose solution (78%), and was the lowest for plants that received water (58%) (P < 0.0001). There was a significant interaction due to repeat for both starch accumulation and grafted transplant survival; however, environmental conditions were similar for both repeats: the daily average temperature was 23 °C, the relative humidity (RH) was 64% to 67%, and the daily average light intensity was 224–243 µmol·m−2·s−1. Furthermore, while the vapor pressure deficit from 1:00 to 6:00 pm was 2.49 kPa for repeat 1 and 1.42 kPa for repeat 2, plant survival was greater in repeat 1 than repeat 2. These results indicate that drench applications of sucrose solution to rootstock seedlings before grafting can increase grafting success when both cotyledons are removed from the rootstock before grafting, but further research is needed to optimize the environmental conditions for the survival of grafted plants.
Molecular Characterization of Chinese Grape Landraces (Vitis L.) Using Microsatellite DNA Markers
Authors: Li Beibei , Jiang Jianfu , Fan Xiucai , Zhang Ying , Sun Haisheng , Zhang Guohai , Liu Chonghuai
Published: May 2017

In this study, we present the molecular characterization of 61 Chinese grape landraces and 33 foreign cultivars by using nine microsatellite DNA markers. A total of 115 distinct alleles were amplified, and the average allele number was 12.78. The average observed and expected heterozygosity values were 0.797 and 0.839, respectively. The effective allele numbers ranged from 5.011 to 8.575. The average polymorphism information content (PIC) was 0.816. Eighty distinct genotypes were detected, and new synonyms and homonyms were found. The clustering dendrogram indicated that 94 Vitis materials could be divided into five major groups, and the cluster analysis showed that part of the Chinese grape landraces had a close relationship with the foreign cultivars. Assessment of the true cultivar identity, and the identification of synonyms and homonyms will be a contribution to improve the grape germplasm management and protect breeders’ intellectual rights.
The prevalence of temporomandibular disorders among a group of libyan dental students
Authors: Bugaighis I , Elgehani R , Orafi M , Elatrash A
Published: May 2017

Background: It has been reported that Tempro-Mandibular-disorders (TMD) is the most common orofacial pain source of non-dental origin. The aim of this cross-sectional observational study is to explore the prevalence of signs and symptoms of TMD among a group of dental students in Benghazi-Libya.

Methods: The examined group comprised 100 students [17 males and 83 females; mean age: 24.8±2.23 years. The assessment was undertaken following Helkimo's measures. The prevalence and severity of TMD was determined using a self-reported anamnestic questionnaire and clinical examination. Descriptive statistics was employed to explore the frequencies of the examined variables. Linear correlation coefficient was conducted between the reported symptoms and recorded signs and between the reported symptoms and the clinical dysfunction scores (CDS). The level of significance was set at P<0.05.

Results: A total of 37% of the students reported some level of TMD symptoms [32% mild (Ai1); 5% severe (AiII)]. On the other hand, majority of the students (93%) demonstrated a range of TMD signs [76% mild (DiI); 17% moderate (DiII)]. Although linear correlation coefficient between the reported symptoms (Ai) and the recorded signs (Di) (r=0.32) and between the reported symptoms (Ai) and the CDS (r=0.37) were low, they were statistically significant (P<0.05).

Conclusion: Mild to moderate prevalence of TMD appears to exist among Libyan dental students.
Tailoring cardiovascular risk assessment and prevention for women: One size does not fit all
Authors: Wenger Nanette
Published: May 2017

[first paragraph of article]For many years, cardiovascular disease was considered predominantly a disease of men, despite the fact that more U.S. women than men died annually from cardiovascular illness.1 Because of this misperception of their cardiovascular risk, for many years women were underdiagnosed and undertreated, with consequent increases in cardiovascular morbidity, mortality, and disability. With recent appreciation of this historical gender disparity, clinical and epidemiological research studies have identified cardiovascular features specific to women, resulting in an improved spectrum of care. Although since 1984 more U.S. women than men died annually from cardiovascular disease, beginning in the year 2000 there was a sharp decline in cardiovascular mortality for women, indeed, more precipitous than that for men. Half of this favorable effect is considered due to improved preventive strategies and the remainder to improved management of recognized cardiovascular disease. In 2013, for the first time, more U.S. men than women died of cardiovascular disease and we are delighted to be in second place.
Stability and tracking analysis of gas face seals under low-parameter conditions considering slip flow
Authors: Hu Songtao , Huang Weifeng , Liu Xiangfeng , Wang Yuming
Published: May 2017

Dynamic property of a gas face seal is about an internal ability of the mass-spring-damper system consisting of the nonlinear gas film, the flexible support, and the component mass or moment of inertia to handle ambient disturbances. Stability and tracking properties are important dynamic components, the current research for which mainly focuses on high-speed and high-pressure conditions in turbomachinery applications. In this paper, perturbation theory is used to obtain the linearized properties of the gas film in a spiral groove gas face seal, where the Boltzmann-Reynolds model with Fukui-Kaneko approximation is involved to account for slip flow under low-parameter conditions. Transmissibility of the step jump method is introduced into the perturbation method, and a critical ambient-disturbance amplitude is further proposed to cover the defect of transmissibility in characterizing the tracking property. The effects of slip flow on the stability and tracking properties of gas face seals are explored. The results show that slip flow induces an extra “relaxation region” in the critical transverse moment of inertia, providing a softer demand for angular stability. With regard to transmissibility, slip flow will induce an advantageous effect on transmitting the rotor motion to the stator. However, after considering the space required for tracking motions, the results of critical amplitude indicate that slip flow will induce an extra “rigorous region”, leading gas face seals to require more conservative design and more rigorous manufacture and assembly for non-contacting tracking.
Influence evaluation of wake shedding on natural frequencies of marine propulsion shafts
Authors: Zou Donglin , Zhang Jianbo , Ta Na , Rao Zhushi
Published: May 2017

The calculation of natural frequencies is very significant at the design phase of marine propulsion shafts. And added mass of propellers has high effect on natural frequencies. At present, the effect of wake shedding from the propeller’s trailing edge on added mass is unclear. Then their influence on propulsion shafts natural frequencies is also vague. So in this study, the influence of wake shedding on propellers added mass and propulsion shafts natural frequencies is evaluated. Our results show that first, for the first lateral natural frequency, the max relative error reaches up to 6.52 % if the wake shedding is ignored. So for the lateral vibration, the wake should be considered. Second for the first torsion natural frequency, the max relative error amounts to 5.10 % when the skew angle is 108 degrees. So for the torsion vibration, the wake should also be considered when the skew angle is large. Third, for the axial vibration, the influence of wake is little and may be ignored.
Vibration model of a multi-supported guide bar and analysis on the effect of supports location
Authors: Su Liuyuan , Meng Zhuo , Zhang Yujing , Sun Yize
Published: May 2017

Two methods (equivalent force method and segmental mode assuming method) of calculating the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load is found, considering the structure characteristic of the guide bar, which has long length but small section, and supported by many bearings. The calculation shows that these two methods are convenient for computer programing and have the same results in obtaining the natural frequencies and mode shapes of a free-free-multi-supported beam subjected to an axial load, solving the problem that the vibration function of this kind of beam is hard to deal with because it cannot be simplified with the boundary condition of two ends. Then the segmental mode assuming method is used to analyze the impact of the support location on the natural frequencies and mode shapes of the guide bar. The relation graphs of the natural frequencies with support location, as well as the support locations where the natural frequencies reached the maximum and the minimum are found, providing a reference for the support location selection for the guide bar. The changing curves of the mode shapes with support location are plotted, which show that the bending deformation is homogeneous when the length of each segment is approximately equal, avoiding the phenomenon that bending stresses concentrates at the large-amplitude segments and cause breakage while less stress exists in small-amplitude segments and hinder the exploiting of their performance, providing a reference for the structure design of the guide bar.
Squeal simulation and analysis of brake system with pressure and speed dependent friction model and exerting process of pressure
Authors: Shang Ke , Liu Xiandong , Moureh-Ledig Emmanuel
Published: May 2017

In this paper, a complete finite element model of disc brake considering the ventilated brake disc, pads, back-plate, caliper, bracket, piston, rubber bushes and simplified fluid model driving piston is established. The pressure and speed dependent friction model and temperature field are considered. The results of complex eigenvalue analysis (CEA) show consistence with the existing achievements, thus the feasibility of the established model is verified. Subsequently, the transient dynamic analysis of the brake system is carried out for different exerting process of the pressure which represents the operation of different drivers. Besides, the vibration responses of different brake pressure and different speed are also investigated. The evolution process of the stability is studied by time-frequency analysis (STFT method). Both CEA and time-frequency analysis show the squeal tends to appear in the case of high friction coefficient, low speed and low brake pressure. It can also be found that the vibration frequency and its energy are not constant but fluctuate in a certain range. The results of different pressure exerting processes with simplified fluid model driving piston show that vibration response of disc brake not only depends on the value of brake pressure but also depends on the pressure exerting process. It is supposed that brake pressure and rotational speed determine the frequency of squeal while the process of exerting pressure determines the existing duration of brake squeal.
Hysteresis linearization control of a novel hybrid vibration isolator
Authors: Zhang Yang , Chen Zhaobo , Jiao Yinghou , Wang Xiaoyu
Published: May 2017

The undesired hysteresis exists widely in smart-material actuators, which significantly reduces the accuracy and response speed of the actuators. In this paper, the static experiment of our previously developed hybrid vibration isolator (HVI) employing piezoelectric actuator is implemented to choose appropriate preload of the HVI. The preload-dependent hysteresis of the HVI is also proved in the static experiment. To achieve the hysteresis linearization control of the HVI, two linearization methods named the feedforward linearization and feedforward compensation and PI feedback hybrid linearization control are presented, respectively, which are based on the Bouc-Wen model and corresponding parameter identification model. To evaluate the effectiveness of the proposed linearization controllers for the HVI, the experiments are implemented. The experiment results demonstrate that both linearization controllers for the HVI can linearize the hysteresis characteristics and improve the HVI control accuracy. In addition, the feedforward compensation and PI feedback hybrid linear controller can achieve higher linearity than feedforward compensation controller.
Rolling mill chatter mechanism based on the unsteady lubrication performance
Authors: Liu Xiaochan , Zang Yong , Gao Zhiying , Zeng Lingqiang
Published: May 2017

The unsteady lubrication is one of the major causes for self-excited vibration in rolling. But it is difficult to build a rolling chatter model which considers the unsteady lubrication state in roll bite. Using the regression exponential function model of rolling friction coefficient, a dynamic rolling process model was built. Coupling the dynamic rolling process model with a mill stand structure model, a chatter model which considers the unsteady lubrication state at roll bite was established. Based on the proposed chatter model, the friction coefficient, rolling force and critical velocity of a rolling mill stand under different working conditions were calculated. The computed results were compared to the test results. And it proves the validity of the proposed model. With the proposed chatter model, the effects of rolling process parameters and emulsion lubricant characteristic parameters on friction coefficient and critical velocity were both analyzed and discussed. The chatter model successfully introduces the unsteady friction model into the rolling mill chatter model. It better explains the negative damping effect of the rolling chatter and reflects the rolling mill dynamic vibration characteristic.
Dynamic response analysis in bolted joint structure with viscoelastic layer and experimental investigations
Authors: Liao Xin , Zhang Jianrun , Xu Xiyan , Zhang Cheng
Published: May 2017

In this paper, the dynamic response characteristics of a common double shear lap joint structure with viscoelastic layer are investigated. Firstly, an analytical model is established in shear vibration based on phenomenological model. The fourth order Runge-Kutta method is employed to calculate the harmonic response, where the effect of Coulomb friction and excitation levels on system are presented. Secondly, a new nonlinear finite element model for the bolted joint structure with viscoelastic layer is developed. The simulation results show good agreement with the corresponding experimental results. Finally, the proposed harmonic excitation experiments with laser vibrometer in tangential direction are carried out to investigate the nonlinear behaviors of system, as well as the influence of bolt preload and viscoelastic material on dynamic characteristics of the bolted joint beam. The results show that the viscoelastic layer help reduce vibration at certain extent, especially in the high frequency region of vibration, and some peak frequencies of system can be changed through the viscoelastic layer.
Bifurcation characteristics of torsional-horizontal coupled vibration of rolling mill system
Authors: Liu Shuang , Shi Yatao , Zhang Yunpeng , Zong Meng
Published: May 2017

In this paper, the static bifurcation and dynamic bifurcation of rolling mill system with torsional-horizontal coupling vibration are studied. Firstly, the dynamic equation of torsional-horizontal coupled vibration of rolling mill main drive system is established. Rolling mill is driven by the gear pair, so the torsional vibration of the gear pair, the horizontal vibration and the friction factor are considered in the dynamic equation. Then the equivalent low-dimensional bifurcation equation, which can reveal the system nonlinear characteristics, is obtained using Lyapunov-Schmidt method, and the system static bifurcation characteristics are studied using singularity theory. Lastly, the bifurcation condition and stability of the system with dynamic Hopf bifurcation are studied using Hopf bifurcation theorem. Numerical simulation of the actual parameter values confirms the analytical results.
Modeling and test of flywheel vibration isolation system for space telescope
Authors: Li Lin , Tan Luyang , Lin Kong , Wang Dong
Published: May 2017

Studied on the flywheel micro vibration isolator of a space telescope, the relationship between input and output (I-O) disturbance force and velocity vector is described by the characteristic transfer matrix in the subsystem of the flywheel vibration isolation. The elastic support coupling vibration transfer matrix of the vibration isolator is derived, and the vibration transfer characteristics of the vibration isolation system are studied. The dynamic model of the three degrees coupled vibration isolation system about the flywheel micro vibration excitation, multi elastic support and basic structure is established on the admittance method and partition subsystem. Model simulation and the flywheel vibration isolation system test results show that the two spectra are consistent basically in the frequency components, the form of vortex frequency curve and the change of amplitude, which indicates that the key factors of the vibration characteristics of the flywheel vibration isolation system are accurate and the theoretical analysis is correct. The sub structure analysis method effectively avoids the complexity of the solution of the state vector of the sub structure coupling interface. The elastic support coupled vibration transfer matrix can solve the problem of the sub structure integration and merging, and integrated modeling and analysis in active and passive support system.
Identification of harmonic load acting on an elastically supported thin plate linked with attachments
Authors: Xiao He Ye , Zhao Zhi Jun , Chen Bai Bing , Zhang Hui Ping
Published: May 2017

Plate-like structures in real mechanical system is always simplified and modeled as an elastically restrained thin plate loaded with stiffness or mass. The dynamic model of the plate distinguished with previous classic model is complex vibrational characteristics and merely proposed by numerical method. Accordingly, identification of harmonic load acting on this plate becomes difficult for hardly obtaining inverse equations or matrix from its response functions directly. To solve this problem, dynamic model of the plate is established by numeric method and combined with particle swarm optimization (PSO) method to reconstruct harmonic load by minimizing total error between vibration responses in identification and test. Then, it is used to deal with acceleration responses tested in an elastically supported plate derived by a harmonic load. Parameters of the harmonic load are identified and found to agree with those of real source by their comparison. Thus, it is concluded that harmonic load driving on the plate linked with elastic boundary and attachment can be identified accurately by proposed numeric model of this paper. Furthermore, acceleration distribution of the plate at modal frequencies and responses at different test point, which are acquired from identification and test, are demonstrated and discussed. It is revealed that the numeric model proposed in this paper identifies parameters of harmonic load mainly through tendency of vibration distribution on the plate, and the accuracies of its reconstruction results at some locations are limited.
An adaptive stochastic resonance method for weak fault characteristic extraction in planetary gearbox
Authors: Li Zhixing , Shi Boqiang
Published: May 2017

Planetary gearbox is widely used in rotating machinery and prone to damage and failure due to heavy load and complex operating conditions. Furthermore, due to heavy background noise and complicated transmission path, the fault characteristics imbedded in the acquired signals is very weak and difficult to be extracted. Therefore, it is a challenge task for extracting fault characteristics of planetary gearboxes. To tackle this task, this paper proposes an adaptive stochastic resonance method for weak fault characteristic extraction of planetary gearbox, where a chaos ant colony algorithm characterized global optimization ability is employed to achieve adaptive matching between potential parameters and thereby overcoming the local optimization shortcoming of traditional stochastic resonance. Simulation and planetary gearbox experiments with a missing tooth and broken tooth validate the effectiveness of the proposed method, respectively. The results show that the proposed method is not only able to extract weak fault characteristics but also superior to singular value decomposition method.
Experimental research on behavior of Q420 dual-angle steel with cruciform section under dynamic compression
Authors: Li Buhui , Cao Pingzhou , Zhang Dachang , Guo Yong
Published: May 2017

In order to investigate the mechanical behavior and deformation characteristic of dual-angle steel with cruciform section, this paper presents a series of dynamic compression tests performed on the compound members. The specimens are designed with different width-to-thickness ratios and slenderness ratios. The cruciform plates are used as interconnectors between two components, with three or four bolts connecting each face and angle limb. The experimental results indicate that the failure mode of core members is a mixture of flexural buckling and local instability. The internal force distribution of two sub-members is asymmetric, with the ratios varying from 1.04 to 1.31. A simplified finite element model is then developed to stimulate their experimental behavior. The analytical model is verified by experimental results and proved to be precise and reliable. Moreover, the theoretical analysis is performed to investigate the critical stresses due to different buckling modes. The bearing capacity predicted by Chinese standard is proved to be not conservative, on this basis, a modified design approach is proposed, and the design capacities fit the test data well.
Blind source separation of rolling element bearing’ single channel compound fault based on Shift Invariant Sparse Coding
Authors: Wang Hongchao , Li Liwei , Gong Xiaoyun , Du Wenliao
Published: May 2017

The mechanical vibration source signal collected by sensor often includes a variety of internal vibration source of contributions such as gears, bearings, shaft and so on. It is often hoped to achieve effective separation of the source signal in order to obtain better fault diagnosis result. Blind source separation of the failure signal of rolling element bearing is a challenging task due to the above reasons, especially in the case of single channel compound fault. A method of blind source separation of rolling element bearing’s single channel compound fault based on Shift-Invariant Sparse Coding (SISC) is proposed in the paper. The waveform characteristic of different fault signal has some difference in the structure even that the same impulse characteristics of signals are produced by different parts, and the difference can be captured by the SISC method with the following reasons: Firstly, a set of basis functions is trained and obtained by SISC feature self-study method (The number of the basis functions is big necessarily). Then the potential components are constructed using the corresponding obtained basis functions. At last, the clustering operation is carried out using the structural similarity of the potential components, and the clustering signals represent the different vibration source signals. Apply the traditional vibration signal handling method such as envelope demodulation to the obtained clustering signals respectively and better fault diagnosis results are obtained at last.
Excitation of 2D resonant oscillations in piezoelectric plate with additional masses
Authors: Bansevičius Ramutis , Navickaitė Sigita , Jūrėnas Vytautas , Mažeika Dalius , Žvironienė Aušra
Published: May 2017

This article presents results of investigation of piezoelectric transducer which consists of rectangle homogeneous piezoceramic plate with two additional masses glued on the top surface of the transducer. Because of additional masses and a certain sectioning of piezoelectric electrodes, the vibration forms of the plate and resonant frequencies are changed, therefore, the plate generates 3D longitudinal and bending vibrations. Numerical and experimental investigation showed that the masses glued at the surface of piezoelectric plate obtain elliptical trajectories of motion when the first mode of longitudinal vibrations of the plate is excited. Such form of vibrations of the masses enables using them for various piezoelectric drive mechanisms as contact elements and to transform high-frequency vibrations into the directional or rotational movement of the rotor or slider. In order to examine the deformations and dynamic characteristics of the homogenous piezoelectric plate with two additional masses, the numerical modelling of such piezo transducer and the experimental study have been carried out.
Dynamic response analysis of intake tower in hydroelectric power station with high surrounding rock
Authors: Dang Kangning , Liu Yunhe , Zhang Jingyi
Published: May 2017

This paper presents results of numerical analysis for the seismic response of hydropower station intake tower in step-like ground based on artificial boundary theory. A L topography finite element model was established to verify the correctness of the proposed method of viscous elasticity boundary by consider inconsistent reflective surface. The method was applied to an intake tower, and the acceleration of bedrock was obtained by seismic inversion method, then the equivalent load of each node was calculated. Five different models were established as follow: massless foundation, consistent input viscous elasticity boundary, inconsistent input viscous elasticity boundary and whether set contact, then displacement and stress were compared, the results show that the proposed method with contact was minimal. The base plate of intake tower and the foundation were in close adhesion state in the whole process of earthquake, both sides and rear side of intake tower without through disengagement phenomena from rock, it can conclude that the intake tower in the overall stability state.
A fuzzy logic controller for optimal structural control using MR dampers and particle swarm optimization
Authors: Zabihi Samani Masoud , Ghanooni-Bagha Mohammad
Published: May 2017

Control devices can be used to dissipate the energy and attenuate undesirable vibration on engineering structures. Recently, to mitigate the response of structures during the earthquakes and high intensity winds, semi active control has been widely used. MR dampers are semi active control devices that are managed by sending external voltage supply. A new adaptive fuzzy logic controller (FLC) is introduced to manage MR damper intelligently. Furthermore, a novel evolutionary algorithm of particle swarm optimization (PSO) was used to optimize the placement and the number of MR dampers and sensors in the sense of minimum resultant vibration magnitude. Numerical efforts were considered to validate the efficiency of proposed FLC. In designer’s point of view, the proposed PSO-FLC controller can find the optimal solutions during a reasonable number of iterations. Finally, results demonstrate that proposed PSO-FLC controller could find the appropriate control force and attenuates the excessive responses in several buildings.
Influence of vertical and horizontal whole-body vibration on some psychomotor and cognitive functions of employees age 50+ (pilot study)
Authors: Kowalski Piotr , Zając Jacek
Published: May 2017

This paper presents the pilot study on influence of vertical and horizontal vibration on some psychomotor and cognitive functions of employees at the age of 50+. Tests have been conducted in two series on special designed laboratory test bench for simulation of exposure to whole-body vibration. During the I series of tests, vertical vibration had acted on subjects and during II series horizontal lateral vibration had acted. Complex reaction time values obtained during I and II series indicates that there are no statistical significant differences between reaction of subjects on vertical and horizontal vibration. However slightly lower values during II series were noticed. Similar observations regarded results of cognitive function (attention and perceptiveness) tests.
Numerical analysis and optimization of noises of ship cabins in the low frequency
Authors: Xu Yan-lei , Huang Xiao-shan , Zhu Long-tu , Huang Dong-yan
Published: May 2017

Ship cabins are places for the crew to be on duty and have a rest. The convention sets a high limitation for noises of ship cabins. This paper combined finite element method with boundary element method to study and improve the noise of ship cabins. Firstly, this paper established the finite element model of a ship cabin, computed structural response, took the structural response as boundary condition and input it into acoustic software to couple with boundary element model, realize the computation of vibro-acoustic coupling and obtain sound pressure response. Then, the numerically computational sound pressure was compared with experimental results, and a good consistency was presented. It showed that the vibro-acoustic coupling model of the ship cabin in this paper was effective. In addition, this paper also computed the noise contribution of cabin panels to observation points and obtained panels which had a serious contribution to cabin noises. Finally, this paper applied laminated plate structure to these panels and recomputed cabin noises to compare with the original structure. Results showed that peak noises of field points were obviously improved, which ensured that the noise level of ship cabins satisfied the corresponding requirements of the convention.
Analysis on the aerodynamic behavior and noises of the cross section of the cable tower for long-span bridges
Authors: Dong Fenghui
Published: May 2017

Cable towers are an important aerodynamic noise source of long-span bridges. The flow effect of various parts of the cable tower on airflow will cause large aerodynamic noises and thus influence environments. This paper conducted on research on the cross-sectional structure of the cable tower of long-span bridges, built a computational model of aerodynamic noises for cable towers of long-span bridges with original rectangular cross section and improved cross section. The computational fluid dynamics was adopted to analyze the non-steady flow of cable towers, and the numerical value of aerodynamic noises was predicted based on Lighthill’s acoustic analogy. Then, acoustic BEM was also adopted to study radiation noises of cable towers in the far-field. Results showed that improved cable tower could reduce the dispersion degree of airflow and weaken Karman Vortex Street. Aerodynamic noises induced by cable towers with improved cross section mainly radiated in a direction perpendicular to airflow, and the directivity of noises was obvious. Sound pressure level (SPL) of aerodynamic noises of cable towers with improved cross section was 4.2 dBA less than that of initial rectangular cross section in the far-field, which showed obvious effect on noise reduction. In the meanwhile, this paper studied the mechanism of main frequency at various parts of cable towers with improved cross section and discussed the reason of noise reduction, whose research achievements could provide design basis for generation mechanism and reduction of aerodynamic noises of cable towers of long-span bridges.
Analytical analysis on damping characteristics of rotor system
Authors: Wu Min , Yang Shengbo , Bao Wen , Yang Jinfu
Published: May 2017

A general vibration model of a flexible rotor system is established to investigate the influences of the damping characteristics on vibration behaviors. Based on the multi-scale method, the analytical solutions of steady-state and transient-state are derived under the positive and negative conditions of nonlinear damping. The physical significance of the coefficients and their influences on rotor behaviors are analyzed through theoretical analysis and numerical calculation. The experimental results elaborate the damping effect and verify the rationality of the model.
Transvaginal ultrasound - noninvasive method for the prediction of response to concurrent chemoradiotherapy in cases of cervical cancer
Authors: Celiesiute J. , Gaurilcikas A. , Gedgaudaite M. , Paskauskas S. , Jariene K. , Vaitkiene D.
Published: May 2017

The objective of this paper is to study the differences in tumor size, color score and Doppler indices prior, during and after the treatment with concurrent chemoradiotherapy in cases of locally advanced cervical carcinoma and to predict the response to the treatment. The study group comprised fifty-two patients with histologically confirmed invasive carcinoma of the cervix. All patients were scheduled for concurrent chemoradiotherapy and were assessed by transvaginal ultrasound before the initiation, before 4th course of chemotherapy and 3 months after the therapy. Maximum cervical tumor length, anterior-posterior diameter and width have been measured and tumor volume was calculated. Complete clinical response (CR) was defined when no residual tumor was found. Partial clinical response (PR) was determined when the tumor volume had decreased more than 50 %. Intratumoral blood flow was subjectively evaluated by Color Doppler examination, the lowest resistance index (RI) and the highest peak systolic velocity (PSV) were used for the analysis. The results of this study demonstrate that transvaginal ultrasound is a valuable non-invasive diagnostic tool for the assessment of the response to concurrent chemoradiotherapy in cases of advanced cervical cancer.