bluuebunny/crossref_metadata_2025 huggingface dataset:
Correlations Between Digital Planimetry and Optical Coherence Tomography, Confocal Scanning Laser Ophthalmoscopy in Assessment of Optic Disc Parameters
Authors: Buteikienė Dovilė , Paunksnis Alvydas , Barzdžiukas Valerijus , Žaliūnienė Dalia , Balčiūnienė Jūratė , Jegelevičius Darius
Published: April 2018

Objective and Aim. In routine clinical practice, laser methods for the evaluation of optic disc parameters are expensive and not accessible for all ophthalmologists; therefore, there is a need for less expensive technique. The aim of this study was to assess correlations between the parameters of the optic disc measured by digital planimetry (DP), optical coherence tomography (OCT), and confocal scanning laser ophthalmoscopy (CSLO) in healthy and glaucoma patients with the normal biometric parameters of the eye. Material and Methods. This case-control study enrolled 40 patients with glaucoma and 32 healthy patients with the normal biometric parameters of the eye. All subjects underwent full ophthalmologic examination, digital color optic disc photography, OCT, and CSLO at the same visit. The optic disc was morphometrically analyzed by DP, OCT, and CSLO. Seven optic disc parameters were evaluated. Results. In the glaucoma group, the optic disc and cup areas (r=0.7–0.8, P<0.001) and cup-tooptic disc and rim-to-optic disc area ratios (r=0.7, P<0.001) measured by DP were strongly correlated with those measured by OCT and CSLO, while the horizontal and vertical cup-to-optic disc diameter ratios were found to be moderately correlated (r=0.6–0.7, P<0.001). In healthy patients, the optic disc and cup areas were strongly correlated (r=0.7–8.0, P<0.001). Significant differences in all optic disc parameters, except for the optic disc area, measured by DP, OCT, and CSLO were found between glaucoma and healthy patients. Conclusions. Strong correlations between the parameters of the optic disc measured by DP, OCT, and CSLO were found. There were significant differences in the parameters between healthy and glaucoma eyes measured using DP; therefore, this technique may be used for diagnosis, management, and screening of glaucoma.
Factors Influencing Women’s Preference to Select a Combined Hormonal Contraceptive Method: A Cross-Sectional Survey in Lithuania
Authors: Čepulienė Ramona , Sveikatienė Renata , Gutauskas Kęstutis , Vanagienė Virginija
Published: April 2018

Background and Objective. Effectiveness and side effects are the main concerns when selecting a contraceptive method. Therefore, the aim of this study was to identify the preference of a combined hormonal contraception method by Lithuanian women, the reasons for selecting one of them and rejecting other two methods, and the factors determining selection or rejection. Material and Methods. A cross-sectional multicenter survey was performed by the Lithuanian Society of Private Obstetricians and Gynecologists. A total of 4134 women, aged 18–49, who visited their physician due to initiation or reinitiation of hormonal contraception completed self-administered questionnaires identifying the reasons to select one method and reject the two remaining ones. Descriptive and inferential statistics methods were used for data analysis. Results. The vaginal ring was the most accepted contraception method (55.4%), followed by the pill (35.6%). The skin patch was least preferable (9%). The vaginal ring and the skin patch were mainly selected for the frequency of use (72.9% and 51.2%, respectively), convenience (48.5% and 71%, respectively), and lower probability of noncompliance (48.7% and 63.5%, respectively). The main reason for selecting the pill was familiarity with the method (50.7%). The acceptance of vaginal ring increased with age and was higher among women with higher education. Conclusions. The most important factors when selecting a contraceptive method among the methods with equal effectiveness and similar safety profile were convenience, frequency of use, and lower probability of noncompliance. Age, education, and employment status were found to be other reasons associated with the choice of contraceptive method.
Incidence of Inflammatory Bowel Disease in Kaunas Region, Lithuania
Authors: Kiudelis Gediminas , Jonaitis Laimas , Adamonis Kęstutis , Žvirblienė Aida , Tamelis Algimantas , Kregždytė Rima , Kučinskienė Rūta , Šventoraitytė Jurgita , Kupčinskas Limas
Published: April 2018

Objective. The aim of this study was to evaluate the incidence of inflammatory bowel disease in Kaunas and its region during a 3-year period. Material and Methods. The study was conducted during the 3-year period (2007–2009) and enrolled the patients from Kaunas with its region, which has a population of 381 300 inhabitants. The data were collected from all practices in the area where the diagnosis of inflammatory bowel disease was made by practicing gastroenterologists and consulting pediatricians along with endoscopists. Only new cases of inflammatory bowel disease were included into analysis. The diagnosis of ulcerative colitis and Crohn’s disease was strictly made according to the Copenhagen criteria. Age- and sex-standardized incidence was calculated for each year of the study period. Results. A total of 108 new inflammatory bowel disease cases were diagnosed during the study period: 87 had ulcerative colitis, 16 Crohn’s disease, and 5 indeterminate colitis. The incidence of ulcerative colitis, Crohn’s disease, and indeterminate colitis for each study year was 6.85, 5.33, and 7.38 per 100 000; 0.95, 1.11, and 1.57 per 100 000; and 0.47, 0.21, and 0.42 per 100 000, respectively. The average 3-year standardized incidence of ulcerative colitis, Crohn’s disease, and indeterminate colitis was 6.52, 1.21, and 0.37 per 100 000, respectively. The mean patients’ age at onset of ulcerative colitis, indeterminate colitis, and Crohn’s disease was 49.95 (SD, 17.03), 49.80 (SD, 17.71), and 34.94 years (SD, 0.37), respectively. Conclusions. The average 3-year incidence of ulcerative colitis in Kaunas region was found to be lower as compared with that in many parts of Central and Western Europe. The incidence of Crohn’s disease was low and very similar to other countries of Eastern Europe. Age at onset of the diseases appeared to be older than that reported in the Western industrialized countries.
Parametric Excitation of Optomechanical Resonators by Periodical Modulation
Authors: Huang Jianguo , Karim Muhammad Faeyz , Wu Jiuhui , Chen Tianning , Liu Aiqun
Published: April 2018

Optical excitation of mechanical resonators has long been a research interest, since it has great applications in the physical and engineering field. Previous optomechanical methods rely on the wavelength-dependent, optical anti-damping effects, with the working range limited to the blue-detuning range. In this study, we experimentally demonstrated the excitation of optomechanical resonators by periodical modulation. The wavelength working range was extended from the blue-detuning to red-detuning range. This demonstration will provide a new way to excite mechanical resonators and benefit practical applications, such as optical mass sensors and gyroscopes with an extended working range.
A Sparse-Driven Anti-Velocity Deception Jamming Strategy Based on Pulse-Doppler Radar with Random Pulse Initial Phases
Authors: Liu Zhen , Sui Jinping , Wei Zhenhua , Li Xiang
Published: April 2018

This paper focuses on developing an anti-velocity jamming strategy that enhances the ability of a pulse-Doppler (PD) radar to detect moving targets in the presence of translational and/or micro motion velocity jamming generated by the digital radio frequency memory (DRFM) repeat jammers. The strategy adopts random pulse initial phase (RPIP) pulses as its transmitted signal and thus gets DRFM jammers not adaptable to the randomness of initial phase of the transmitted pulses in the pulse repetition interval (PRI) domain. The difference between the true target echo and the false target jamming signal at each PRI is then utilized to recognize the true and false target signals. In particular, an entropy based multi-channel processing scheme is designed to extract the information of the received signal without the assumption that true and false targets must be both included within one coherent processing interval (CPI). Information such as the component of the received signal (target echo only, jamming only or both) or the operating manner of DRFM repeat jammer can be gained (if jamming exists). Meanwhile, we solve the false target recognition problem under sparse theory frame and our previous work named the short-time sparse recovery (STSR) algorithm is introduced to recover the motion parameters of the true and/or false targets in the time-frequency domain. It should be pointed out that both the translational false target jamming and micro motion target jamming can be recognized in our strategy. The performance of the proposed strategy is compared with the correlated processing (CP) method used by most extant strategies. It is shown that the proposed strategy can successfully recognize the existence of true and/or false targets and keep its power in recovering corresponding motion parameters even when the jamming environment is strong.
Non-Contact Smartphone-Based Monitoring of Thermally Stressed Structures
Authors: Sefa Orak Mehmet , Nasrollahi Amir , Ozturk Turgut , Mas David , Ferrer Belen , Rizzo Piervincenzo
Published: April 2018

The in-situ measurement of thermal stress in beams or continuous welded rails may prevent structural anomalies such as buckling. This study proposed a non-contact monitoring/inspection approach based on the use of a smartphone and a computer vision algorithm to estimate the vibrating characteristics of beams subjected to thermal stress. It is hypothesized that the vibration of a beam can be captured using a smartphone operating at frame rates higher than conventional 30 Hz, and the first few natural frequencies of the beam can be extracted using a computer vision algorithm. In this study, the first mode of vibration was considered and compared to the information obtained with a conventional accelerometer attached to the two structures investigated, namely a thin beam and a thick beam. The results show excellent agreement between the conventional contact method and the non-contact sensing approach proposed here. In the future, these findings may be used to develop a monitoring/inspection smartphone application to assess the axial stress of slender structures, to predict the neutral temperature of continuous welded rails, or to prevent thermal buckling.
Development and Testing of an Integrated Rotating Dynamometer Based on Fiber Bragg Grating for Four-Component Cutting Force Measurement
Authors: Liu Mingyao , Bing Junjun , Xiao Li , Yun Kang , Wan Liang
Published: April 2018

Cutting force measurement is of great importance in machining processes. Hence, various methods of measuring the cutting force have been proposed by many researchers. In this work, a novel integrated rotating dynamometer based on fiber Bragg grating (FBG) was designed, constructed, and tested to measure four-component cutting force. The dynamometer consists of FBGs that are pasted on the newly designed elastic structure which is then mounted on the rotating spindle. The elastic structure is designed as two mutual-perpendicular semi-octagonal rings. The signals of the FBGs are transmitted to FBG interrogator via fiber optic rotary joints and optical fiber, and the wavelength values are displayed on a computer. In order to determine the static and dynamic characteristics, many tests have been done. The results show that it is suitable for measuring cutting force.
HOMOGENIZATION OF ELASTIC PLATE EQUATION∗
Authors: Burazin Krešimir , Jankov Jelena , Vrdoljak Marko
Published: April 2018

We are interested in general homogenization theory for fourth-order elliptic equation describing the Kirchhoﬀ model for pure bending of a thin solid symmetric plate under a transverse load. Such theory is well-developed for second-order elliptic problems, while some results for general elliptic equations were established by Zhikov, Kozlov, Oleinik and Ngoan (1979). We push forward an approach of Antoni´c and Balenovi´c (1999, 2000) by proving a number of properties of H-convergence for stationary plate equation.
ON NUMERICAL SIMULATION OF ELECTROMAGNETIC FIELD EFFECTS IN THE COMBUSTION PROCESS
Authors: Kalis Harijs , Marinaki Maksims , Strautins Uldis , Zake Maija
Published: April 2018

This paper deals with a simpliﬁed model taking into account the interplay of compressible, laminar, axisymmetric ﬂow and the electrodynamical eﬀects due to Lorentz force’s action on the combustion process in a cylindrical pipe. The combustion process with Arrhenius kinetics is modelled by a single step exothermic chemical reaction of fuel and oxidant. We analyze non-stationary PDEs with 6 unknown functions: the 3 components of velocity, density, concentration of fuel and temperature. For pressure the ideal gas law is used. For the inviscid ﬂow approximation ADI method is used. Some numerical results are presented.
The First Data Release from SweetSpot: 74 Supernovae in 36 Nights on WIYN+WHIRC
Authors: Weyant Anja , Wood-Vasey W. M. , Joyce Richard , Allen Lori , Garnavich Peter , Jha Saurabh W. , Kroboth Jessica R. , Matheson Thomas , Ponder Kara A.
Published: April 2018

SweetSpot is a 3 yr National Optical Astronomy Observatory (NOAO) survey program to observe Type Ia supernovae (SNe Ia) in the smooth Hubble flow with the WIYN High-resolution Infrared Camera (WHIRC) on the WIYN 3.5 m telescope. We present data from the first half of this survey, covering the 2011B–2013B NOAO semesters and consisting of 493 calibrated images of 74 SNe Ia observed in the rest-frame near-infrared (NIR) in the range 0.02 < z < 0.09. Because many observed supernovae require host-galaxy subtraction from templates taken in later semesters, this release contains only the 186 NIR (JHK

s
) data points for the 33 SNe Ia that do not require host-galaxy subtraction. The sample includes four objects with coverage beginning before the epoch of B-band maximum and 27 beginning within 20 days of B-band maximum. We also provide photometric calibration between the WIYN+WHIRC and Two Micron All-Sky Survey (2MASS) systems, along with light curves for 786 2MASS stars observed alongside the SNe Ia. This work is the first in a planned series of three SweetSpot Data Releases. Future releases will include the full set of images from all 3 yr of the survey, including host-galaxy reference images and updated data processing with host-galaxy reference subtraction. SweetSpot will provide a well-calibrated sample that will help improve our ability to standardize distance measurements to SNe Ia, examine the intrinsic optical–NIR colors of SNe Ia at different epochs, explore the nature of dust in other galaxies, and act as a stepping-stone for more distant, potentially space-based surveys.
Characterizing Earth Analogs in Reflected Light: Atmospheric Retrieval Studies for Future Space Telescopes
Authors: Feng Y. Katherina , Robinson Tyler D. , Fortney Jonathan J. , Lupu Roxana E. , Marley Mark S. , Lewis Nikole K. , Macintosh Bruce , Line Michael R.
Published: April 2018

Space-based high-contrast imaging mission concepts for studying rocky exoplanets in reflected light are currently under community study. We develop an inverse modeling framework to estimate the science return of such missions given different instrument design considerations. By combining an exoplanet albedo model, instrument noise model, and ensemble Markov chain Monte Carlo sampler, we explore retrievals of atmospheric and planetary properties for Earth twins as a function of signal-to-noise ratio (S/N) and resolution (R). Our forward model includes Rayleigh-scattering, single-layer water clouds with patchy coverage, and pressure-dependent absorption due to water vapor, oxygen, and ozone. We simulate data at R = 70 and 140 from 0.4 to 1.0 μm with S/N = 5, 10, 15, and 20 at 550 nm (i.e., for HabEx/LUVOIR-type instruments). At these same S/Ns, we simulate data for WFIRST paired with a starshade, which includes two photometric points between 0.48 and 0.6 μm and R = 50 spectroscopy from 0.6 to 0.97 μm. Given our noise model for WFIRST-type detectors, we find that weak detections of water vapor, ozone, and oxygen can be achieved with observations with at least R = 70/S/N = 15 or R = 140/S/N = 10 for improved detections. Meaningful constraints are only achieved with R = 140/S/N = 20 data. The WFIRST data offer limited diagnostic information, needing at least S/N = 20 to weakly detect gases. Most scenarios place limits on planetary radius but cannot constrain surface gravity and, thus, planetary mass.
Iron and Silicate Dust Growth in the Galactic Interstellar Medium: Clues from Element Depletions
Authors: Zhukovska Svitlana , Henning Thomas , Dobbs Clare
Published: April 2018

The interstellar abundances of refractory elements indicate a substantial depletion from the gas phase, which increases with gas density. Our recent model of dust evolution, based on hydrodynamic simulations of the life cycle of giant molecular clouds (GMCs), proves that the observed trend for [Sigas/H] is driven by a combination of dust growth by accretion in the cold diffuse interstellar medium (ISM) and efficient destruction by supernova (SN) shocks. With an analytic model of dust evolution, we demonstrate that even with optimistic assumptions for the dust input from stars and without destruction of grains by SNe it is impossible to match the observed [Sigas/H]–n
H relation without growth in the ISM. We extend the framework developed in our previous work for silicates to include the evolution of iron grains and address a long-standing conundrum: “Where is the interstellar iron?” Much higher depletion of Fe in the warm neutral medium compared to Si is reproduced by the models, in which a large fraction of interstellar iron (70%) is locked as inclusions in silicate grains, where it is protected from efficient sputtering by SN shocks. The slope of the observed [Fegas/H]–n
H relation is reproduced if the remaining depleted iron resides in a population of metallic iron nanoparticles with sizes in the range of 1–10 nm. Enhanced collision rates due to the Coulomb focusing are important for both silicate and iron dust models to match the slopes of the observed depletion–density relations and the magnitudes of depletion at high gas density.
Effects of Fallback Accretion on Protomagnetar Outflows in Gamma-Ray Bursts and Superluminous Supernovae
Authors: Metzger Brian D. , Beniamini Paz , Giannios Dimitrios
Published: April 2018

Rapidly spinning, strongly magnetized protoneutron stars (“millisecond protomagnetars”) are candidate central engines of long-duration gamma-ray bursts (GRBs), superluminous supernovae (SLSNe), and binary neutron star mergers. Magnetar birth may be accompanied by the fallback of stellar debris, lasting for seconds or longer following the explosion. Accretion alters the magnetar evolution by (1) providing an additional source of rotational energy (or a potential sink, if the propeller mechanism operates), (2) enhancing the spin-down luminosity above the dipole rate by compressing the magnetosphere and expanding the polar cap region of open magnetic field lines, and (3) supplying an additional accretion-powered neutrino luminosity that sustains the wind baryon loading, even after the magnetar’s internal neutrino luminosity has subsided. The more complex evolution of the jet power and magnetization of an accreting magnetar more readily accounts for the high 56Ni yields of GRB SNe and the irregular time evolution of some GRB light curves (e.g., bursts with precursors followed by a long quiescent interval before the main emission episode). Additional baryon loading from accretion-powered neutrino irradiation of the polar cap lengthens the time frame over which the jet magnetization is in the requisite range σ ≲ 103 for efficient gamma-ray emission, thereby accommodating GRBs with ultralong durations. Though accretion does not significantly raise the maximum energy budget from the limit of ≲ few × 1052 erg for an isolated magnetar, it greatly expands the range of magnetic field strengths and birth spin periods capable of powering GRB jets, reducing the differences between the magnetar properties normally invoked to explain GRBs versus SLSNe.
A Comprehensive Catalog of Galactic Eclipsing Binary Stars with Eccentric Orbits Based on Eclipse Timing Diagrams
Authors: Kim C.-H. , Kreiner J. M. , Zakrzewski B. , Ogłoza W. , Kim H.-W. , Jeong M.-J.
Published: April 2018

A comprehensive catalog of 623 galactic eclipsing binary (EB) systems with eccentric orbits is presented with more than 2830 times of minima determined from the archived photometric data by various sky-survey projects and new photometric measurements. The systems are divided into two groups according to whether the individual system has a GCVS name or not. All the systems in both groups are further classified into three categories (D, A, and A+III) on the basis of their eclipse timing diagrams: 453 D systems showing just constantly displaced secondary minima, 139 A systems displaying only apsidal motion (AM), and 31 A+III systems exhibiting both AM and light-time effects. AM parameters for 170 systems (A and A+III systems) are consistently calculated and cataloged with basic information for all systems. Some important statistics for the AM parameters are discussed and compared with those derived for the eccentric EB systems in the Large and Small Magellanic Clouds.
On the Jet Properties of γ-Ray-loud Active Galactic Nuclei
Authors: Chen Liang
Published: April 2018

Based on broadband spectral energy distributions (SEDs), we estimate the jet physical parameters of 1392 γ-ray-loud active galactic nuclei (AGNs), the largest sample so far. The (SED) jet power and magnetization parameter are derived for these AGNs. Out of these sources, the accretion disk luminosity of 232 sources and (extended) kinetic jet powers of 159 sources are compiled from archived papers. We find the following. (1) Flat-spectrum radio quasars (FSRQs) and BL Lacs are well separated by

in the γ-ray luminosity versus photon index plane with a success rate of 88.6%. (2) Most FSRQs present a (SED) jet power larger than the accretion power, which suggests that the relativistic jet-launching mechanism is dominated by the Blandford–Znajek process. This result confirms previous findings. (3) There is a significant anticorrelation between jet magnetization and a ratio of the (SED) jet power to the (extended) kinetic jet power, which, for the first time, provides supporting evidence for the jet energy transportation theory: a high-magnetization jet may more easily transport energy to a large scale than a low-magnetization jet.
Prognostics Methods of Security Phenomena
Authors: Smolík Josef
Published: April 2018

This article describes the basic terms used in prognostics (future studies, forecasting the future, prognosis, prediction, expert) and introduces selected prognostic methods and techniques which could be applied in security area (brainstorming, focus group, trend extrapolation, Delphi method, scenarios etc.). The basic classifications and prognosis typologies are mentioned as well. Particular phases of prognosis making are described too. For the Czech security community the prognosis making has an important potential whose outcomes (of particular surveys) should be manifest in following years. This text has only tried to outline selected methods and techniques for their potential application.
Species conservation profile of moths (Insecta, Lepidoptera) from Azores, Portugal
Authors: Borges Paulo , Pérez Santa-Rita Jose , Nunes Rui , Danielczak Anja , Hochkirch Axel , Amorim Isabel , Lamelas-Lopez Lucas , Karsholt Ole , Vieira Virgílio
Published: April 2018

The few remnants of Azorean native forests harbour a unique set of endemic moths (Insecta, Lepidoptera), some of them under severe long term threats due to small sized habitats or climatic changes. In this contribution, we present the IUCN Red List profiles of 34 endemic moths to the Azorean archipelago, including species belonging to two diverse families: Noctuidae (11 species) and Crambidae (eight species). The objective of this paper is to assess all endemic Azorean moth species and advise on possible future research and conservation actions critical for the long-trem survival of the most endangered species.

Most species have a large distribution (i.e. 58% occur in at least four islands), very large extent of occurrence (EOO) and a relatively large area of occupancy (AOO). Only nine species are single-island endemics, three of them from Flores, three from São Miguel and one from Pico, São Jorge and Faial. Most of the species also experience continuing decline in habitat quality, number of locations and subpopulations caused by the ongoing threat from pasture intensification, forestry, invasive plant species and future climatic changes. The lack of new records may indicate that one of the species previously named is extinct (Eupithecia ogilviata). Therefore, we suggest as future conservation actions: (1) a long-term species monitoring plan and (2) control of invasive species.
Study on Multi-Step Spinning Process for Disk-Like Part with Thickened Rim
Authors: Jin Jun Song , Su Xue Dong , Wang Xin Yun , Deng Lei
Published: April 2018

This paper studies the process of a five-step spinning to thicken the edge of the disc-like part. By using finite element simulation and experiment, the sectional shape and flow-line distribution of the rim were studied. The results showed that the flow lines of the cross-section of the formed part are distributed along the shape of the part. The disc-like part with thickened rim can be well formed by a multi-step spinning process. A large bottom radian of roller groove can lead a folding in the first step and a reduced r can overcome the folding. An over-small angle αin step 2 will lead a pit defect, it can be solved by increasing the angle.
Micro-Drawing of Circular Cups with Thin Stainless Steel Sheets
Authors: Su Hong Syuan , Chen Fuh Kuo , Huang Kun Min
Published: April 2018

With the ongoing development of product process, there is a growing demand on micro products. Though the macro-drawing process has been well-developed, the design concepts may not be directly applicable to the micro-drawing due to the size effect occurred in the micro-forming processes. In the present study, experiments were conducted first to establish the stress-strain curves, r-values and work hardening exponents of 304 stainless steel sheets with different grain sizes. The experiment results reveal that the stress-strain and r-value become smaller and the work hardening exponent increases for larger grain sizes. The difference between stress-strain curves in various directions of 0°, 45° and 90°, respectively, is significant when the grain size increases. The stamping of a vibration motor shell of cell phone, which bears a circular cylindrical shape, was also examined in the present study. The finite element simulations were performed to evaluate the formability of the multi-stage drawing process with initial die design. The forming characteristics were identified and an optimum die design was then developed with the use of the finite element analysis. The stamping process with multi-stage tooling design based on the finite element analysis was implemented and the actual stamping experiments were conducted to verify finite element analysis. The experimental results confirm the validity of the modified tooling design and the efficiency of the finite element analysis.
Evolution of White Layer during Wire-Cutting and Comparison of Several Methods to Improve Surface Integrity for Fineblanking Tools
Authors: Zhang Xiang Lin , Peng Han Lin , Zhang Li Yun , Cao Chuan Liang , Yi Jing Wen , Zhou Yu , Zhang Yu
Published: April 2018

Powder metallurgical high speed steel (such as S390) has superior mechanical properties and been used as fineblanking tools. The electrical discharge machining has been widely used for cutting fine blanking tools which are made of especially hard tool steels. Whereas, its thermal nature causes great concerns regarding surface integrity, which matters a lot to tool life. In the present study, the evolution of surface integrity of the S390 with multi-cutting is comprehensively compared. The result shows that the surface roughness, white layer thickness and surface residual stress decrease with the increase of cutting pass. Additionally, the effectiveness to remove white layer on HSS S390 by manual and towed polishing and electrolytic polishing are compared. At last, a device of abrasive water jet polishing is designated to remove the white layer resulted from wire-cutting.
Experimental and Numerical Analysis of Titanium Alloy Microtube Tube-End Nosing Forming
Authors: Chen Chien Yi , Chen Tsung Chia
Published: April 2018

This study is mainly based on five sets of mold cone angle and friction coefficient of micro-tube tube end necking forming analysis, and the tool cone angle of 60° experimental verification is carried out to analyze the titanium alloy (Grade 1) micro-tube for different mold cone angle and the different friction coefficient caused by the difference between the shrinkage forming. In this paper, Prandtl-Reuss's plastic flow rule, combined with finite element deformation theory and updated Lagrangian formulation (ULF) concept, establish an incremental elasto-plastic finite element analysis program for simulating the miniature tube end necking. The forming process also uses the generalized rmin algorithm to deal with elasto-plastic state and contact problems. From the simulation data of necking process, deformation history, punch load and punch stroke, stress and strain distribution is obtained. The analysis results show that by increasing the mold cone angle and friction coefficient, the thickness tends to be thicker in the certain area.
Ideal Flow Theory of Pressure-Dependent Materials for Design of Metal Forming Processes
Authors: Alexandrov Sergei , Mokryakov Viacheslav , Date Prashant
Published: April 2018

The ideal flow theory for pressure-dependent materials is used to calculate an ideal die for plane strain extrusion/drawing. In particular, the double slip and rotation and double shearing model are adopted. Comparison with the available ideal flow solution for pressure – independent material is made. It is shown that the die for pressure-dependent material is shorter than that for pressure-independent material. Moreover, the angle of internal friction has an effect of the distribution of contact pressure.
Microstructure and Texture Evolution of 2024 Aluminum Alloy Sheet under Different Loading Conditions
Authors: Zhou Peng , Deng Lei , Wang Xin Yun
Published: April 2018

To study microstructure and texture evolution of 2024 aluminum alloy sheet under different loading conditions, thermal tensile and compression experiments of 2024 aluminum alloy rolled sheets were carried out at temperatures ranging from 300 °C to 450 °C and under strain rates ranging from 0.001 s-1 to 0.1 s-1. During tensile deformation, the HABs of original grains are directly elongated until abruption. DRX process occurs during compression. Dislocations appear during deformation, migrate and accumulate into LABs, and then rotate into HABs to form new grain.The three-dimensional orientation distribution functions (ODFs) in different stress states were measured, with related texture types and distribution laws compared. According to ODFs with a constant φ2, the deformation texture of {011} <100>Goss texture is gradually strengthened during thermal tension at high temperature and low strain rate (450°C/0.001s-1). The deformation texture of {011} <100>Goss texture is weakened with the strain increasing. Furthermore, the increase of deformation temperature or the decrease of strain rate slows down the weakening process of {011} <100> Goss texture, which is attributed to the recrystallization behavior during tensile deformation. Besides, since the recrystallization process proceeds more completely during hot compression, it produces a quasi-random texture.
Hot Deformation Behavior of Al-Cu-Li-Mg-Zn-Zr-Sc Alloy in As-Cast and Hot-Rolled Condition
Authors: Erisov Yaroslav , Surudin Sergey , Grechnikov Fedor
Published: April 2018

The results of physical simulation of hot compression of semi-finished products, selected from a cast ingot and hot-rolled plate from aluminum-lithium alloy V-1461, in the temperature range of 400-460°C and strain rates of 1-60 s-1are presented. It is established that at a constant strain rate the flow stresses decrease with increasing test temperature, an increase in the strain rate leads to an increase in flow stresses at a constant temperature. The parameters of the hot deformation rheological model, including the Zener-Hollomon parameter and the hyperbolic sine law, are determined. It is established that the parameters of the rheological model for the cast and hot-rolled state differ insignificantly.
Study on Thickness Distribution and Spring Back Phenomena of Sheet-Bulk Forming for Aluminum Alloy
Authors: Ye Jhan Hong , Hsu Quang Cherng
Published: April 2018

With the advance of technology, aluminum alloy has been widely used in industry. In this study, the formability and spring back phenomena of thick aluminum alloy sheet metal were investigated. Deform-3D and Simufact.forming software were used to simulate the sheet-bulk forming. To find the optimal element size, the convergence analysis method for mesh of simulation process was utilized. In addition, thickness distribution and spring back phenomena of the rectangular blank with round feature of corners were also evaluated. Simulation results were compared to scanning file that obtained via ATOS based on spring back phenomena from experiments. Study results show that the optimal element size is 2 mm. The cross section that is near binder area in x-direction and near quarter area of laptop keyboard in y-direction has minimum spring back. Solid-shell element is better than tetrahedral element for analyzing sheet bulk metal forming process.
Association of trypanosomosis risk with dairy cattle production in western Kenya
Authors: Mugunieri G.L. , Matete G.O.
Published: April 2018

Dairy cattle reared in western Kenya are exposed to medium to high levels of trypanosomosis risk. The social background, farm characteristics and dairy cattle productivity of 90 and 30 randomly selected farmers from medium- and high-risk trypanosomosis areas, respectively, were compared. All the 120 farmers were visited between July and August 2002. Data analysis was performed using descriptive statistics and analysis of variance. The results showed that increased trypanosomosis risk represented by an increase in disease prevalence in cattle of 1% to 20 % decreased the density of dairy cattle by 53 % and increased the calving interval from 14 to 25 months. The increased risk was also associated with a significant increase in cattle mortalities and in a lactation period of 257 to 300 days. It was concluded that removal of the trypanosomosis constraint on dairy production would lead to expansion of dairying since the domestic demand for dairy products is expected to increase.
Assessing fiscal sustainability in Swaziland
Authors: Nxumalo Welcome N. , Hlophe Nomvuyo F.
Published: April 2018

Background: Understanding and assessing fiscal sustainability is essential in ensuring financial and macro-economic stability. Fiscal sustainability has emerged as an important subject for Swaziland given the increasingly volatile government revenues especially those coming through the South African Customs Union (SACU), which threw the country into a severe fiscal crisis between 2010 and 2012, as well as the pressures on increased government spending in the post-fiscal crisis era. Aim: This article primarily focuses on studying whether Swaziland’s fiscal policy remains on a sustainable path or whether corrective measures would be required. Setting: Study focuses on Swaziland, a small open economy that is vulnerable to external shocks. The country also relies heavily on South African Customs Union (SACU) revenues. Methods: The study employs a broad approach to assessing fiscal sustainability in Swaziland covering both deterministic and stochastic analysis. On the deterministic analysis, the article studies the evolution of debt given macro-economic variables and further estimates fiscal sustainability indicators such as the primary gap and tax-gap. From a stochastic analysis, the article uses the Trehan and Walsh Methodology as well as Hakkio and Rush Methodology. Results: Fiscal sustainability indicators reflected that the country is on an unsustainable path with a primary gap and tax-gap of about 7% of gross domestic product (GDP) that has to be corrected. The econometric results also portray an evidence of ‘weak-form’ sustainability in the long-run. This is because public expenditures are rising at a faster pace than revenues thereby rendering government deficits unsustainable in the medium term. The econometric results also suggest a tax-spend hypothesis in the long-run, while short-run developments point to a spend-tax hypothesis. In both instances the correction measure is cutting expenditure, mainly recurrent expenditure. Conclusion: The study recommends corrective measures (mainly cuts in government expenditure) for fiscal policy to be brought back into a sustainable path without which a fiscal crisis is imminent. The recommendations are mainly based on the fiscal sustainability indicators as they are more forward looking for the short to medium term. The article suggests fiscal rules based on these indicators.
Accuracy and Safety of Percutaneous Lumbosacral Pedicle Screw Placement Using Dual-Planar Intraoperative Fluoroscopy
Authors: Dunn Conor , Faloon Michael , Milman Edward , Pourtaheri Sina , Sinah Kumar , Hwang Ki , Emami Arash
Published: April 2018

Study Design

Retrospective case series with prospective arm.

Purpose

To assess the safety and accuracy of percutaneous lumbosacral pedicle screw placement (PLPSP) in the lumbosacral spine using intraoperative dual-planar fluoroscopy (DPF).

Overview of Literature

There are several techniques available for achieving consistent, safe, and accurate results with PLPSP. There is a paucity of literature describing the beneficial operative, economic, and clinical outcomes of DPF, the most readily accessible image guidance system.

Methods

From 2004 to 2014, 451 consecutive patients underwent PLPSP using DPF, for a total of 2,345 screw placement. The results of prospectively obtained postoperative computed tomography (CT) examinations of an additional 41 consecutive patients were compared with the results of 104 CT examinations obtained postoperatively due to clinical symptomatology; these results were interpreted by three reviewers. The rates of revision indicated by misplaced screws with consistent clinical symptomatology were compared between groups. Pedicle screw placement was graded according to 2-mm increments in medial pedicle wall breach and measurement of screw axis placement.

Results

Seven of the 2,345 pedicle screws placed percutaneously with the use of the dual-planar fluoroscopic technique required revision because of a symptomatic misplaced screw, for a screw revision rate of 0.3%. There were no statistically significant demographic differences between patients who had screws revised and those who did not. All screws registered greater than 10 mA on electromyographic stimulation. In the 41 prospectively obtained CT examinations, one out of 141 screws (0.7%) was revised due to pedicle wall breach; whereas among the 104 patients with 352 screws, three screws were revised (0.9%).

Conclusions

DPF is an extremely accurate, safe, and reproducible technique for placement of percutaneous pedicle screws and is a readily available and cost-effective alternative to CT-guided pedicle screw placement techniques. Postoperative CT evaluation is not necessary with PLPSP unless the patient is symptomatic. Acceptable electromyographic thresholds may need to be reevaluated.
Vertebral Lateral Notch as Optimal Entry Point for Lateral Mass Screwing Using Modified Roy-Camille Technique
Authors: Yamamoto Norio , Kosaka Hirofumi , Higashino Kosaku , Morimoto Masatoshi , Yamashita Kazuta , Tezuka Fumitake , Hayashi Fumio , Takata Yoichiro , Sakai Toshinori , Nagamachi Akihiro , Sairyo Koichi
Published: April 2018

Study Design

Retrospective study of 37 consecutive female patients with cervical spondylotic myelopathy who underwent reconstructed computed tomography (CT) scanning of the cervical spine.

Purpose

The purpose of this study was to investigate whether the vertebral lateral notch of the cervical spine is an effective landmark to determine the entry point for lateral mass screwing. A modified Roy-Camille technique was used to determine the entry point associated with the lateral notch of the cervical spine.

Overview of Literature

The Roy-Camille technique has been a popular technique for the posterior fixation of the cervical spine. A problem with this technique is determining the entry point on the lateral mass via visual inspection, such as in cases with degenerative or destructive cervical facet joints.

Methods

Thirty-three female patients with cervical spondylotic myelopathy underwent reconstructed CT scanning of the cervical spine. Overall, 132 vertebrae from C3 to C6 were reviewed using reconstructed CT. The probable trajectory using a modified Roy-Camille technique was determined using reconstructed CT scans, and the optimal entry point was identified. Horizontal and vertical distances from the vertebral lateral notch were measured.

Results

The entry point determined using the modified Roy-Camille technique was significantly superior and medial compared with that determined using the conventional Roy-Camille technique. At C3 and C4 levels, the entry point using the modified technique was 1.4 mm below and 4.4 mm medial to the lateral notch, and at C5 and C6 levels, it was 2.3 mm below and 4.9 mm medial to the lateral notch.

Conclusions

The vertebral lateral notch of the cervical spine was an effective landmark to determine the entry point for lateral mass screwing. The modified Roy-Camille technique proposed here may prevent surgical complications and poor outcomes.
Comparative Prospective Study Reporting Intraoperative Parameters, Pedicle Screw Perforation, and Radiation Exposure in Navigation-Guided versus Non-navigated Fluoroscopy-Assisted Minimal Invasive Transforaminal Lumbar Interbody Fusion
Authors: Dusad Tarun , Kundnani Vishal , Dutta Shumayou , Patel Ankit , Mehta Gaurav , Singh Mahendra
Published: April 2018

Study Design

Prospective cohort study.

Purpose

To compare intraoperative parameters, radiation exposure, and pedicle screw perforation rate in navigation-guided versus non-navigated fluoroscopy-assisted minimal invasive transforaminal lumbar interbody fusion (MIS TLIF).

Overview of Literature

The poor reliability of fluoroscopy-guided instrumentation and growing concerns about radiation exposure have led to the development of navigation-guided instrumentation techniques in MIS TLIF. The literature evaluating the efficacy of navigation-guided MIS TLIF is scant.

Methods

Eighty-seven patients underwent navigation- or fluoroscopy-guided MIS TLIF for symptomatic lumbar/lumbosacral spondylolisthesis. Demographics, intraoperative parameters (surgical time, blood loss), and radiation exposure (sec/mGy/Gy.cm2 noted from C-arm for comparison only) were recorded. Computed tomography was performed in patients in the navigation and non-navigation groups at postoperative 12 months and reviewed by an independent observer to assess the accuracy of screw placement, perforation incidence, location, grade (Mirza), and critical versus non-critical neurological implications.

Results

Twenty-seven patients (male/female, 11/16; L4–L5/L5–S1, 9/18) were operated with navigation-guided MIS TLIF, whereas 60 (male/female, 25/35; L4–L5/L5–S1, 26/34) with conventional fluoroscopy-guided MIS TILF. The use of navigation resulted in reduced fluoroscopy usage (dose area product, 0.47 Gy.cm2 versus 2.93 Gy.cm2), radiation exposure (1.68 mGy versus 10.97 mGy), and fluoroscopy time (46.5 seconds versus 119.08 seconds), with p-values of <0.001. Furthermore, 96.29% (104/108) of pedicle screws in the navigation group were accurately placed (grade 0) (4 breaches, all grade I) compared with 91.67% (220/240) in the non-navigation group (20 breaches, 16 grade I+4 grade II; p=0.114). None of the breaches resulted in a corresponding neurological deficit or required revision.

Conclusions

Navigation guidance in MIS TLIF reduced radiation exposure, but the perforation status was not statistically different than that for the fluoroscopy-based technique. Thus, navigation in nondeformity cases is useful for significantly reducing the radiation exposure, but its ability to reduce pedicle screw perforation in nondeformity cases remains to be proven.
Does Vertical Ground Reaction Force of the Hip, Knee, and Ankle Joints Change in Patients with Adolescent Idiopathic Scoliosis after Spinal Fusion?
Authors: Yusof Mohd Imran , Shaharudin Shazlin , Sivalingarajah Prema
Published: April 2018

Study Design

Comparative cross-sectional study.

Purpose

We measured the vertical ground reaction force (vGRF) of the hip, knee, and ankle joints during normal gait in normal patients, adolescent idiopathic scoliosis (AIS) patients with a Cobb angle <40° and in AIS patients with spinal fusion. We aimed to investigate whether vGRF in the aforementioned joints is altered in these three groups of patients.

Overview of Literature

vGRF of the lower limb joints may be altered in these groups of patients. Although it is known that excessive force in the joints may induce early arthritis, there is limited relevant information in the literatures.

Methods

We measured vGRF of the hip, knee, and ankle joints during heel strike, early stance, mid stance, and toe-off phases in normal subjects (group 1, n=14), AIS patients with Cobb angle <40° (group 2, n=14), and AIS patients with spinal fusion (group 3, n=13) using a gait analysis platform. Fifteen auto-reflective tracking markers were attached to standard anatomical landmarks in both the lower limbs. The captured motion images were used to define the orientations of the body segments and force exerted on the force plate using computer software. Statistical analysis was performed using independent t-test and analysis of variance to examine differences between the right and left sides as well as those among the different subject groups.

Results

The measurements during the four gait phases in all the groups did not show any significant difference (p>0.05). In addition, no significant difference was found in the vGRF measurements of all the joints among the three groups (p>0.05).

Conclusions

A Cobb angle <40° and spinal fusion did not significantly create imbalance or alter vGRF of the lower limb joints in AIS patients.