bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inverse problem and null-controllability for parabolic systems
Authors: García Galina C. , Takahashi Takéo 
Published: August 2011

AbstractIn this paper, we present some abstract results giving a general connection between null-controllability and several inverse problems for a class of parabolic equations. We obtain some conditional stability estimates for the inverse problems consisting of determining the initial condition and the source term, from interior or boundary measurements. We apply this framework for Stokes system with interior and boundary observations, for a coupling of two Stokes system and a linear fluid-structure system.
A generalization of continuous regularized Gauss–Newton method for ill-posed problems
Authors: Nair M. Thamban , Ravishankar P. 
Published: August 2011

Abstract
A generalization of a simplified form of the continuous regularized Gauss–Newton method has been considered for obtaining stable approximate solutions for ill-posed operator equations of the form F(x) = y, where F is a nonlinear operator defined on a subset of a Hilbert space ℋ1 with values in another Hilbert space ℋ2. Convergence of the method for exact data is proved without assuming any specific source condition on the unknown solution. For the case of noisy data, order optimal error estimates based on an a posteriori as well as an a priori stopping rule are derived under a general source condition which includes the classical source conditions such as the Hölder-type and logarithmic type, and certain nonlinearity assumptions on the operator F.
Determination of the unknown time dependent coefficient p(t) in the parabolic equation ut
= Δu + p(t)u + φ(x, t)
Authors: Ou Yunhua , Zhao Jing , Liu Zhenhai , Tang Jiang 
Published: August 2011

Abstract
This paper is devoted to a class of inverse coefficient problems for parabolic differential equations. These problems play a very important role in many branches of engineering and sciences. Based on a variational iteration technique, we show the rapid convergence of the approximated solution sequence constructed to the exact solution. To show the efficiency of the present method, one example is displayed.
Nano- and microcomplexes of biopolymer carrageenans and dodecylammonium chloride
Authors: Vinceković Marko , Bujan Marija , Sikirić Maja Dutour 
Published: August 2011

Abstract
Polymer and surfactant complexation was investigated in systems containing anionic biopolymers and cationic surfactants by various classical and modern methods. Differently charged carrageenans (one, two or three sulfate groups per monomeric unit) and dodecylammonium chloride (DDACl) were used as model systems. Formation of various soluble and insoluble complexes (from nano- to microdimensions) and gelation strongly depends on carrageenan and DDACl concentrations, their molar ratio and linear charge density on carrageenan chains. The main factors governing complexation include electrostatic and hydrophobic interactions as well as conformation of carrageenan chains. With increasing carrageenan concentration, the intramacromolecular complexes change to intermacromolecular, which subsequently reorganize into better ordered structures, giant vesicles, and precipitated stoichiometric compounds, dodecylammonium carrageenates. Structural analysis of the new compounds revealed the formation of a lamellar structure with the polar sublayer containing carrageenan chains and the non-polar sublayer consisting of disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. At gelling carrageenan concentration, progressive addition of DDACl caused gradual transitions from the structure of carrageenan gel alone to lamellar ordering of collapsed gel balanced by intermolecular forces within the gel network, i.e., by hydrogen bonding, electrostatic, hydrophobic and van der Waals forces.
Dynamic mechanical behavior of phenoxy/carbon nanotube composites: assessment through different functionalization
Authors: Disfani Mahdi Najjar , Jafari Seyed-Hassan , Khonakdar Hossin Ali 
Published: August 2011

Abstract
Nanocomposites of phenoxy resin with various functionalized multi-walled carbon nanotubes (CNTs) were investigated to assess and compare the effect of functionalization on dynamic mechanical properties. Non-functionalized and various functionalized CNTs containing -COOH, -OH, and -NH2 groups were utilized for preparing phenoxy/CNT nanocomposites through a melt mixing process. Dynamic mechanical properties of nanocomposites, storage modulus (E′), and loss tangent (tanδ) data in temperature range of 20–120°C were collected. Transmission electron microscopy and optical microscopy were also used to gain an insight into the CNTs dispersion state within phenoxy matrix. The functionalized CNTs had no adverse effect on storage modulus of phenoxy. The morphological investigation revealed the highest degree of agglomeration and the shortest tube lengths for the CNT-COOH within phenoxy matrix.
Thermo-mechanical properties and thermal conductivity of CdS-trans-polyisoprene, polymer nanocomposite
Authors: Baboo Mahesh , Dixit Manasvi , Patidar Dinesh , Sharma Kananbala , Saxena Narendra Sahai 
Published: August 2011

Abstract
This paper focuses on the comparative evaluation of the glass transition temperature (Tg), storage modulus and thermal conductivity of trans-polyisoprene (TPI) and CdS-TPI nanocomposite. The CdS nanoparticles synthesized by chemical route are dispersed into TPI using ultrasonic vibrations. Particle size of nanocrystals is obtained from X-ray diffraction and found to be 1.84 nm. Thermo-mechanical properties (Tg and storage modulus) are measured by dynamic mechanical analyzer (DMA), while thermal conductivity is a measured using the transient plane source (TPS) technique. It is observed that glass transition temperature and thermal conductivity are higher while storage modulus and mechanical properties are lower for CdS-TPI nanocomposites than for pure TPI. This has been explained on the basis of structural changes occurring due to introduction of CdS as filler into the TPI.
Performance of high temperature superconducting ceramic/thermoplastic polymer composites
Authors: Bhadrakumari Sarojini , Predeep Padmanabhan 
Published: August 2011

Abstract
A technique for preparing flexible composites by dispersing high Tc yttrium based superconductor filler in a polyethylene matrix with transition temperature of about 90 K has been developed. Susceptibility measurements demonstrated a high degree of field exclusion, indicating that the superconducting behavior is preserved in the yttrium barium copper oxide (YBa2Cu3O7-×) filler material. It is found that all the composites showed the diamagnetic transition at around 90 K, which is the same as that of the pure YBCO sample. The single transition for both the parent YBCO material and the composite samples indicates the dominant presence of isolated superconducting grains within such samples. A large drop in resistivity with increasing filler content is observed for all the ceramic-polymer systems investigated in this study. At low percentages of the filler, the composite behaves as an insulator with very low conductivity. No dc zero resistance transition is observed. The absence of zero resistance in these composites was presumably due to the absence of appropriate contacts between the superconducting grains and the lack of a conductive path necessary for a zero resistance transition to occur.
Numerical and experimental studies on extrudate swell of branched polyethylene through axisymmetric and planar dies
Authors: Ganvir Vivek , Gautham Basavarsu , Thaokar Rochish , Lele Ashish , Pol Harshwardhan 
Published: August 2011

Abstract
Extrudate swell is simulated using an Arbitrary Lagrangian Eulerian (ALE) technique based finite element formulation and the same has been validated by comparing the results with reported numerical and experimental studies. In the present work we compare our ALE simulations with our own experimental data on the extrudate swell of commercial grade low density polyethylene (LDPE) resin. The resins were characterized for their rheological behavior in both shear and uniaxial extension. The polymers were extruded from a capillary under isothermal conditions and the extrudates were observed on-line using a video camera. ALE simulations were performed using molecular constitutive model like eXtended Pom–Pom (XPP) for branched (LDPE). The simulated extrudate swell was a good match with the experimental data. It was found that the swell values of LPDE through planar die are higher than the axisymmetric die.
Role of important parameters in ring opening polymerization of polylactide
Authors: Kaur Paramjit , Mehta Rajeev , Upadhyay Sidh Nath 
Published: August 2011

Abstract
Different parameters, namely polymerization temperature, polymerization time, monomer/initiator ratio, nature of the initiator, amount of water or other impurities etc. are very significant for polymerization reactions either in bulk or solution. Monomer to initiator ratio has a very significant role in polymerization reactions and a value ranging from 50 to 5000 that has been reported by different researchers. Recrystallization of the monomer removes the meso compounds from the monomer, which absorbs the moisture and effects polymerization reaction. So, it is necessary to recrystallize the monomer with any anhydrous solvent like dry toluene, ethyl acetate etc. Prolonged reaction time cannot increase the polymer yield; it generally causes the decrease of molecular weight and broadening of molecular weight distribution of formed polymers. This is probably due to the transesterification side reaction in polymerization, intensifying at prolonged time periods. Several groups like hydroxyl and carboxylic acid affect the polymerization rate.
Aromatic polyurethanes: the effect of hard segment and chain structure on their properties
Authors: Mishra Abhinay , Maiti Pralay 
Published: August 2011

Abstract
Structural variation and its effect on the properties of aromatic polyurethanes (PUs) with different chain structures have been reported. Polarized optical microscopic studies of aromatic PUs demonstrate the development of micro clusters with increasing hard segment content (HSC). Higher crystallinity has also been proven from differential scanning calorimeter (DSC) and X-ray diffraction (XRD) studies. A globular pattern has been observed through atomic force microscopy (AFM) and the pattern depends on the type of diisocyanate used to prepare the PU. The difference in surface morphology is evident for two different PUs. The tensile modulus increases systematically with increasing HSC while toughness decreases, due to the presence of bigger crystallites in higher HSC polymer. Both the modulus and toughness vary on the type of diisocyanate present in PUs.
Development of integrated bioenergy devices for the improvement in the quality of life of poor people
Authors: Omer Abdeen 
Published: August 2011

Abstract
Sudan enjoys abundant solar, wind, hydro, and biomass resources. Like many tropical countries, Sudan has ample biomass resources that can be efficiently exploited in a manner that is both profitable and sustainable. Fuel-wood farming offers cost-effective and environmentally friendly energy solutions for Sudan, with the added benefit of providing sustainable livelihoods in rural areas. Biogas from biomass appears to have potential as an alternative energy in Sudan, which is potentially rich in biomass resources. This is an overview of some salient points and perspectives of biomass technology in Sudan. The current literature is reviewed regarding the ecological, social, cultural and economic impacts of biomass technology. This article provides an overview of biomass energy activities and highlights future plans concerning optimum technical and economical utilization of biomass energy available in Sudan.
Study of mechanical behavior of Kevlar/polypropylene hybrid yarns and their composites
Authors: Sardar Jagannath 
Published: August 2011

Abstract
In this paper, the mechanical characteristics of Kevlar multi-filament-polypropylene (KV M/F-PP) hybrid yarns and its composites have been studied. The hybrid yarns have been prepared by the principle of friction spun method in a DREF-3 (Dr Ernst Fehrer A.G. the name of the inventor 1973) Machine. The system uses Kevlar-29 (poly paraphenylene terephthalamide) multifilament (KV M/F) and polypropylene (PP) of 38 mm staple length fibres as core and sheath materials, respectively. The tensile properties of selected reinforcing materials and hybrid yarns are tested before preparing the composite samples. The weight percentages of KV M/F were kept as 0%, 15%, 20%, 25% and 30% corresponding to the percentages of matrix. DREF-3 hybrid yarns are characterized by very homogeneous component distributed over the yarn cross-section. The hybrid yarn is used for thermoplastic composites in compression molding, where Kevlar multifilaments take place in core as reinforcing materials and sheath or wrapped PP fibres as matrix. The prepared composite samples have been studied using specific standards to evaluate the void volume fraction and the tensile behavior in the standard conditions. The composite having 30% of Kevlar shows the highest tensile strength with a high void percentage, however, the elongation to break is a minimum due to lower weight percentage of low elastic modulus polypropylene matrix as compare to other samples.
Water transport, FTIR, and morphology characterizations of novel biodegradable blends based on poly(3-hydroxybutyrate)
Authors: Shchegolikhin Alexander N. , Iordanskii Alexey L. , Filatova Anna , Gumargalieva Klara Z. , Fomin Sergey V. , Potapov Evgeniy E. 
Published: August 2011

Abstract
This paper focuses on the study of novel blends based on poly(3-hydroxybutyrate) (PHB) and polymers with different hydrophilicity [polyethylene (PELD) and polyamide resin (PA548)]. Polymer blends were produced from five ratios of PHB/PELD in an effort to regulate the resistance to hydrolysis or (bio)degradation through the control of water permeability. The relation between the water transport and morphology (TEM data) shows the impact of polymer component ratio on the regulating water flux in hydrophobic matrix. To elucidate the role of hydrophilicity of the second component in the PHB blends, we studied the PHB/PA blends where PA is the polyamide resin composed of statistical copolymer of hexamethyleneadipinate and ε-caprolactam in ratio 1:1. The complex of techniques including DCS and Fourier Transform Infrared (FTIR)-imaging (on the scale of temperature) indicates an interaction between PHB and PA in the temperature ranges of crystallization and melting. The general approach based on Flory-Huggins equation is presented as a way to choose pairs of compatible or partly compatible polymers. Blending PHB with PA could be a simple and effective method to design new matrices for drug delivery, while the same procedure applied to PHB-PELD system with better resistance again, hydrolysis and lower cost than parental PHB could be used as novel bioerodible packaging materials.
Structural investigation of conducting polythiophene composites
Authors: Shirbhate Nitin V. , Yawale Shrikrishna P. , Tambakhe Smita V. , Bobade Rajeshwar S. , Pakade (Yawale) Sangita V. 
Published: August 2011

Abstract
Polythiophene (PTh) – polyvinyl acetate (PVAc) composite films were prepared by chemical oxidative polymerization with ZnCl2 as oxidant, in methanol solvent at room temperature. In this study DC conductivity as a function of temperature was measured. An attempt has been made to investigate the effect of temperature and concentration of ZnCl2 oxidant on the conductivity of polythiophene and polyvinyl acetate composite films. For fixed wt% of PVAc, the DC electrical conductivity initially increases with the molar concentration of ZnCl2 which increases the rate of polymerization and then decreases with further increase in concentration of ZnCl2 due to reduced segmental motion of the polymer. The Fourier transforms infrared (FTIR) spectra reveal that the structure remains the same throughout the series. The small shift in the observed peak frequencies is due to composition change of ZnCl2, but the overall trend of the IR spectra is the same. From the finger print region it is observed that the terminal branching is completely absent. The ionic transference number is calculated from the polarization current versus time plot. Ionic contribution is found to be dominant. The thermo gravimetry (TG) curves of the samples show single step degradation.
Assessments by HR and %HRR of Occupational Work Exertion for Alternating Periods of Rest and Manual Labor
Authors: Eguchi Yasumasa , Kawanami Shoko , Horie Seichi , Yamato Hiroshi 
Published: August 2011

Assessments by HR and %HRR of Occupational Work Exertion for Alternating Periods of Rest and Manual Labor: Yasumasa Eguchi, et al. Department of Health Development, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan—ObjectivesMetabolic equivalents (METs) and relative metabolic rate (RMR) as calculated by oxygen uptake () are often used to assess physical exertion. In practice, accurate measurements of are dificult; heart rate (HR) values represent an alternate index of physical exertion. We investigated whether one can assess physical exertion based on HR in the workplace, even if the physical task in question involves alternating periods of strenuous anaerobic activity and rest. We also examined the potential usefulness of assessments based on percentage of heart rate reserve (%HRR) and percentage of oxygen uptake reserve (% ).MethodsSix healthy men were asked to perform several physical movements. HR and were recorded in real time.ResultsHR and are significantly correlated even under conditions of various repeated intermittent movements including anaerobic exertion. Cumulative fatigue results in inadequate recovery in various parameters indicating suficient rest times, whereas values recover immediately. One movement may generate large differences in HR among individuals, but not in . We found no significant differences between dispersion for %HRR and . However, as with HR, %HRR values indicated insuficient recovery after strenuous exertion.Conclusions alone does not adequately reflect the exertion entailed by certain physical activities. HR is more useful than in evaluating the exertion required by physical labor in individual workers. While we can use %HRR and % to compare physical exertion from individual to individual, %HRR is more valuable, since % can underestimate physical exertion in recovery periods for the same reasons as .
Safety and Health in the Petrochemical Industry in Map Ta Phut, Thailand
Authors: Langkulsen Uma , Vichit‐Vadakan Nuntavarn , Taptagaporn Sasitorn 
Published: August 2011

Safety and Health in the Petrochemical Industry in Map Ta Phut, Thailand: Uma Langkulsen, et al. Faculty of Public Health, Thammasat University, Rangsit Campus, Thailand—BackgroundPetrochemical industries are known as sources of many toxic chemicals. Safety and health risks of the petrochemical workers employed at Map Ta Phut Industrial Estate, located in Rayong, Thailand, are potentially high.MethodsThe research materials consisted of documents emanating from statutory reports on safety in working with toxic chemicals and the results of interviews by questionnaire among 457 petrochemical workers regarding occupational health and safety issues.ResultsMost of workers who were working with toxic chemicals had knowledge and awareness of health risks and chemical hazards at work. We found that safe behavior at work through read the safety information among operational workers less than non‐operational workers around 10%. Most of workers had perceived occupational health and safety management in their companies. Some companies revealed that they had not been performing biological monitoring of blood or urine for their health examination reports and that workplace exposure monitoring had not correlated well with health examination of workers.ConclusionsOur study suggested that occupational health and safety for petrochemical industries requires standards and guidelines for workers' health surveillance aimed at protection of workers.
Association Between Type 2 Diabetes and Exposure to Persistent Organic Pollutants
Authors: Airaksinen Riikka , Rantakokko Panu , Eriksson Johan G. , Blomstedt Paul , Kajantie Eero , Kiviranta Hannu 
Published: August 2011

OBJECTIVE
The prevalence of type 2 diabetes is increasing alarmingly in both developed and developing countries. Recently, exposure to persistent organic pollutants (POPs) has been associated with the prevalence of type 2 diabetes. The purpose of this cross-sectional study is to examine the association between type 2 diabetes and POP exposure in the Helsinki Birth Cohort Study.

RESEARCH DESIGN AND METHODS
The cohort consists of 8,760 people born in Helsinki during 1934–1944, before the global POP emission peak. In 2003, a clinical examination was performed, including blood sampling for laboratory analyses of serum lipids and POPs. Complete data from the examination were available for 1,988 participants. The concentrations of each POP were categorized into four groups on the basis of percentile intervals, and logistic regression was performed to examine diabetes prevalence across the POP categories, adjusting for sex, age, waist circumference, and mean arterial pressure and using the lowest category as the reference group.

RESULTS
Among the participants with the highest exposure to oxychlordane, trans-nonachlor, 1,1-dichloro-2,2-bis-(p-chlorophenyl)-ethylene (p,p’-DDE, and polychlorinated biphenyl 153, the risk of type 2 diabetes was 1.64–2.24 times higher than that among individuals with the lowest exposure (Plin = 0.003–0.050, where Plin is the P value for linear trend across POP categories). In the stratified analysis, the associations between type 2 diabetes and oxychlordane and trans-nonachlor remained significant and were strongest among the overweight participants. Exposure to 2,2′,4,4′-tetrabromodiphenyl ether (BDE 47) and 2,2′,4,4′,5,5′-hexabromodiphenyl ether (BDE 153) was not associated with type 2 diabetes.

CONCLUSIONS
This study confirms the association between type 2 diabetes and adult-only exposure to organochlorine pesticides in a general urban population.