bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of the Temperature, Stress, Strain Field in Aluminum Thin-Gauge High-Speed Casting
Authors: Liu Xiao Bo , Wu Dun Sheng
Published: December 2011

Based on the analyses of aluminum melt solidification and heat transfer during the process of twin-roll casting, a coupling mathematical model of thin-gauge high-speed casting was developed, which included the casting roller shell. At the same time, FEM was adopted to solve the coupling model. The temperature field, thermal stress field and strain field of aluminum melt in casting zone were simulated by this model. When the casting velocity is 7m/min, and the thickness of strip is 2 mm, in the melt zone, the temperature of melt decreases rapidly as it approaches the rollers; the surface stress of strip is larger than the central stress; In the liquid zone and mushy zone, thermal stress is relatively small; in rolling zone, thermal stress is much larger than in the former two zones, and gradually increases along exports, then gradually decreases after the peak; the outsurface strain of the casting strip is larger than the inner strain, and the thermal stress gradually increases along exports.
Effect of Additive on Microwave Absorption Properties of Hollow Ceramic Microspheres Prepared by Self-Propagating High-Temperature Synthesis (SHS) Flame Quenching Technology
Authors: Lou Hong Fei , Wang Jian Jiang , Huang Hong Jun , Hu Wen Bin , Huo Xing Jian
Published: December 2011

In order to improve microwave absorption properties of hollow ceramic microspheres (HCMs) and possess the better characteristics of “thinness、width、lightness、strongness”, used Al+Cr2O3 as the main reaction system, hollow ceramic microspheres were prepared by SHS flame quenching technology. Microwave absorption properties of HCMs were studied when the additive is Fe. The results show that microwave absorption properties of HCMs depend on the dielectric property of product, such as SiC、mullite, when there is no additive. However, when Fe is used as additive, the microwave absorption properties of HCMs are better. SHS reaction of agglomerate powders is happened in the flame field and SiC、Fe2O3、Al3Fe5O12、Cr1.3Fe0.7O3、(Fe0.6Cr0.4)2O3 are synthesized. Except the dielectric property of SiC, magnetic property of HCMs is possessed due to the ferruginous materials are synthesized. So its microwave absorption properties are stronger. Keywords: additive; hollow ceramic microspheres; microwave absorption properties
Total Fatigue Life Prediction under Constant Amplitude Loading
Authors: He Yu Ting , Shu Wen Jun , Cui Rong Hong , Wu Li Ming , Du Jin Qiang
Published: December 2011

This paper applies the fracture-mechanics-based analysis and the crack-closure concept to naturally occurring small cracks and large crack growth, and to make total fatigue life predictions solely based on crack growth from the assumed initial materials defect. The equation of total fatigue crack propagation life under constant amplitude loading is presented. And the total fatigue propagation lives of LY12-BCZYU aluminium alloy SENT specimens by this equation and validated by experimental results. Validation against calculations by the model and experimental data shows a good agreement.
Numerical Simulation of Fracture Saturation in Multilayer Materials in Symmetric Case
Authors: Han Feg Shan
Published: December 2011

Using Realistic Failure Process Analysis Code RFPA2D, a three layer materials model with a central layer and with the same thickness top and bottom layer, progressive formation of fracture saturation in multilayer materials is simulated in all case by numerical simulation. Our numerical simulation recurrence the phenomenon of fracture saturation in multilayer materials. numerical simulation shown that for the symmetric case the spacing of these fractures at fracture saturation are approximately the same and lineally related to thickness of the fractured layer. We investigate that the critical fracture spacing to layer thickness ratio is function of the thickness ratio of the top and bottom layers to central layer at fracture saturation. numerical simulation shown that for the symmetric case the critical spacing of fractures to layer thickness ratio decreases rapidly and tends to a constant value.
Influence of Three-Step Aging Heat Treatment on Properties of 7A04 Aluminum Alloy
Authors: Li Qiu Ze , Xu Lei , Song Ji Xiao , Han Jing , Huang Xing Min , Dai Guang Ze
Published: December 2011

Aiming at traditional peak aging of 7A04 Aluminum Alloy with high strength but low corrosion resistance, innovative gradually cooling three-step aging heat treatment process were designed, conventional mechanical properties and corrosion resistance of 7A04 aluminum after three kinds of aging treatments was studied through microstructure. The results show that compared with the traditional peak aging process, two gradually cooling three-step aging process is to improve materials tensile strength, plastic and impact toughness in different degrees. Meanwhile corrosion resistance of materials has improved significantly. And extension of low temperature aging time is conducive to the further improvement of strength.
Effect of Marangoni Convection on Welding Pool of Plasma Direct Metal Forming Finite Element Model
Authors: Xia Dan , Xu Bin Shi , Lv Yao Hui , Jiang Yi , Liu Cun Long
Published: December 2011

With considering the Marangoni convection in the molten pool on plasma direct metal forming process, a finite element model posed to describe and reflect the flow in the molten pool. Results of temperature distribution modeling prepared by plasma direct metal forming process of metal powders in an Ar environment were numerically obtained and compared with experimental data. Powders of Fe314 and base plates of R235 steel were taken as sample materials. In the experiment a multi-stream nozzle capable of delivering metal powder coaxially with the plasma arc was used. The model revealed that the velosity of the front part of the pool is a little slower than aft part. Marangoni convection reinforced the convection and enhanced the heat transfer. Profile of the model is the same as the experimental data. This allows us to conclude that the model can be applied for preselecting the process parameters. Keywords: plasma, rapid forming, temperature field, Marangoni convection.
Numerical Simulation of Molten Metal Droplet Impinging in Uniform Droplet Spray Rapid Prototyping
Authors: Yin Feng Liang , Zhu Sheng , Liu Jian , Liang Yuan Yuan
Published: December 2011

A two-dimensional mathematical model has been developed to simulate the impinging and solidification process of a single droplet onto substrate in uniform droplet spray rapid prototyping. Droplet free surface is tracked by volume-of-fluid (VOF) algorithm. The effect of surface tension on the droplet is taken into consideration by means of considering surface tension to be a component of the body force. The governing equations are solved using a finite volume formulation. The calculation results predicted the final shape of a molten droplet impacting onto a solid substrate, and revealed that the solidification process began at the leading edge with the spread process of droplet. The simulation results provide insight and information not easy available from experimental. Keywords: numerical simulation, droplet, rapid prototyping
The Morphology and Evolution of Cu6Sn5 at the Interface of Sn-2.5Ag-0.7Cu-0.1RE/Cu Solder Joint during the Isothermal Aging
Authors: Wang Yao Li , Zhang Ke Ke , Li Chen Yang , Han Li Juan
Published: December 2011

The morphology and growing behavior of Cu6Sn5intermetallic compound (IMC) of low Ag content Sn-2.5Ag-0.7Cu-0.1RE/Cu solder joint interface are investigated by adopting the X-ray diffraction, JSM-5610LV scanning electronic microscope and energy spectrum analysis. The results show that the cross-section morphology Cu6Sn5of the solder joint interface is scallop-like and its section morphology is circle-like grain. With the aging time increasing, the cross-section Cu6Sn5morphology of the solder joint interface can be changed from the scallop-like to the shape-layer, and the growing kinetics is coincidence with the law of parabola and its growing behavior is controlled by diffusion. With adding a small amount of rare earth elements in the Sn-2.5Ag-0.7Cu solder alloy, the growing rate of the Cu6Sn5can be reduced.
Study of Carbonitride Precipitates in the Fe-Cr-Mn-N Hardfacing Alloy
Authors: Yang Ke , Xie Xiang , Zhou Rui , Bao Ye Feng , Jiang Yong Feng
Published: December 2011

The Fe-Cr-Mn-N hardfacing alloy was deposited on a low carbon steel substrate by the weld hardfacing technique. Ti and Nb as the most effective nitrogen-fixing elements were added in the hardfacing alloy. Carbonitride precipitates were systematically studied by canning electron microscopy and electron probe microanalyser. The thermodynamics and the effect on the matrix of the formation of carbonitride were also discussed. It was found that carbonitride precipitates were complex carbonitride of Ti and Nb distributing on grain boundary and matrix of the hardfacing alloy. In as-welded condition, primary carbonitride particles were readily precipitated from the hardfacing alloy with large size and morphology as they were formed already during solidification. In heat-treated condition, a large number of secondary carbonitrides can precipitate-out with very fine size and make a great secondary hardening effect on the matrix. As a result, precipitation of carbonitride in the hardfacing alloy can prevent the formation of chromium-rich phase on grain boundaries and increase the wear resistance of the hardfacing alloy. Keywords: carbonitride precipitate, hardfacing alloy, deposit, thermodynamics
Study on the Failure Mechanism of Enamel Coatings in HAZ
Authors: Tao Han , Yong Wang , Liu Wei
Published: December 2011

Because the enamel coatings has excellent ageing resistance and anti-corrosion performance, the service life of pipeline with enamel coatings as protective layer can be increased remarkably comparing with the ones with organic coatings. But when the pipeline is welded, the high temperature of welding arc will do harm to the bonding strength of the enamel coating and the base metal because of the differences of thermo-physical properties between them. In order to study the failure mechanism of enamel coating in the heat affected zone, the stress changing process of enamel/steel was studied through numerical simulation and the interface of enamel/steel was studied by welding thermal simulation technology. The results show that the weakness parts of the welded joints are the imperfect normalized zone and overheated zone. In the imperfect normalized zone, the micro-cracks generate at the interface of enamel/steel because high stress occurred and some coatings fused incompletely because of short staying time at high temperature that induced micro-cracks in the enamel coating under high welding stress, so it was one of the dangerous zones of HAZ. Because high tensile stress formed during cooling that was dangerous to the brittle enamel coating, the bond layer of enamel/steel was damaged by high temperature of welding and the pores generated at the interface of enamel/steel, the coatings of overheated zone could be pulled off from the base metal easily that caused the steel exposed to the corrosion medium directly without the protection of enamel coating, so it was another dangerous zone of HAZ. Keywords: enamel coating; numerical simulation; welding thermal simulation; failure mechanism; HAZ
Solidification Simulation of Melt-Cast Explosive under Pressurization
Authors: Wang Dong Lei , Xie Zhi Yi , Sun Wen Xu , Huang Yong
Published: December 2011

The flow field, temperature field and stress field on the melt-cast explosive process have been studied by using software of Procast combined with experimental method，from which the thermodynamic characteristics of the explosives melt-casting process has been researched. The simulation results show that the charge shrinkage, cracks and pore formation could be effectively reduced by adjusting the temperature and pressure. The simulation results could be used for the optimization of casting processes, thereby improved the safety performance of Melt-cast explosive. Keywords: explosive; casting; simulation; shrinkage defects; cracks;
Numerical Simulation of Weld Metal by Ultra-Narrow Gap Arc Welding
Authors: Zhao Li , Dai Ke Jie , Zhang Fu Ju
Published: December 2011

The ultra narrow gap welding process is suitable to the thick plate, ultra-thick plate welding with the characteristic of highly effective, high quality, low cost, low energy consumption and so on, and is easy to realize the mechanization and the automation. In this paper, the numerical simulation and technical experiment are used to study the form, grow and distribution regulation of the welding temperature field, stress field in welding joint with UNG MAW. Using the calculation to the thickness of 32mm, an example to simulate the magnitude and distribution of the residual stress in welding joint is given. Research shows that it is an effective analysis method to heat process and mechanic behavior in the welding by using finite element method numerical simulation and few experiments. Keywords: UNG MAW, Welding residual stress, Finite element method, Numerical simulation
Study on Fast-Convert Ultrasonic Frequency Pulse TIG Welding Arc Characteristic
Authors: Qi Bo Jin , Yang Ming Xuan , Cong Bao Qiang , Li Wei
Published: December 2011

Based on ultrasonic frequency pulse tungsten inert-gas (TIG) welding for 0Cr18Ni9Ti austenitic stainless steel, the influence of pulse level parameters was investigated on the field of arc characteristic and arc force. The experimental results show that the pulse level parameters could have huge impact to arc characteristic and arc force. With the increased frequency of pulse level, arc plasma has a more obvious pinch effect, which causes the enhance of arc voltage. Similarly, the arc force can be improved obviously compared with that during conventional direct current (DC) TIG welding. By contrast, the sensitivity of welding characteristic to pulse current level frequency would reduce while the duty of pulse peak current increased.
Low-Cycle Fatigue Behavior of Large-Size Dissimilar Steel Welded Tube-Plate Structure
Authors: Xue Gang , Wang Ren Fu , Deng Wang Ping , Fang Hong Yuan , Yang Jian Guo
Published: December 2011

Based on the FEM analysis of the distributions and varieties of the stresses and the strains of the large-size dissimilar steel welded tube-plate structure under cyclic loading, the fatigue crack initiation sites of this structure were predicted. The low-cycle fatigue test was performed to verify the prediction and to study the cracks propagating paths as well. The results indicated that the weld toes linked to the two surfaces of the plate were the positions with the peak values of the maximum stress and the stress amplitude. The plastic deformations in the first loading cycle introduced the tensile-compressive repeated stress cycle at the weld toes during the subsequent loading cycles. It induced the fatigue cracks initiating at the weld toes linked to the two surfaces of the plate respectively. After initiating from the surfaces the cracks propagated along the fusion lines with a short distance then turn into the base metal in the sections vertical to the surfaces. The depth of the crack initiating from the compressed surface was shorter than the one from the tensioned surface.
Numerical Study on Bubble-Melt Two-Phase Flows in the Production Process of Aluminum Foams
Authors: Liu Hong , Xie Mao Zhao , Shi Jun Rui , Liu Hong Sheng
Published: December 2011

Aluminum foams, as a representative of metallic foams, are a kind of very useful and promising functional materials. This paper reports progress in three-dimensional numerical simulations of gas bubble-metallic melt turbulent flows during the foaming process of aluminum foams, in which air is injected into molten aluminum composites and the melt is mechanical stirred by a pitched-blade impeller with an inclined shaft. The bubble-melt two phase flow in the tank is described with an Eulerian-Eulerian two fluid model, the impeller flow region is simulated based on the Multiple Reference Frames (MRF) method. Influences of gas flow rate, impeller rotation speed and initial bubble diameter on the characteristics of the liquid flow field and gas fraction distribution are examined. Computational results show that bubbles tend to accumulate behind the impeller blades and have an approximately uniform distribution near the top surface of the liquid. Gas holdup values are increased with increasing the impeller speed and gas flow rate and decreased with the bubble diameter.
Study on Fracture Micro-Mechanics Mechanism and Dynamic Energy Absorption Property of Closed-Cell Foam Metals
Authors: Lv Xiang Feng , Pan Yi Shan , Xiao Xiao Chun
Published: December 2011

In order to gain a deep understanding of energy absorption property and failure mechanism of closed-cell foam metals, the dynamic energy absorption property of closed-cell foam metals with matrix Al, matrix Al-Si6, matrix Al-Si12 CCAF, Mg matrix, aluminum-fiber and RE-Al alloys are discussed based on the compression and energy absorption test. The influence of different basis materials on absorption property of closed-cell foam metals is discussed, too. It also shows the micro topography of CCAF during the compression process. In addition, micro-mechanics failure mechanism of CCAF is discussed. Results obtained in this research include: (1) the compression deformation curves of different foam metals indicate that matrix Al CCAF is better for energy absorption materials, because of the best energy absorption property and the high strength. (2) the strength of metal foams with matrix Al-Si6, matrix Al-Si12 and matrix Mg are higher than that of matrix Al CCAF, and also have better energy absorption property. However, the failure characteristics of brittle fracture indicate obvious in matrix Al-Si6, matrix Al-Si12 and matrix Mg. (3) the micro-topography of CCAF with matrix Al is simple and uniform. Also the fracture has obvious tear trace. Aluminum-fiber and RE-Al alloys have better compression property, but lower strength and no strength increasing stage lead to destroy suddenly. (4) the curves of energy absorption for matrix Al and matrix Al-Si6CCAF are on the rise. And the maximum of energy absorption is about 2.1MJ/m3. (5) micropore and crack of closed-cell foam metals provide a good space for the compression and energy absorption. Meanwhile, it is the main failure parts of damage. Keywords: closed-cell foam metal; dynamic energy absorption; micro-topography; micro-mechanics
Research on Thermal Mechanical Properties of Rubber Like Materials Based on Numerical Simulation
Authors: Sang Jian Bin , Yu Wen Ying , Liu Bo , Li Xiao Lei , Liu Tie Feng
Published: December 2011

This paper start with a discussion on various types of strain energy functions of rubber like materials. Theoretical analysis based on the strain energy function given in by Y.C.Gao in 1997 is proposed. The material parameters of strain energy function were curve-fitted from the uniaxial tensile test. The selected constitutive relation of rubber like materials was implemented into a finite element code MSC.Marc as a user material subroutine to analyze the thermal and mechanical behavior of rubber seal under the plane strain conditions. Contact force and distribution of the contact stress between lip seal and shaft are analyzed and coupled thermal mechanical analysis of rubber seal was proposed. The contact pressure distribution is readily obtainable from the nonlinear finite element analysis and the coupled thermal mechanical analyses results indicate that the thermal stress only have minor influence on the deformed shape of rubber seal, which will be a useful technique for predicting the properties of rubber seal and providing reference for engineering design. Keywords:rubber like materials, nonlinear finite element, contact analysis, thermal mechanical analysis
Effect of Materials Characteristics on Average Crack Spacing of Reinforced Concrete Specimen
Authors: Zhang Juan Xia , Guo Xian Zhang , Liang Zheng Zhao , Zhang Ya Fang
Published: December 2011

The goal of the present work is to investigate the influence of concrete on failure mode and stress distribution of the reinforced concrete specimens under axial tension by using a numerical test code named Realistic Failure Process Analysis. It can be found that, the periodically distributed fracture spacing phenomenon and tension stiffening phenomenon exist in the failure process of the reinforced concrete structure. Besides, the effect of concrete characteristics on the mechanical behavior and crack spacing of reinforced concrete was also studied in three samples with different concrete strength. The concrete strength value is considered to be an important factor not only to significantly influence the average crack spacing but also to influence the initial peak load of the specimen. In addition, the average fracture spacing is increased and the initial peak load is also increase with the increasing of the concrete strength value, but the mechanical capacities of the concrete has little influence on the ultimate load capacities of the specimen. Keywords: Numerical test; reinforcement concrete, crack distribution, 3D
Effect of Microstructure on Transmission Properties of Polycrystalline Transparent Ceramics
Authors: Li Qing , Zhang Guo Ping , Liu Yang , Wang Hao , Lei Li Wen
Published: December 2011

The transmission properties of polycrystalline transparent ceramics are influenced by the chemical composition and the microstructure of the material. The fundamental optical mechanism of transparent ceramics and the influencing factors on transmission properties were discussed in this paper. The Mie theory for light scattering is applied to calculate scattering coefficients of residual pores and optical birefringence. The in-line transmission curves of the transparent alumina were calculated as a function of pore size, porosity and grain size. The results show that scattering by the residual pores is the dominant influencing factors on transmission properties. The scattering by the residual pores increases with an increase in porosity and the maximum of the scattering was observed when the pore size close to the optical wavelength. Optical birefringence in the transparent ceramics with non-cubic crystal structure has an important effect on the in-line transmission. The in-line transmission increases with a decrease in grain size. Keywords: transparent ceramics; microstructure; light scattering; birefringence
Influence of Hot Extrusion on Microstructure and Mechanical Properties of As-Cast AZ91 Magnesium Alloy
Authors: Zhang Bao Hong , Zhang Zhi Min
Published: December 2011

In order to study the effect of plastic deformation on microstructure and mechanical properties of as-cast AZ91 magnesium alloy, experiments of hot direct extrusion were performed at different extrusion temperatures and different extrusion ratios. The microstructure and mechanical properties of extruded billets and extrudate were measured. Experimental results show that the grain size of as-cast AZ91 magnesium alloy can be dramatically refined by extrusion. Hot extrusion can obviously improve the mechanical properties of as-cast AZ91 magnesium Alloy, comparing with the pre-extruded billet, the tensile strength, yield strength and elongation of extrudate can be improved by at least 69%, 117% and 150% respectively. As the extrusion temperature increases, the tensile strength and yield strength of extrudate will increase. As the extrusion ratio increases, the tensile strength and yield strength of extrudate will increase at first and then fall. At the time of extrusion temperature of 420°C and extrusion ratio of 45, the highest tensile strength of 381Mpa and yield strength of 303MPa can be achieved for the extrudate.
Oxygen Physisorption Characteristics of Coal
Authors: Zhong Xiao Xing , Wang De Ming , Lu Wei , Xin Hai Hui
Published: December 2011

In different conditions (time, temperature and coal particle size), oxygen physisorption of different coal samples were tested by a oxygen adsorption detection instrument with chromatograph, followed by the analysis of the relation between oxygen physisorption in coal self-heating and the propensity of coal to spontaneous combustion. The results indicate that the physisorption reaches 80% of the saturate amount in several seconds, and then with the rapid decline of the sorption rate takes about 1 min to get saturated. The physisorption decreases with the temperature rise, and increases then drops with decreasing coal particle size, only playing a role in oxygen transportation, physisorption heat generation and the first motivation for coal to self-ignite. The content of oxygen physisorption cannot reflect the capacity of chemisorption and chemical reaction during spontaneous combustion. It is concluded that the sole oxygen physisorption cannot identify the oxidation reactivity of coal effectively.
Flow Behavior of Fe-3%Si Steel at High Temperatures and Strain Rates
Authors: An Feng Hui , Sha Yu Hui , Zuo Liang
Published: December 2011

Hot deformation behavior of Fe-3%Si steel within temperature range of 1073~1473K and strain rate range of 0.01~5s−1was investigated by isothermal compression test using thermo-simulation method. Over the applied deformation conditions, steady state flow behavior was well described by the power law relationship with dislocation climb as the rate-controlling mechanism, and the high apparent activation energy can be attributed to the high yield stress. A modified Bergström model was proposed by introducing yield stress, and consequently the whole stress-strain curves can be accurately predicted.
The Indentation Behavior of Closed-Cell Al Foam under the Flat-End Cylindrical Indenter
Authors: Wang Xin Zhu , Zhou Guang Tao
Published: December 2011

The indentation response of the closed-cell Al foam under the flat-end cylindrical indenter is examined by use the finite element method. The MSC/Marc finite element package is used to model the indentation response of the foam panels, and the Al foam was defined in MSC/Marc as the homogeneous, elasto-plastic material. The simulation result reveals that the deformation was found to be almost totally restricted to a spherical cap-shape compacted zone under the indenter, and the shape of the deformation zone is similar to the observed phenomenon from the indentation test.
Interfacial Friction of Ceramics at High Temperature Ring-Compression Test
Authors: Wang Hui Gai , Song Yan Pei , Wang Fei , Zhang Kai Feng
Published: December 2011

Using ring compression tests, the interfacial friction and flow stress of 3Y-TZP/Al2O3 composite at elevated temperatures were investigated. Theoretical calibration curves of the friction factor and the relative average pressure curves for the ring compression tests of 6:3:2 standard rings were drawn based on a velocity field capable of describing the bulge phenomena. The lubricant was the boron nitride (hexagonal). The tests were adopted at temperature range of 1400°C-1600°C. Results indicate that the interfacial friction factor has the value in the range of 0.34-0.49, so that boron nitride lubricant can be used effectively in present temperatures. As two extremely important parameters, the temperature and strain rate have no significant effect on the fraction factor. It is proved reliable that the ring-compression test at 1400°C and even higher is used to evaluate the performance of boron nitride lubricant.
Transmission Electron Microscopy Observations on the Precipitates in Al-Zn-Mg Based Sacrificial Anode Alloy
Authors: Ma Jing Ling , Wen Jiu Ba , Li Quan An , Li Jun Feng
Published: December 2011

nanoscale precipitates in the Al-Zn-In-Mg-Ti-Mn alloy were investigated by regular and high resolution transmission electron microscopy (TEM and HRTEM) and by selective area electron diffraction (SAED). The cast alloy contains the hexagonal structure MgZn2 and the orthorhombic structure Al6Mn precipitates, but after aged the precipitates of the cubic structure Mg2Zn11 were found. The Mg2Zn11 precipitates can act as activation centre, make the alloy pitting. But the activation of Al6Mn precipitates is very little.
Bosentan and Sildenafil in the Treatment of HIV-Associated Pulmonary Hypertension
Authors: Chinello Pierangelo , Cicalini Stefania , Cortese Andrea , Cicini Maria Paola , Petrosillo Nicola
Published: December 2011

We present the case of an HIV/HCV-coinfected patient with HIV-related pulmonary hypertension (HRPH) who experienced a good clinical and functional response to bosentan, with a subsequent switch to oral sildenafil due to increased transaminase levels. Bosentan resulted less handy in this case, probably due to both side effects and co-morbidities.
Are health care systems insensitive to needs of suicidal patients in times of conflict? The Kashmir experience
Authors: Wani Zaid Ahmad , Hussain Arshad , Khan Abdul Wahid , Dar M Maqbool , Khan AkashYousf , Rather Yasir H. , Shoib Sheikh
Published: December 2011

Suicide and attempted suicide is an important health issue and the number of people who die of suicide exceeds that of conflicts. Kashmir has been suffering from a low intensity war since last 20 years in which thousands have been killed or injured. There has been phenomenal increase in cases of psychological disorders along with suicide and and suicide attempters. Suicide in a conflict zone is viewed with indifference due to focus on the physical part of trauma. Difficulties faced by the suicidal patient and his attendants are seldom highlighted. 1408 patients who reported to emergency room for suicide attempt from 2000 to 2008 were taken for the study. All the patients underwent the hospital protocol for poisoning management. Patients were subjected to detailed psychiatric evaluation and questions were specifically asked about the difficulties encountered during management. Most of the cases were females with 92.11% belonging to the Muslim religion. 76.20% cases were from a rural background. 32.5% had been referred because of the lack of specific antidotes. Forty-three percent required arrangement of transportation by their own family members. Fifty-seven percent had been stopped for security checks along the way. Seventy-three percent felt that the attitude of the staff hostile. Twenty-three percent of patients had to share a bed. Almost all patients were questioned by security agencies within the hospital. More than 68% patient reported hostility amongst their neighbors. Suicidal poisoning is a significant health problem in Kashmir and management of these cases is fraught with difficulties across the spectrum of health care. Educating the doctors at primary care about first aid, improvement in community services followed by long term resolution of the conflict would go some way in alleviating the difficulties faced by a suicidal patient and his family in a conflict zone.
Biomechanical properties of the rectovaginal fascia. Is it really a fascia?
Authors: Glavind Karin , Jespersen Janus Bo , Seyer-Hansen Mikkel
Published: December 2011

Background. The aim of this study was to find out whether the rectovaginal fascia was really a true fascia by comparing the mechanical properties and collagen content of the rectovaginal fascia in women operated for rectoceles to the abdominal fascia in patients having an abdominal hysterectomy. Materials and Methods. Thirty patients were included. During operation for rectocele or hysterectomy a biopsy measuring 8 x 15 mm was taken from the rectovaginal fascia or abdominal fascia. Mechanical testing and measurement of collagen content was performed. Results. A significant difference in mechanical strength of the tissue was found. If, however, the strength was corrected for collagen content there was no difference between the two groups. Conclusion. The quality of collagen was comparable in the two groups. This adds further evidence to the existence of a distinct rectovaginal fascia.
Transvaginal urethral diverticulectomy using small intestinal submucosa interposition graft
Authors: De Baets Karen , De Vylder Ann M. A.
Published: December 2011

Background. Our aim was to evaluate our four and a half year single-center experience with interposition of small intestinal submucosa (SIS) in transvaginal urethral diverticulectomy. Design and methods. We reviewed the records of all patients who underwent a transvaginal diverticulectomy at our center between September 2006 and December 2010. Collected data included demographic details, symptoms, diagnosis, treatment, follow-up, and outcome. Mean time of follow-up was 127 days. Results. Twelve consecutive patients were identified. Mean age was 36 years. Most reported symptoms were a vaginal mass and pain, recurrent urinary tract infections, and urinary stress incontinence. At physical examination a vaginal mass was palpated in all cases. In two out of seven patients cystourethroscopy showed the diverticulum. Magnetic resonance imaging was diagnostic in five out of ten patients who underwent this examination. In all patients a transvaginal diverticulectomy with SIS interposition was performed. In one patient the postoperative course was complicated by a minor postoperative bleeding that needed re-intervention. Two patients developed de novo urinary stress incontinence after surgery. No symptoms of diverticulum recurrence, urethrovaginal fistula, urethral stricture or voiding difficulties were reported. Conclusions. We conclude that SIS is efficient and safe to use as interposition graft in transvaginal urethral diverticulectomy.
Safety and Efficacy of Lenalidomide in Relapsed or Refractory Multiple Myeloma
Authors: Alegre Adrian , Vicuña Isabel , Aguado Beatriz
Published: December 2011

Lenalidomide is an oral immunomodulatory drug that has helped improve outcomes in multiple myeloma (MM) patients. Combination lenalidomide and dexamethasone (Len+Dex) has been shown to increase response rates and prolong survival compared with dexamethasone alone in patients with relapsed or refractory MM (RRMM). Clinical benefit may be greatest when Len+Dex is given at first relapse, and continued treatment appears to provide greater depth of response and improved survival outcomes. The most common adverse events associated with Len+Dex are cytopenias, which are predictable and manageable. Len+Dex is associated with an increased risk of venous thromboembolism, which necessitates adequate prophylaxis. The risk of second primary malignancies does not appear to be increased in patients with RRMM treated with lenalidomide-based therapy. Here we review the safety and efficacy of Len+Dex in RRMM, and provide an overview of data from Spain on the use of Len+Dex in RRMM.
Biochemical and Anthropometric Effects of a Weight Loss Dietary Supplement in Healthy Men and Women
Authors: McCarthy Cameron G. , Canale Robert E. , Alleman Rick J. , Reed Jacob P. , Bloomer Richard J.
Published: December 2011

Background

We have recently noted an acute increase in circulating free fatty acids and glycerol, as well as resting metabolic rate, when men and women ingested the dietary supplement OxyELITE Pro™ in a single dose. We have also noted a reduction in appetite when subjects were treated with this supplement for 14 consecutive days. It is possible that such findings may favor body weight and fat loss over time. Therefore, the purpose of the present study was to determine the effects of this dietary supplement on weight loss and associated markers using an eight week intervention.

Methods

Exercise-trained subjects were randomly assigned in double blind manner to ingest either the dietary supplement (n = 16; aged 22.8 ± 0.7) or a placebo (n = 16; 22.5 ± 0.5) every day for eight weeks. Body weight, body composition, skinfold thickness, serum lipids, and appetite were measured as the primary outcome variables. As measures of supplement safety, a complete blood count and comprehensive metabolic panel were performed, and resting heart rate and blood pressure were measured (pre and post intervention).

Results

No interactions or main effects were noted for our primary outcome measures ( P > 0.05). However, when comparing pre and post intervention values for the supplement, significant decreases were noted in appetite, body weight, body fat percentage, and skinfold thickness ( P < 0.05), while increases were noted for total and HDL-C, as well as for resting heart rate ( P < 0.05). No changes were noted for placebo from pre to post intervention ( P > 0.05), with the exception of an increase in HDL-C ( P < 0.05). Blood pressure and bloodborne safety variables were not differently impacted by supplement or placebo ( P > 0.05), with the exception of monocytes, for which an interaction effect was noted ( P = 0.04).

Conclusion

These data indicate that the dietary supplement OxyELITE Pro™ may assist in weight and body fat loss in a sample of exercise-trained men and women. The supplement does not result in any adverse effects pertaining to resting blood pressure or bloodborne markers of safety; however a small increase in resting heart rate is observed.
Hemodynamic and Hematologic Profile of Healthy Adults Ingesting Dietary Supplements Containing 1,3-Dimethylamylamine and Caffeine
Authors: Farney Tyler M. , McCarthy Cameron G. , Canale Robert E. , Allman Rick J. , Bloomer Richard J.
Published: December 2011

Background

1,3-dimethylamylamine (a constituent of geranium), alone and in combination with caffeine, is widely used within dietary supplements. We have recently determined the hemodynamic effects of 1,3-dimethylamylamine and caffeine alone and in combination, using a single ingestion study. However, no study has determined the hemodynamic effects of these ingredients following chronic use. Moreover, no study has determined the effects of these ingredients on bloodborne variables related to health and safety. Therefore, the purpose of this investigation was to assess the hemodynamic and hematologic profile of two different dietary supplements containing 1,3-dimethylamylamine and caffeine (in addition to other ingredients), before and after two weeks of daily intake.

Methods

7 men (24.9 ± 4.2 yrs) ingested the dietary supplement Jack3d™, while 4 men and 2 women (22.5 ± 1.8 yrs) ingested the dietary supplement OxyELITE Pro™ once per day for two weeks. On days 1 and 15, resting heart rate (HR), systolic (SBP), and diastolic (DBP) blood pressure were measured and rate pressure product (RPP) was calculated. Fasting blood samples were analyzed for complete blood counts, comprehensive metabolic panel, and lipid panel. These tests were done prior to ingestion of supplement. On days 1 and 15 following blood collection, subjects ingested the assigned supplement (2 servings) and HR, SBP, DBP, and RPP were recorded at 30, 60, 90, and 120 minutes post-ingestion.

Results

After 14 days of treatment, resting HR, SBP, DBP, and RPP were not increased ( P > 0.05). No significant changes were noted in any measured bloodborne variable, with the exception of an increase in fasting blood glucose with ingestion of Jack3d™ ( P = 0.02). In response to acute intake of the supplements, HR, DBP, and RPP were not increased statistically ( P > 0.05). SBP was increased with OxyELITE Pro™ ( P = 0.03), but not with Jack3d™ ( P = 0.09). Compared to pre-ingestion and in general, both supplements resulted in an increase in SBP, DBP, and RPP from 5%-15%, with a peak occurring at the 60 or 90 minute post-ingestion time.

Conclusion

Acute ingestion of OxyELITE Pro™, but not Jack3d™, results in an increase in SBP. Chronic intake of two servings per day of OxyELITE Pro™ or Jack3d™ over a 14 day period does not result in an elevation in resting HR, SBP, DBP, or RPP. No significant changes are noted in any measured bloodborne variable following 14 days of ingestion, with the exception of blood glucose with Jack3d™. Longer term intervention studies inclusive of larger sample sizes are needed to extend these findings.
Filters in C*-Algebras
Authors: Matthew Bice Tristan
Published: December 2011

In this paper we analyze states on C*-algebras and their relationship to filter-like structures of projections and positive elements in the unit ball. After developing the basic theory we use this to investigate the Kadison–Singer conjecture, proving its equivalence to an apparently quite weak paving conjecture and the existence of unique maximal centred extensions of projections coming from ultrafilters on the natural numbers. We then prove that Reid's positive answer to this for q-points in fact also holds for rapid p-points, and that maximal centred filters are obtained in this case. We then show that consistently, such maximal centred filters do not exist at all meaning that, for every pure state on the Calkin algebra, there exists a pair of projections on which the state is 1, even though the state is bounded strictly below 1 for projections below this pair. Next, we investigate towers, using cardinal invariant equalities to construct towers on the natural numbers that do and do not remain towers when canonically embedded into the Calkin algebra. Finally, we show that consistently, all towers on the natural numbers remain towers under this embedding.
Asymptotic behavior of global solutions to the Navier–Stokes equations in $\mathbb R^3$
Authors: Planchon Fabrice
Published: December 2011

We construct global solutions to the NavierStokes equations with initial data small in a Besov space. Under additional assumptions we show that they behave asymptotically like self-similar solutions.
Inverse problems in the theory of analytic planar vector
Authors: Sadovskaia Natalia , Ramírez Rafael O.
Published: December 2011

In this communication we state and analyze the new inverse problems in the theory of differential equations related to the construction of an analytic planar vector field from a given, finite number of solutions, trajectories or partial integrals. Likewise we study the problem of determining a stationary complex analytic vector field from a given finite subset of terms in the formal power series

V(z, w) = \lambda (z^2 + w^2) + \sum^\infty_{k=3} H_k (z, w), H-k (az, aw) = a^kH_k(z,w),

and from the subsidiary condition

\Gamma (V) = \sum^\infty_{k=1} G_{2k}(z^2 + w^2)^{k+1},

where

G_{2k}

is the Liapunov constant. The particular case when

V (z,w) = f_0(z,w) – f_0(0,0)

and

(f_0, D \subset \mathbb C^2)

is a canonic element in the neigbourhood of the origin of the complex analytic first integral

F

is analyzed. The results are applied to the quadratic planar vector fields. In particular we constructed the all quadratic vector field tangent to the curve

(y – q (x))^2 – p(x) = 0.

where

q

and

p

are polynomials of degree

k

and

m ≤ 2k

respectively. We showed that the quadratic differential systems admits a limit cycle of this type only when the algebraic curve is of the fourth degree. For the case when

k > 5

it proved that there exist an unique quadratic vector field tangent to the given curve and it is Darboux's integrable.
The resolution of the Navier-Stokes equations in anisotropic spaces
Authors: Iftimie Dragoș
Published: December 2011

In this paper we prove global existence and uniqueness for solutions of the dimensional Navier–Stokes equations with small initial data in spaces which are

H^{\delta_i}

in the i-th direction,

\delta_1 + \delta_2 + \delta_3 = 1/2, –1/2 < \delta_i < 1/2

and in a space which is

L^2

in the first two directions and

B^{1/2}_{2,1}

in the third direction where

H

and

B

denote the usual homogeneous Sobolev and Besov spaces.
Controllability of analytic functions for a wave equation coupled with a beam
Authors: Allibert Brice , Micu Sorin
Published: December 2011

We consider the controllability and observation problem for a simple model describing the interaction between a fluid and a beam. For this model microlocal propagation of singularities proves that the space of controlled functions is smaller that the energy space. We use spectral properties and an explicit construction of biorthogonal sequences to show that analytic functions can be controlled within finite time. We also give an estimate for this time related to the amount of analyticity of the latter function.
On the regularity of the bilinear term for solutions to the incompressible Navier-Stokes equations
Authors: Cannone Marco , Planchon Fabrice
Published: December 2011

We derive various estimates for strong solutions to the Navier-Stokes equations in

C(|0,T)

,

L^3 (\mathbb R^3)

that allow us to prove some regularity results on the kinematic bilinear term.
Global orthogonality implies local almost-orthogonality
Authors: Wilson J. Michael
Published: December 2011

We introduce a new stopping-time argument adapted to handle linear sums of noncompactly-supported functions that satisfy fairly weak decay smoothness and cancellation conditions. We use the argument to obtain a new Littlewood-Paley-type result for such sums.
Multi-multifractal decomposition of digraph recursive fractals
Authors: Simpelaere Dominique
Published: December 2011

In many situations both deterministic and probabilistic, one is interested in measure theory in local behaviours, for example in local dimensions, local entropies or local Lyapunov exponents. It has been relevant to study dynamical systems since the study of multifractal can be further developped for a large class of measures invariant under some map, particularly when there exist strange attractors or repelers (hyperbolic case). Multifractal refers to a notion of size which emphasizes the local variations of the weight of a measure of the entropy or the Lyapunov exponents. All these notions are explicited in the case of digraph recursive fractal studied by Edgar & Mauldin where some questions are given. We study the extremal measures and introduce the notion of multimultifractality which may be useful in problems of rigidity.
On the 1/2-Problem of Besicovitch: quasi-arcs do not contain sharp saw-teeth
Authors: Farag Hany M.
Published: December 2011

In this paper we give an alternative proof of our recent result that totally unrectifiable 1-sets which satisfy a measure-theoretic flatness condition at almost every point and sufficiently small scales, satisfy Besicovitch's 1/2-Conjecture which states that the lower spherical density for totally unrectifiable 1-sets should be bounded above by 1/2 at almost every point. This is in contrast to rectifiable 1-sets which actually possess a density equal to unity at almost every point. Our present method is simpler and is of independent interest since it mainly relies on general properties of finite sets of points satisfying a scale-invariant flatness condition. For instance it shows that a quasi-arc of small constant cannot contain "sharp saw-teeth".
Uniformly convex operators and martingale type
Authors: Wenzel Jörg
Published: December 2011

The concept of uniform convexity of a Banach space was generalized to linear operators between Banach spaces and studied by Beauzamy. Under this generalization, a Banach space

X

is uniformly convex if and only if its identity map

I_X

is. Pisier showed that uniformly convex Banach spaces have martingale type

p

for some

p>1

. We show that this fact is in general not true for linear operators. To remedy the situation, we introduce the new concept of martingale subtype and show, that it is equivalent, also in the operator case, to the existence of an equivalent uniformly convex norm on

X

. In the case of identity maps it is also equivalent to having martingale type

p

for some

p>1

. Our main method is to use sequences of ideal norms defined on the class of all linear operators and to study the factorization of the finite summation operators. There is a certain analogy with the theory of Rademacher type.
Harnack’s inequality for solutions of some degenerate elliptic equations
Authors: Mohammed Ahmed
Published: December 2011

We prove a Harnack’s inequality for non-negative solutions of some degenerate elliptic operators in divergence form with the lower order term coefficients satisfying a Kato type condition.