Effects of Plasticizers,Antioxidants and Burning Rate Modifiers on Aging Performance of the HTPB/HMDI Composite Solid Propellant

The effects of plasticizers,antioxidants and burning rate modifiers on the aging performance of the composite solid propellant based on hydroxyl-terminated polybutadiene(HTPB)/hexamethylene diisocyanate(HMDI)were explored by apply-ing an accelerated aging program for 90 day at 70 ℃. The HTPB propellant matrix with the diisooctyl sebacate(DOS)as plasti-cizers and diisooctyl azelate(DOZ), antioxidants as N,N ′-Diphenyl-p-phenylenediamine(AO) and 2,2′-methylenebis(4-methyl-6-tert-butylphenol)(cyanox 2246)and burning rate modifiers as barium ferrite(BF),copper chromites(CC)and fer-ric oxide(FO)were varied. Results show that sample(S1)which based on DOS decreases the stress value and increases the strain value which considered to be an excellent start for aging program. Sample(S3)containing AO presents the higher resis-tance to oxidation showing the better performance that reflects on increasing the shelf life of the composite solid propellant mo-tor. Sample(S5)which based on BF enhances the ballistic performance among over the other tested two samples. The accelerat-ed aging program allowed us to estimate the motor in-service lifetime.     

Evaluation of acupuncture and occlusal splint therapy in the treatment of temporomandibular joint disorders

One hundred patients showed signs and symptoms of temporomandibular joint disorder, were participated in a one year follow up study. The patients were randomly divided into four groups: Acuhealth treatment (group A), occlusal splint therapy (group B), Acuhealth and occlusal splint therapy (group C), and control (group D). Each group comprised 25 patients. The patients were examined before and 3, 6, and 12 months after treatment. At the three month evaluation, the patients who were not satisfied with the treatment outcome were offered additional treatment. The result showed that 87% of the patients treated by Acuhealth unit, 77.3% of the patients treated with occlusal splint therapy, and 91.3% of the patients received Acuhealth and occlusal splint therapy were improved subjectively and clinically after 3 months follow-up. The patients who responded well to treatment initially also responded well in the long run. The study showed that the Acuhealth unit proved to be an ideal early therapy for TMD, and complemented later with occlusal splint.     

Preparation and Properties of PBXs Based on FOX-7 in Controlled Fragmentation Warhead Application（英）

Polymer bonded explosive(PBX)formulations were successfully prepared in the laboratory scale containing 1,1-diamino-2,2-dinitroethene(FOX-7)and hexogen(RDX)as brisant high explosives and different binder types of polyurethane(PU)based on glycidyl azide polymer(GAP) and hydroxyl-terminated polybutadiene(HTPB) as an energetic and inert polymeric binder respectively.Casting technique was used for the preparation of different PBX formulations based on FOX-7/RDX and PU(GAP/HTPB)with 14% binder.The sensitivity to different initial impulses and performance characteristics of the explosive and lethal zone of the tested controlled fragmentation warhead by the fragmentation warhead assessment test(arena test)were studied,in which the arena test was carried out with a controlled fragmentation warhead made from Ck45 steel,with dimensions(100 mm length,30 mm outer diameter and 3 mm thickness).Results show that PBXGF4 has lower sensitivity to impact and heat than those of PBXGR4 by 188.4% and 3.2% respectively.Its friction sensitivity is the same as that of PBXGR4.It has better performance,in which detonation velocity increases by 2.1% and brisance increases by 0.5% when compared with those of PBXGR4.It was concluded that PBXGF4 which based on FOX-7 bonded with PU/GAP matrix has good characteristics as PBX,specially in the sensitivity to impact and can be applied for replacing PBXs based on RDX in the advanced PBXs for low sensitive fragmentation warheads.     

Surface roughness effect on finite journal bearings with flexible porous liners

The effects of surface roughness on the static characteristics of finite porous journal bearings under hydrodynamic lubrication conditions are investigated in this paper. The well‐established Christensen stochastic theory of hydrodynamic lubrication of rough surfaces is used to incorporate the effects of surface roughness into the Reynolds equation. The analysis takes into account the flexibility of the porous liner by using a thin liner model. The effects of velocity slip at the surface of the porous medium are considered in the analysis by using the Beavers‐Joseph criterion. The mathematical model is then solved numerically by finite‐difference methods for mean hydrodynamic pressure, which in turn gives the hydrodynamic load. The effects of the surface roughness parameter, surface pattern, eccentricity ratio, length‐to‐diameter ratio, permeability parameter, and flexibility parameter on the hydrodynamic load‐carrying capacity, attitude angle, and friction factor are discussed.     

Hydrodynamic lubrication of porous journal bearings using a modified Brinkman-extended Darcy model

A numerical solution for the hydrodynamic lubrication of finite porous journal bearings considering the flexibility of the liner is introduced. The Brinkman-extended Darcy equations and the Stokes' equations are utilized to model the flow in the porous region and fluid film region, respectively. A stress jump boundary condition at the porous media/fluid film interface and effects of viscous shear are included into the lubrication analysis. Elrod's cavitation algorithm, which automatically predicts film rupture and reformation in the bearing, is implemented in the solution scheme. The present analysis predictions for pressure distributions, load carrying capacity, and friction factor are in good agreement with three different sets of experimental results available in the literature. Furthermore, the effects of dimensionless permeability parameter, and stress jump parameter on performance parameters such as load carrying capacity, side leakage, friction factor, and attitude angle, are presented and discussed.     

Effect of grinding forces on the vibration of grinding machine spindle system

In this paper the effects of dynamic changes in the grinding force components due to changes in the grinding wheel wear flat area and the workpiece material on the vibration behavior of the grinding spindle are studied. The steady-state dynamics and vibration behavior of the grinding machine spindle is simulated by a five degree of freedom model. The results indicate that when grinding different materials using a grinding wheel with fixed wear flat area, different vibration behavior is noticed. As the grinding wheel flat area increases, the level of vibration increases for all the degrees of freedom, which indicates that there is an upper limit for the level of wear on the grinding wheel that can be tolerated, and after that level dressing operation must be conducted on the grinding wheel.     

Predicting the Bubble-Point Pressure and Formation-Volume-Factor of Worldwide Crude Oil Systems

This paper presents models for predicting the bubble-point pressure (P_b) and oil formation-volume-factor at bubble-point (B_ob) for crude oil samples collected from several regions around the world. The regions include major producing oil fields in North and South America, North Sea, South East Asia, Middle East, and Africa. The model was developed using artificial neural networks with 5200 experimentally obtained PVT data sets. This represents the largest data set ever collected to be used in developing P_b and B_ob models. An additional 234 PVT data sets were used to investigate the effectiveness of the neural network models to predict outputs from inputs that were not used during the training process. The network model is able to predict the bubble-point pressure and the oil formation-volume-factor as a function of the solution gas-oil ratio, the gas relative density, the oil specific gravity, and the reservoir temperature. In order to obtain a generalized accurate model, back propagation with momentum for error minimization was used. The accuracy of the models developed in this study was compared in details with several published correlations. This study shows that if artificial neural networks are successfully trained, they can be excellent reliable predictive tools to estimate crude oil properties better than available correlations. The network models can be easily incorporated into any reservoir simulators and/or production optimization software.     

Anti-inflammatory and Chemical Composition of Two Plants Family Asteraceae Growing in Saudi Arabia

The study was designed to investigate the anti-inflammatory and composition of essential oil of two plant family Asteraceae, Achillea fragrantissima and Lactuca serriola growing under dry desert condition. The anti-inflammatory effect of volatile oil extracted by hydrodistillation of plants was studied using carrageenan induced paw edema. Essential oil （100 mg/kg） and （200 mg/kg） were tested the two plant show high inhibition after 4 h, concentration （200 mg/kg） show high inhibition than （100 mg/kg） after 4 h. Sesqui sabinene hydrate, Azuline and u-Bisabolol are the main constituents of the volatile oil were investigated by capillary GC （gas chromatography） and GC-MS （gas chromatography-mass spectrometry）. The discussion shows the role of chemical compound azulene in inflammatory inhibition.     

Stretch-bending analysis of U-section beams

A complete analysis for stretch-bending of U-section beams is introduced. The variations of the applied bending moment with the applied axial load for fully elastic, elastic-plastic and fully plastic conditions are derived. The ultimate goal of such simulation technique is to develop a simple and fast technique to determine stresses, strains, springback and residual stresses as functions of parameters such as material characteristics, forming loads and the required geometry of U-section beams. The model proposed in the present study can be considered as a major step for computer simulation of stretch-bending at the design stage which will provide useful data and criteria for equipment selection and tooling design. The significance of various material parameters from productibility, ease of fabrication and tool design viewpoints can also be evaluated by the model. Furthermore, the failure modes of the stretch-bending process are also introduced and the region for safe operations are defined in a very useful and practical set of curves.     

Thermal Analysis Studies of (Bi,?Pb)-2223/Linear Low Density Polyethylene Composite Materials

Series of superconductor/polymer composites were prepared using high-temperature superconductor Bi_1.8Pb_0.4Sr₂Ca_2.1Cu_3.2O_10+?? phase and linear low density polyethylene (LLDPE). The LLDPE concentration varied from 0.0 to 100 wt. % of the sample??s total mass. The composite materials were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), whereas the crystallization point of LLDPE and its composites were determined using differential scanning calorimetery (DSC). Furthermore, the thermal expansion measurements for composite materials were taken from room temperature up to 160?°C. The results showed that the thermal expansion coefficient increased with increasing of the percentage of LLDPE content.