The fine structure of bicomponent polyester fibers

The application of alkaline hydrolysis to study the change in the fine structure of bicomponent polyester fibers as their surface is removed progressively was explored. The samples were prepared with a poly(butylene terephthalate) (PBT) sheath and a poly(ethylene terephthalate) (PET) core. The reagent used to hydrolyze the PBT was 1M NaOH in 75/25 methanol to water since it appeared to react topochemically with the fiber. The solution reacted more rapidly with PET than with PBT. Thus, when necessary to retard the weight loss of the bicomponent fibers, after a 2‐h hydrolysis with this reagent to remove PBT, it was replaced with aqueous 1M NaOH solution containing 0.1% cetrimmonium bromide. Unlike homofil PET or PBT fibers, where alkaline attack appeared to be confined to the surface and left the residue relatively smooth, the bicomponent fiber was attacked unevenly, and penetration to the PET core occurred before all the PBT at the surface was removed. Nevertheless, most of the reaction was confined initially to the PBT sheath. The tenacity and extension at break of the PBT–PET fiber passed through a maximum as hydrolysis progressed. The fall in tenacity at high weight losses is ascribed to increasing surface defects in the fiber surface. After removal of the PBT by the hydrolysis, the birefringence of the residue became progressively higher. The synergistic effect of the PBT sheath on the properties of the PET core and the possible causes of the nonuniform hydrolysis at the PBT surface are discussed. An equation is proposed that includes an interaction parameter, which can be utilized to determine which property is affected most by the hydrolysis of a bicomponent fiber. In this instance, it appears from the parameters that the order is strength > extension at break ≈ birefringence. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1163–1173, 1999     

Effect of Silicon Nitride Ball on Adhesive Wear of Martensitic Stainless Steel Pyrowear 675 and AISI M-50 Races with Type II Ester Oil

Advanced bearing materials for future military and commercial gas turbines are required to operate at high speeds, high temperature, and higher thrust loads. At elevated operating conditions, the bearing and gear materials must be able to operate with ultrathin oil films without suffering detrimental effects of adhesive wear. The development of materials with rolling-element fatigue and corrosion resistance properties without deterioration in adhesive wear attributes is a significant challenge. To meet those performance requirements, the forerunner, martensitic stainless steel Pyrowear 675 (AMS 5930), has been in development for aerospace bearing and gear applications. This article addresses the adhesive wear performance of three variants of Pyrowear 675 with silicon nitride ball material simulating a hybrid bearing evaluated using a WAM8 machine. Baseline testing was conducted using conventional bearing steel AISI M-50. Adhesive wear testing was conducted at a temperature of 200°C and at different contact slips (15, 30, 50, and 70%) and entraining velocities (1.3 to 10.2 m/s). Posttest specimens were analyzed by scanning electron microscopy (SEM) and auger electron spectroscopy (AES). All the hybrid material pairs demonstrated very good adhesive wear performance compared to the baseline AISI M-50–AISI M-50 pair.     

Video-assisted thoracoscopic placement of paravertebral catheters: a technique for postoperative analgesia for bilateral thoracoscopic surgery

Paravertebral catheters were placed bilaterally through a Tuohy needle under direct video control in a patient undergoing video-assisted thoracoscopic (VAT) surgery for recurrent, bilateral pneumothoraces. Postoperative analgesia was produced by infusing bupivacaine through the catheters. This provided good analgesia. VAT placement of paravertebral catheters is easily accomplished and may be a part of the surgical procedure.     

Cuckoo search algorithm based satellite image contrast and brightness enhancement using DWT–SVD

This paper presents a new contrast enhancement approach which is based on Cuckoo Search (CS) algorithm and DWT-SVD for quality improvement of the low contrast satellite images. The input image is decomposed into the four frequency subbands through Discrete Wavelet Transform (DWT), and CS algorithm used to optimize each subband of DWT and then obtains the singular value matrix of the low-low thresholded subband image and finally, it reconstructs the enhanced image by applying IDWT. The singular value matrix employed intensity information of the particular image, and any modification in the singular values changes the intensity of the given image. The experimental results show superiority of the proposed method performance in terms of PSNR, MSE, Mean and Standard Deviation over conventional and state-of-the-art techniques.     

Morphological and microchemical phenomena in the high-temperature oxidation of binary Al-Li alloys

The high-temperature oxidation behavior of binary Al-Li alloys has been characterized by scanning electron microscopy and secondary ion mass spectrometry in order to understand the mechanism of rapid oxidation in these alloys and to correlate the oxide morphology to its microchemistry. The oxide scale developed on polished specimens during short exposures in air at 530°C shows characteristic nodules that usually nucleate at grain boundaries. Examination of the alloy surface after removal of the oxide layer shows that the initial growth of the oxide nodules occurs laterally in addition to thickening normal to the oxide/alloy interface. Microchemical analysis of the oxide film with a scanning ion microprobe reveals a thick Li-oxide layer at the oxide/gas interface indicating preferential oxidation of Li at the free surface; the rest of the oxide film is composed of both Al- and Li-rich oxides, probably Li₂O and LiAlO₂ The presence of trace impurities (K, Na, F, and Cl) in the oxide scale was also detected. A microstructural model for the development of the oxide film in the Al-Li system is presented on the basis of both morphological and microanalytical data obtained in this study; this new model is compared with existing models.     

Performance analysis of evacuated tubes coupled solar still with double basin solar still and solid fins

ABSTRACT

Experimental set up of double basin solar still with evacuated tubes has been fabricated by locally available materials and then carry out research work by use of solid fins. Here 2.5?cm constant depth of water maintained and 3?cm depth mild steel fins are used. Experimental results have been obtained during month of March and April 2018 during clear sky days. Month of March 2018 is chosen for experiments on double basin solar still with evacuated tubes only and April 2018 is chosen for experiments on double basin solar still with evacuated tubes and fins. After series of experiments, it has been found that, the fins increase 25% distillate output compared with alone double basin solar still with evacuated tubes. It also increases distillate output during sunshine hours as well as off-sunshine hours.     

Critical current density and magnetization studies on Bi(Pb)SrCaCuO

HighT _c phase (T _c ∼ 110 K) has been obtained in Bi-Sr-Ca-Cu-O system by partially substituting Bi by Pb. Magnetic hysteresis has been measured as a function of temperature. Critical current densities have been measured at 77 K both by transport and a.c. magnetization method in bulk samples for various concentrations of Pb. The results show that substitution of 15 at % Pb for Bi is most preferable for higher critical current density.