The study of minor elements and shielding gas on penetration in TIG welding of type 304 stainless steel

The effects of minor elements and shielding gas on the penetration of TIG welding in type 304 stainless steel have been studied. The bead-on-plate test was performed, then the depth and width of the weld were measured using an optical projection machine. The arc voltage was measured with an arc data monitor. In addition, the metallurgical characteristics of weld were examined using OM and SEM. The results show that oxygen and sulfur are beneficial in increasing a depth/width ratio because of the increased surface tension/temperature gradient. Elements, such as aluminum, that have a deleterious effect on the depth/width ratio will combine with oxygen and reduce the soluble oxygen content in the weld pool. On the other hand, silicon and phosphorus have a minor effect on the depth/width ratio. Shielding gas using Ar + 1% O₂ or Ar + 5% H₂ can significantly promote the depth/width ratio. The former contains increased soluble oxygen content in the weld pool, and the latter produces an arc that is hotter than that produced by pure argon.     

Structure–property correlation for thin films of semi-interpenetrating polyimide networks. I. Miscibility,curing, and morphology studies

Three different semi-interpenetrating polymer network (semi-IPN) polyimide systems were prepared through blending in solution by using 2 different polyimides, BPDA–PDA and PMDA–ODA (E), and 2 different oligomers, bismaleimide (MDAB) and phenylthynyl-terminated BPDA–PDA (BPDA–PDA–PEPA) oligomers. The oligomers are used as crosslinkers to modify the morphology of polyimides. The results show that both MDAB and PEPA are miscible with BPDA–PDA, but MDAB is immiscible with PMDA–ODA (E). Fourier transform infrared spectrum, dynamic mechanical thermal analysis data, and calculated crosslinking density indicate that there are crosslinking networks in these semi-IPN polyimide systems. In addition, the density and wide-angle X-ray diffraction results confirm that the molecular ordering and packing order are reduced by the addition of oligomers for these semi-IPN polyimide systems. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 261–272, 1998     

On a transistor-type hydrogen gas sensor prepared by an electrophoretic deposition (EPD) approach

A Pd/GaN/AlGaN heterostructure field-effect transistor (HFET)-type hydrogen gas sensor, based on an electrophoretic deposition (EPD) approach, is fabricated and studied. Due to the formation of good Schottky gate contact by an EPD approach, the studied HFET shows improved DC performance including the suppressed gate current and better thermal stabilities on current–voltage (I–V) characteristics. This is mainly attributed to the reduction of interface trap density and improved Pd morphology. The EPD-based Pd morphologies are examined by X-ray diffraction, energy dispersive spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and atomic force microscopy. For the used gate-dimension of 1 μm × 100 μm, an EPD-based HFET shows low gate current of 2.9 nA, maximum drain saturation current of 490 mA/mm, and maximum extrinsic transconductance of 78.9 mS/mm at room temperature. Also, solid thermal stabilities on maximum drain saturation current (−0.46 mA/mm K) and maximum extrinsic transconductance (−0.08 mS/mm K) are found as the temperature is increased from 300 to 600 K. For hydrogen gas sensing application, at 370 K, the maximum hydrogen sensitivity of 600.1 μA/mm ppm H₂/air under a 5 ppm H₂/air ambiance and fast response time (30 s) and recovery time (47 s) under a 10,000 ppm H₂/air ambiance are obtained. The EPD approach also demonstrates advantages of low cost, simple apparatus, easy process, little restriction on the shaped substrate, composited deposition, and adjustable alloy grain size. Therefore, the proposed EPD approach gives the promise for fabricating high-performance HFET devices and hydrogen gas sensors.     

An investigation of the effect of laser deposition parameters on characteristics of multilayered 316 L deposits

A potential problem in applying the direct laser deposition (DLD) technique to material fabrication is the effect that subsequent deposited layers have on reheating previous laser deposition layers. Most of the previous investigations examined the effect of the laser deposition parameters on the microstructure and mechanical properties of a single layer. This work focused on the effect of the laser parameters of subsequent layers on the microstructure and mechanical properties of the deposited layers to select proper parameters and characterize the effect. The microstructure morphology and property values are affected by the varied parameters. This leads to some tempering and aging effects in the steels. The microstructure of the top layer was equiaxed, while the near substrate region was fine dendritic. Typically, both of the travel speed and power of the laser show the significant effects on microstructure and hardness.     

Robust Digital Terrestrial TV Broadcasting System with Error-Resilient Schemes

In this paper, error-resilient schemes are proposed to support robust video transmission for digital terrestrial TV broadcasting (DTTB). In particular, a temporal error concealment incorporated with a low-complexity block-matching is developed, achieving an effective reception of predictive pictures in harsh terrestrial environment. Special algorithms are also designed for isolated I-pictures. Moreover, combined with an intra/inter case prediction, an adaptive error concealment scheme is further contrived to fit for different error conditions. Extensive simulations have been conducted under various DTTB channel conditions, even with a very high packet error rate, to verify the effectiveness of the proposed schemes.     

Synthesis of Pb(Ni1/3Nb2/3)0.72Ti0.28O3 perovskite ceramics by a reaction-sintering process

Pb(Ni_1/3Nb_2/3)_0.72Ti_0.28O₃ (PNNT) perovskite ceramics produced by a reaction-sintering process were investigated. Without any calcination, the mixture of PbO, Ni(NO₃)₂, Nb₂O₅ and TiO₂ was pressed and sintered directly into PNNT ceramics. PNNT ceramics of 100% perovskite phase were obtained. For PNNT sintered for 2 h in PbO compensated atmosphere, maximum density reaches a value 8.49 g/cm³ (99.8% of the theoretical value) at 1250^∘C. A maximum dielectric constant 20600 occurred around 37^∘C at 1 kHz in PNNT sintered at 1250^∘C for 2 h.     

Novel Haar features for real-time hand gesture recognition using SVM

Journal of Real-Time Image Processing - Due to the effect of lighting and complex background, most visual hand gesture recognition systems work only under restricted environments. Here, we propose...     

茅苍术挥发油化学成分的GC/MS分析

采用水蒸气蒸馏法从茅苍术中提取挥发油。试用不同类型的毛细管柱进行分析,找出最佳分析条件,用归一化法测定其百分含量,用气相色谱-质谱法对茅苍术挥发油化学成分进行鉴定。共鉴定了57个成分,占挥发油总成分的82％以上。本方法稳定可靠,重现性好,适用于中药挥发油的化学成分分析。     

Study of Residual Stress Distribution in the Machined Stainless Steel Components

The demand for high quality and fully automated production, coupled with advances in alloy development, focuses attention on the surface condition of products, especially the residual stresses on the machined surface because of its effect on component performance, longevity, and reliability. Although stainless steel is an important, material with wide application, it is not easy to obtain favorable surface condition, due to its sensitivity to thermal and mechanical operations. In order to obtain favorable surface conditions in a stainless steel component, it is necessary to have practical data which include information concerning tool wear, surface roughness and surface residual stress. In the research toward developing a machinability chart which can provide suitable cutting parameters for the high production rate and good quality surface, and can be used in computer controlled machining tools, surface residual stress distributions in the turning process for stainless steel were studied. Austenitic 304 stainless steel bars were selected as the workpieces and uncoated carbide tools were used in the tests. The obtained results will show residual stress conditions on the machined stainless steel components varying according to cutting conditions.     

A parallel technique for signal-level perceptual organization

Due to the potential for essentially unbounded scene complexity, it is often necessary to translate the sensor-derived signals into richer symbolic representations. A key initial stage in this abstraction process is signal-level perceptual organization (SLPO) involving the processes of partitioning and identification. A parallel SLPO algorithm that follows the global hypothesis testing paradigm, but breaks the iterative structure of conventional region growing through the use of α-partitioning and region filtering is presented. These two techniques segment an image such that the gray-level variation within each region can be described by a regression model. Experimental results demonstrate the effectiveness of this algorithm