Joining of NiAl to iron-based alloys by reactive casting

Nickel monoaluminide, NiAl, is exothermically synthesized from elemental liquids of aluminum and nickel and is simultaneously joined to iron-based alloys, such as carbon steels and stainless steels, by the reactive casting method, which is based on the pouring of the elemental liquids onto the base material. The exothermic reaction between the aluminum and nickel liquids produces extremely superheated NiAl liquid. Heat of the NiAl liquid is transferred to the base material, and the contact surface is melted to a depth depending on both the preheating temperature of the base material and the thickness of the NiAl produced. After solification on the base material, NiAl is strongly joined to the base material, showing a joint strength exceeding the inherent strength of NiAl. The high joint strength is attributed to a very fine, rodlike eutectic structure at the joint interface that consists of a mixture of β-NiAl and γ-iron with an interrod spacing of approximately 100 nm.     

Seeding effects on solidification behavior of cocoa butter and dark chocolate. I. Kinetics of solidification

Effects of seeding of fat crystals on the crystallization kinetics of cocoa butter and dark chocolate were examined with a rotational viscometer. The seed crystals employed were cocoa butter, 1,3-distearoyl-2-oleoylglycerol (SOS), 1,3-dibehenoyl-2-oleoylglycerol (BOB) and 1,2,3-tristearoylglycerol (SSS). The seed powders were prepared by pulverization below —50°C, the dimensions being in a range from 20–70 μm. Particular attention was paid to the influence of polymorphism of the seed crystal. We found that all of the above seed materials accelerated the crystallization, the degree of acceleration being in a following order; SOS (β ₁) > cocoa butter (Form V) > SOS (a mixture ofβ’ andβ ₂) > BOB (β ₂) > BOB (pseudo-β’) > SSS (β). Precise measurements of the crystallization kinetics showed that the most influential factors in the seeding effects are the physical properties of the seed materials—above all, thermodynamic stability, and similarity in the crystal structure to cocoa butter are the most determinative.     

Preparation of Aluminum Oxynitride and Nitride Spherical Powders Via Flame Synthesis Assisted by DC Arc Plasma

Spherical powders of aluminum oxynitride/nitride are directly prepared by flame synthesis in which oxygen serves as an indispensable reactant. Nonoxide powders are commonly nonspherical, and the particle sizes of these powders are less than submicrometers. The major limiting factors for the synthesis are the free energy, reaction temperature, and reaction rate. The innovative issue related to this flame technology that is assisted by plasma is the ambivalence of the reducing gas atmosphere over 1500 K. The chemical equilibrium calculated indicates that the plasma heating compensates for the lack of reaction temperature under a low-oxygen condition. This burner realizes a high-speed reaction with the help of the reactive species in the arcs.     

Care and feeding of the usability laboratory at Symantec Corporation: a survival guide

This paper discusses the process of planning, building, and managing the usability laboratory at Symantec Corporation. It describes how an effective lab can be built for about $55,000 in equipment and furniture costs, and discusses issues and trade-offs surrounding the key components: room layout, environmental considerations, cabling, one-way mirrors, furniture, video and audio equipment, and data loggers. In addition, one working solution to the subsequent management of a lab with limited staffing and tight product schedules is described.     

Kinetics of melt crystallization and transformation of tripalmitin polymorphs

The rates of melt crystallization and phase transformation of three polymorphs of tripalmitin were examined by optical microscopy, X-ray diffractometry and DSC with and without surfactant additives (sorbitan mono- and tristearates). The following results were obtained: (a) Crystallization rate increased in order ofα, β′ andβ; (b) transformation rate was slower than crystallization rate for each polymorph at the same temperature examined; (c) when the most stableβ form was recrystallized from the melt just after the melting ofα, its recrystallization rate was much higher than that by simple melt-cooling; (d) surfactant additives retarded both the crystallization and transformation of all the polymorphs, yetβ′ was influenced the most. A mechanistic interpretation based on the molecular structures both of the melt and of each polymorph is presented.     

A Fuzzy Behavior-Based Control for Mobile Robots Using Adaptive Fusion Units

It is known that a behavior-based control approach is effective for acquiring an intelligent control system of robots. However, further improvements are required for making any behavior-based control system robust against changes in the environments. A module learning method has been applied in the framework of fuzzy behavior-based control to have an adaptive behavioral fusion. In this paper, an adaptive fusion strategy is proposed to adaptively select a cooperative fusion unit or competitive fusion unit, depending on the external sensor information. Some simulations are given to illustrate that the present control systems are flexible against the change of environments or untrained environments, compared to those with a conventional priority-based fusion unit.     

First On-Wafer Power Characterization of MMIC Amplifiers at Sub-Millimeter Wave Frequencies

We present on-wafer power measurements of 35 nm gate length InP HEMT amplifiers at 330 GHz. Various amplifiers are examined. The maximum output power of 1.78 mW is measured from a three stage amplifier. Additional output power may be possible but limited by our input power source level to saturate amplifiers. This result is the highest frequency on-wafer power measurement we are aware of reported to date, and demonstrates the technique we utilize to be a fast method of evaluating power performance of submillimeter wave amplifiers without the need to package devices.