Development of sintered Ti-30mass%Mo alloy and its corrosion properties

Ti-30mass%Mo alloy is characterized by far better corrosion resistance than pure titanium in non-oxidizing acid such as 35% HC1 solution. This alloy was newly developed in this work by a powder metallurgical process, because the conventional melting-casting process had difficulties in manufacturing the alloy owing to its heavy gravity segregation. The corrosion behavior of sintered Ti-30Mo alloy was studied by both immersion test and electro-chemical measurement. The corrosion rate of 1.3X10⁻²[mm/yearxxx] was obtained by immersion test in 35% HC1 solution, which was 10³ times superior to that of pure titanium. The potentio-dynamic polarization curve of this alloy in 35% HC1 solution showed more noble corrosion potential and lower anodic current density than those of pure titanium. The passive film formed on the alloy, in which Mo was enriched by preferential dissolution of titanium, thought to suppress the anodic reaction and improve its corrosion resistance.     

The damping capacity improvement of machine tool structures by balls packing

Efficient manufacturing is achieved by the damping capacity improvement of machine tool structure. The purpose of this study is to clarify the parameters influencing the damping capacity of machine tool structures packed with balls. In structures closely packed with balls, various damping characteristics appear in correspondence with the ball size and other conditions. The effect of ball size is the most significant factor in these structures. Excitation of structure is necessary for close packing, however, this process is troublesome. Excitation of structure is required to achieve an optimum packing ratio where the maximum damping capacity is obtained. For a 50% packing ratio, this excitation process is not necessary to obtain a stable damping capacity. Therefore, the effects of magnitude of impulse, packed ball material, and structure size on the damping capacity are investigated at a 50% packing ratio. Finally, actual machine tool structure models are constructed, and the effectiveness of the balls packing for the damping capacity improvement is investigated.     

Deployment of wireless mesh network using RSSI-based swarm robots

This paper proposes a novel method for deploying a wireless mesh network (WMN) using a group of swarm robots equipped with wireless transceivers. The proposed method uses the rough relative positions of the robots estimated by their Radio Signal Strength Indicators (RSSIs) to deploy the WMN. The employed algorithm consists of three parts, namely, (1) a fully distributed and dynamic role decision method among the robots, (2) an adaptive direction control using the time difference of the RSSIs, and (3) a narrow corridor for the robots to pass by movement function along walls. In our study, we evaluated the performances of the proposed deployment method and a conventional method in a real environment using 12 real robots for simple deployment, and 10 real robots for passing the narrow corridor. The results of the performed experiments showed that (1) the proposed method outperformed the conventional method with regard to the deployment time, power consumption, and the distances traveled by the robots, and (2) the movement function along the walls is effective while passing a narrow corridor unlike any other function.     

Fracture toughness of adhesive joints. I. Relationship between strain energy release rates in three different fracture modes and adhesive strengths

The three strain energy release rates, G_IC, G_IIC, and G_IIIC, of adhesive joints can be attributed to their ability to resist crack propagation of solids in the adhesive layer. The dependencies of G_IC, G_IIC, and G_IIIC on crack lengths for various adhesive joints were determined using the double-cantilever beam specimen by a compliance method. The two types of adhesive strengths, i.e., adhesive tensile strength and adhesive shear strength, corresponding to G_IC and G_IIC, respectively, were carried out at room temperature and 65% RH with a crosshead speed of 10 mm/min. The G_IC, G_IIC, and G_IIIC were dependent upon crack length and had constant values irrespective of geometric parameters of the specimen over the crack length of five times adherend thickness, 0.65 (= crack length over half a length of span) and eight times adherend thickness, respectively. In the region of the crack length, we determined the following increasing order of fracture toughness: G_IC < G_IIIC < G_IIC. A positive correlation was found between adhesive tensile strength and G_IC. A significant relation between adhesive shear strength and G_IIC was not found in this work. Further studies are needed to clarify the relation between adhesive shear strength and G_IIC with general adhesives. © 1994 John Wiley & Sons, Inc.     

Synthesis of single phase Ca-α-SiAlON using Y-type zeolite

Single phase Ca-α-SiAlON was synthesized for the first time by the carbothermal reduction-nitridation of a physical mixture of Y-type zeolite and CaO. Under well-optimized conditions, which included both a Si/Al ratio of 2.8 for the starting Y-type zeolite and a Ca/Al ratio of 0.63–0.75, highly crystalline, pure Ca-α-SiAlON was obtained. The formation of pure Ca-α-SiAlON was also confirmed by ²⁷Al and ²⁹Si MAS NMR measurements.     

An Efficient Synthesis of Chiral Alcohols via Catalytic Hydrogenation of Esters

A ruthenium complex was found to catalyze the hydrogenation of chiral esters without the loss of their optical purities under mild and neutral conditions. This method can avoid a violent quench step and an extraction step which accompany conventional reduction using metal hydride reagents such as sodium borohydride and lithium aluminum hydride.     

Effects of Rice Straw on the Color and Microstructure of Bizen, a Traditional Japanese Stoneware, as a Function of Oxygen Partial Pressure

The effects of oxygen partial pressure during thermal treatment on the color and microstructure of Bizen, a traditional Japanese stoneware, were studied through model experiments using clay pellets covered lightly with rice straw as a coloring assistant. When heated in flowing nitrogen, the model pellet turned blackish owing to the formation of α-Fe particles coated with graphite. However, schreibersite (Fe₃P), which is also blackish, was formed specifically on the pellet surface in direct contact with the straw. The rice straw seems to have generated a strongly reducing atmosphere, strong enough for the metallization to α-Fe, and also to have provided phosphorus through contact. When oxygen content in the surrounding gas atmosphere was raised to N₂/O₂=99/1, the pellet surface turned yellowish brown because the main coloring material was Fe³⁺-containing mullite. At oxygen contents of N₂/O₂=98/2 or more, the formation of hematite (α-Fe₂O₃) pushed the color to deep red.     

MANOVA for large hypothesis degrees of freedom under non-normality

In this paper asymptotic distributions of the three commonly used multivariate test statistics, viz.: Likelihood Ratio, Lawley–Hotelling and Bartlett–Nanda–Pillai statistics, are studied for one-way MANOVA hypothesis when the responses are non-normal and the hypothesis degrees of freedom is large. The null as well as the non-null distributions are derived for the balanced as well as unbalanced cases. The results show that these statistics have asymptotic normal distributions. A simulation study reveals the approximations are quite good for number of treatments as small as 15 in the null case. Hence, the results can be applied in real life situation where the assumption of multivariate normality is not tenable. Such situations arise, for example, in agricultural screening trials where large number of cultivars are compared with few replications per cultivar.      

A development of easy-to-use tool for fault detection and diagnosis in building air-conditioning systems

There are many reports about faulty status in building air-conditioning systems recently. It becomes difficult to keep indoor air temperature appropriately as faults occur, and the faults cause waste of building energy consumption. The model-based fault detection and diagnosis (FDD) methods have been researched for specific parts of air-conditioning system such as chillers, coils, variable air volume units (VAV units), etc. It needs, however, much time and labor to monitor and check every single part because we cannot predict where and when the faults occur. The purpose of this study is to examine indoor air temperature changes and energy consumption increase when faults occur and to develop an easy-to-use FDD tool that helps to find out the faulty place through the whole building air-conditioning system. And then, we treat the reliability of the proposed FDD tool and effectiveness to control of indoor environment deterioration and energy consumption increase by the tool is evaluated based on building air-conditioning system simulation in this paper.