Reflection-grating self-pumped phase conjugation with optical feedback free of input conditions

A reflection-grating self-pumped phase-conjugate mirror is demonstrated with a photorefractive KNbO(3) crystal in a novel ring configuration. The feedback beam in the ring configuration is made to track the input probe beam automatically so that the phase conjugation is sustained without readjustment of the optical feedback loop when the angle or the position of the input probe beam is changed. The tracking feedback is realized by means of a simple three-lens erect imaging system. The angular and the positional acceptances for a tightly focused input beam of 50-μm diameter are Δθ(x). = 55 mrad, Δθ(y), = 67 mrad, and Δ(x) = 2.1 mm, Δ(y) = 4.2 mm, respectively.     

Three-dimensional board-to-board free-space optical interconnects and their application to the prototype multiprocessor system: COSINE-III

A prototype multiprocessor system using three-dimensional board-to-board free-space optical interconnects is constructed for the first time to our knowledge. In the system, 64 processing units form a three-dimensional mesh processor network with the help of bidirectional board-to-board free-space optical interconnects. A theoretical analysis shows that the three-dimensional board-to-board freespace optical interconnects effectively solve common interconnection problems such as wiring congestion, signal delay, and clock skew. The prototype system, COSINE-III, is confirmed to work well as a multiprocessor system. The system is also shown to be easy to extend to a larger and more flexible system.     

3He in 99.5% Porous Aerogel at the Normal-Superfluid Transition

We have used a torsional oscillator to measure the superfluid density and dissipation near the superfluid transition of ³ He in aerogel of 99.5% porosity. We used a new cell (constructed at Penn State) for which the aerogel was grown in the pores of a 100 m silver sinter. The cell was tested with ⁴ He and showed no signs of the second-sound resonances that have interfered with previous torsional oscillator measurements. The measurements with ³ He, presented here, were taken at pressures of 1.34 and 4.13 bars. We observed values of _s / in the T 0 limit of 0.05 and 0.14 respectively. Our measurements show an increase in the dissipation on warming through T _c . This series of measurements is ongoing and temperature sweeps at various pressures are planned.     

An approximation algorithm dependent on edge-coloring number for minimum maximal matching problem

We consider the minimum maximal matching problem, which is NP-hard (Yannakakis and Gavril (1980) [18]). Given an unweighted simple graph G=(V,E), the problem seeks to find a maximal matching of minimum cardinality. It was unknown whether there exists a non-trivial approximation algorithm whose approximation ratio is less than 2 for any simple graph. Recently, Z. Gotthilf et al. (2008) [5] presented a -approximation algorithm, where c is an arbitrary constant.In this paper, we present a -approximation algorithm based on an LP relaxation, where χ^′(G) is the edge-coloring number of G. Our algorithm is the first non-trivial approximation algorithm whose approximation ratio is independent of |V|. Moreover, it is known that the minimum maximal matching problem is equivalent to the edge dominating set problem. Therefore, the edge dominating set problem is also -approximable. From edge-coloring theory, the approximation ratio of our algorithm is , where Δ(G) represents the maximum degree of G. In our algorithm, an LP formulation for the edge dominating set problem is used. Fujito and Nagamochi (2002) [4] showed the integrality gap of the LP formulation for bipartite graphs is at least . Moreover, χ^′(G) is Δ(G) for bipartite graphs. Thus, as far as an approximation algorithm for the minimum maximal matching problem uses the LP formulation, we believe our result is the best possible.     

A proteome analysis of the dorsolateral prefrontal cortex in human alcoholic patients

Alcoholic patients commonly experience cognitive decline. It is postulated that cognitive dysfunction is caused by an alcohol-induced region-selective brain damage, particularly to the prefrontal region, and grey and white matter may be affected differently. We used a proteomics-based approach to compare protein expression profiles of the dorsolateral prefrontal cortex (Brodmann area 9 (BA9)) from human alcoholic and healthy control brains. Changes in the relative expression of 110 protein 'spots' were identified in the BA9 grey matter, of which 54 were identified as 44 different proteins. In our recent article, 60 protein spots were differentially expressed in the BA9 white matter and 18 of these were identified (Alexander-Kaufman, K., James, G., Sheedy, D., Harper, C., Matsumoto, I., Mol. Psychiatry 2006, 11, 56-65). Additional BA9 white matter proteins are identified here and discussed in conjunction to our grey matter results. Thiamine-dependent enzymes transketolase and pyruvate dehydrogenase (E1β ubunit) were among the proteins identified. To our knowledge, this is the first time a disruption in thiamine-dependent enzymes has been demonstrated in the brains of 'neurologically uncomplicated' alcoholics. By identifying protein expression changes in prefrontal grey and white matter separately, hypotheses may draw upon more mechanistic explanations as to how alcoholism causes the structural alterations associated with alcohol-related brain damage and cognitive dysfunction.     

Analysis of accelerated creep under constant sustaining load for austenitic stainless steels

The effect of stress on creep rate of austenitic stainless steels of type 347 and 316 was studied by applying the differential test technique. It was found that the creep rate could be expressed as follows, whereB ₁ is a material constant depending on temperature,a ₁ anda _o are constants, and σ is the real stress. Considering the increase in real stress during creep process due to void formation and to the decrease in cross sectional area of the specimen, integrating the above equation yields the following creep curve, 1 $$ \in = \in _m + \frac{1}{{n_o \left( {c_o + 1} \right)}}ln\frac{1}{{1 - n_o \left( {c_o + 1} \right) \in _m (t - t_{_m } )}}$$ where ∈ is the creep strain at a given time (t), ∈_m is the minimum creep rate, ∈_m andt _m are the strain and time, respectively, at the minimum creep rate,n _o is a constant, andc _o is the material constant relating to the void formation. This equation agrees very well with the experimental creep curve.     

Study on high performance ice slurry formed by cooling emulsion in ice storage (discussion on adaptability of emulsion to thermal storage material)

This study focuses on an emulsion as a new thermal storage material for ice storage. Two types of emulsions were formed using an oil–water mixture with a small amount of additive. A silicone, light and lump oils were used. The water contents of the emulsions were 70, 80 and 90%. The additive was an amino group modified silicone oil. No depression of freezing point was observed for the emulsions because of their hydrophobic properties. In order to determine the structure of the emulsions, their electrical resistances were measured. Moreover, components of the liquids separating from the emulsions were analyzed. The results indicated that one emulsion was a W/O type emulsion, while the other was an O/W type. Finally, adaptability of the two emulsions to ice storage was discussed, it was concluded that a high performance ice slurry could be formed by the W/O type emulsion.     

Analysis and experimental validation of force bandwidth for force control

Controlling robots in contact with the environment is an important problem in industry applications. In the conventional force control, much research has paid attention to develop novel force control systems and implemented force sensors to detect external force. This paper shows that narrow bandwidth of force sensor has a big influence on the force control system. Generally, to solve the instability in force control, the velocity feedback gain is enlarged. The system becomes unstable with small velocity feedback gain, and robot's response becomes slow with large one. Inasmuch as there is a tradeoff between the stability and the response, it is considered that force control by robots is difficult. This paper proposes a force control system with disturbance observer. It is possible to obtain the force information with wide bandwidth by using the disturbance observer. This paper shows that bandwidth of force sensing is very important for contact motion control. By using the wide bandwidth of force sensing, both stability and response are improved. Furthermore, force control is attainable by the construction of the easiest force control architecture. Therefore, the ideal zero-stiffness-force control is attained. The numerical and experimental results show viability of the proposed method.     

Study on Pb-Bi natural circulation phenomena

For the development of 45w%Pb-55w%Bi cooled direct contact boiling water small fast reactor (PBWFR), experimental study on Pb-Bi-water direct contact boiling two-phase flow has been performed using Pb-Bi-water direct contact boiling two-phase flow loop. For stable start-up of the boiling flow operation, Pb-Bi single-phase natural circulation must be realized in a Pb-Bi flow system of the loop before water injection into Pb-Bi. The Pb-Bi flow system consists of a four-heater-pin bundle, a chimney, an upper plenum, a level meter tank, a cooler, and an electromagnetic flow meter. A stable Pb-Bi single-phase natural circulation was realized in the range of flow rate from 1.5 l/min to 4.8 l/min by heating Pb-Bi in the heater-pin bundle with a power up to 7.7 kW. The inlet and outlet temperatures of the heater bundle were in the ranges from 243°C to 278°C, and from 251°C to 278°C, respectively. The natural circulation flow was simulated analytically using one-dimensional flow model including frictional, form and drag forces. Total hydraulic head through the loop were calculated from Pb-Bi densities at measured Pb-Bi temperatures in the loop. It was found that the calculated flow rate agreed well with the measured ones, which indicated the validity of the analytical models.