Statistical Properties of a Generalized Threshold Network Model

The threshold network model is a type of finite random graph. In this paper, we introduce a generalized threshold network model. A pair of vertices with random weights is connected by an edge when real-valued functions of the pair of weights belong to given Borel sets. We extend several known limit theorems for the number of prescribed subgraphs and prove a uniform strong law of large numbers. We also prove two limit theorems for the local and global clustering coefficients.     

Prototype of Low Thermal Expansion Materials: Fabrication of Mesoporous Silica/Polymer Composites with Densely Filled Polymer inside Mesopore Space

A prototype of novel low thermal expansion materials using mesoporous silica particles is demonstrated. Mesoporous silica/polymer composites with densely filled polymer inside the mesopore space are fabricated by mechanically mixing both organically modified mesoporous silica and epoxy polymer. The mesopores are easily penetrated by polymers as a result of the capillary force during the mechanical composite processing. Furthermore, we propose a new model of polymer mobility restriction using mesoporous silica with a large pore space. The robust inorganic frameworks covering the polymer effectively restrict the polymer mobility against thermal energy. As a result, the degree of total thermal expansion of the composites is drastically decreased. From the mass‐normalized thermal mechanical analysis (TMA) charts of various composites with different amounts of mesoporous silica particles, it is observed that the coefficient of thermal expansion (CTE) values gradually increase with an increase of the polymer amount outside the mesopores. It is proven that the CTE values in the range over the glass‐transition temperatures (T_g) are perfectly proportional to the outside polymer amounts. Importantly, the Y‐intercept of the relation equation obtained by a least‐square method is the CTE value and is almost zero. This means that thermal expansion does not occur if no polymers are outside the mesopores. Through such a quantative discussion, we clarify that only the outside polymer affects the thermal expansion of the composites, that is, the embedded polymers inside the mesopores do not expand at all during the thermal treatment.     

Effect of oxygen deficiency on response of CR-39 on board scientific balloons

We should be careful about the effect of oxygen deficiency on polymeric track detectors even at balloon altitude. Results of balloon experiments and calibration experiments in a vacuum chamber at different pressures show that the effect of oxygen deficiency becomes serious at a pressure below 10 hPa.     

Alleviation of thermally induced phase mismatch in CsLiB6O10 crystal by means of temperature-profile compensation

A new mechanism was found to alleviate the thermally induced phase mismatch of nonlinear optical crystals. By cooling CsLiB>(6)O(10) at an elevated crystal temperature with gas, we improved laser conversion efficiency from green (532 nm) to UV (266 nm) 2.3 times compared with that without cooling. In situ observation of the temperature profile on the output surface revealed that such cooling initiates a negative temperature profile that compensates for the positive profile generated from laser absorption. A 10.6-W UV output with excellent stability was generated. The optimum crystal length was substantially extended.