Low-threshold operation of 1.5?m buried-heterostructure DFB lasers grown entirely by low-pressure MOVPE

Buried-heterostructure (BH) distributed feedback (DFB) lasers have been fabricated by a three-step low-pressure MOVPE process. The CW threshold currents were as low as 15mA and a high differential efficiency of 0.21 W/A was obtained. The laser operated in a stable single longitudinal mode over a wide range of driving currents and under highspeed direct modulation.     

Spectral characteristics of a DFB laser under high-speed direct modulation

Characteristics of a DFB laser under high-speed direct modulation are studied with an emphasis on the spectral analysis. A stable single-longitudinal-mode oscillation was confirmed up to 8.4 GHz direct modulation. The possibility of reducing the frequency chirping by device parameter optimisation is predicted on the basis of the experimental results obtained.     

Propofol-air-oxygen anesthesia reduces the incidence of sore throat after laryngeal mask anesthesia

We investigated the effects of the presence or absence of N2O in propofol anesthesia using a laryngeal mask on the incidence of postoperative sore throat. In the N2O-combined anesthesia group (n = 25), score 0 (no sore throat) was observed in 11 patients; score 1 (slight pain and discomfort that improved on the next day of operation) in 9; and score 2 (persistent pain on the next day) in 5. In the non-N2O-combined anesthesia group (n = 25), score 0 was observed in 21 patients, score 1 in 3; and score 2 in 1, showing a significantly lower incidence of sore throat and milder sore throat than in the N2O-combined anesthesia group. These results suggest that propofol anesthesia using a laryngeal mask not combined with N2O reduces the incidence of postoperative sore throat.     

Development of robot teaching support devices to automate deburring and finishing works in casting

Concerning robot teaching, an online teaching method has conventionally been carried out by skilled workers using a teaching pendant. However, the teaching pendant is different with every robot manufacture and requires a large number of man-hours to assign a large number of points in defining the tool path for deburring. In recent years, use of an offline teaching method that utililises a three-dimensional robot simulation system has begun to spread, however, this is not necessarily easy to introduce in medium- and small-sized businesses. Thus two kinds of teaching support devices were developed from actual workpieces and deburring tools to prepare the tool path, considering the volume of investment for equipment and training of operators. One is a three-wire type teaching support device, and the other an arm type one. The former consists of tension wires supported at three points like a kite, and the latter consists of two arms and six connecting axes. Each device can measure the position and posture of a dummy tool in the devices coordinates. From the experiments, the arm-type teaching support device shows enough precision capability as a teaching support device, as opposed to the three-wire type teaching support device, which is cost-effective.     

Experimental fluid dynamics of particles in a dielectric barrier discharge plasma-enhanced spouted bed

This study proposed the fluidized particles with dielectric barrier discharge (DBD) plasma in a slot-rectangular divergent-base spouted bed and focused on the dynamics of solid particles with the plasma irradiation. Two bed materials (Polypropylene (PP) particles and Polyamide (PA) particles) with same diameter (3 mm) were fluidized in this study. Fluidization parameters included gas velocity (7.4–14.9 m/s), particle amount (100–500), and plasma parameter (apply voltage, 0 and 7 kV) as the applied voltage were investigated here. Particle velocity profiles were analyzed through the methods of particle image velocimetry (PIV) and particle tracking velocimetry (PTV). Results show that the particle velocity was increased with the plasma irradiation, mainly by the enhancement in the vertical direction. The location of the highest particle velocity area related to the fluidization behavior of particles. With the increase of superficial gas velocity, the location of the highest particle velocity area raised along the central line but not reached the top of the solid bed. While the electron temperature of Ar plasma decreased with the addition of particles. Two electric fields (external electric field and surface charge electric field) presenting in the system were assumed to give the reason for the changes of the particle fluid dynamics.     

Drying of Dielectric Resin Coatings in the Presence of Polycondensation

Drying of dielectric resin coatings is accompanied simultaneously by evaporation of multicomponent solvents and polycondensation from monomers. The characteristic of the drying is studied experimentally. As a test sample, a vanish consisting of trimellitic acid anhydride and 4.4¹-diphenylmethane diisocyanate dissolved in the mixture of N-methylpyrrolidone and xylene is coated on an aluminum pan. The sample is subjected in drying in two types of dryers: hot air heating and radiation heating. The constant drying rate period is not observed in any run. The maximum drying rate of the sample is lower than the evaporation rate from the solvent layer with no resin. There are remarkable fluctuations in the drying rate in the decreasing drying rate period. The fluctuations are caused by bubble formation. The progress of the reaction can be followed by IR spectroscopic analysis. From these results it is suggested that removal of the solvent and the product is inhibited by the formation of a polymer skin on the surface and it makes control of drying difficult.     

Impurity-induced disordering of AIGalnAs quantum wells by low temperature Zn diffusion

We investigated impurity-induced disordering (IID) in AIGalnAs multi-quantum wells (MQWs) on InP substrate by Zn diffusion under low temperature conditions. Blue-shift of band-gap energy of lattice-matched AIGalnAs MQW on InP strongly depended on the temperature of Zn diffusion. The lattice-matched MQW was not completely disordered below 500°C. On the other hand, photoluminescence spectra from compressively strained AIGalnAs MQW, after disordering was independent of the temperature of Zn diffusion. Considerable disordering was observed in the strained MQW, which was saturated even at the low temperature of 400°C. The measured hole concentration of the Zn diffused layer at 400°C was as low as 3 × l0¹⁸cm⁻³ The IID lasers were also fabricated and characterized. No significant increase in the optical loss due to the Zn diffusion was observed in these lasers. On leave from Toshiba Co., Japan.     

Auction-based production planning considering operators' skill criterion

With the penetration of the IoT and data science, new manufacturing initiatives are accelerating. However, conventional approaches have emphasized the use of machine-based data. A need exists to realize more productive work styles considering the abilities and physical condition of operators. In this paper, we propose a production planning method to allocate machines and operators with different skill level optimally. After formulating a combinatorial auction mechanism, developing a schedule that minimizes the total production cost, we verify that the proposed method can realize human-centered production planning by combining the schedules with different evaluation indices.