In the conventional inventory policy, the normal distribution approximates the real demand distribution. It is, however, not adequate since the real distribution has distortion. We have proposed an optimal inventory policy based on new demand model with the third order Gram-Charlier series expansion. The new demand model is an approximate normal distribution with the third cumulant. Simulation results show that the proposed method decreases the excess inventory and cost as compared with those of the conventional method.
The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under the thermal condition controlled by electric heaters and a gas burner with a thermal diffuser, the authors measure the inside-temperature profile and the hydrogen-molecule ratio (concentration) RH2, together with the molecule ratios RCH4, RCO and RCO2 of other main gas components such as CH4, CO and CO2, respectively. Besides, the authors conduct numerical simulations based on a thermal-equilibrium theory, in addition to experiments. As a result, the authors successfully achieve suitable inside-temperature profiles. And, the effects of the liquid-hourly-space velocity LHSV upon RH2, RCH4, RCO and RCO2 are shown, experimentally. For LHSV ≤ 1, the experimental results agree well with the thermal equilibrium theory. This is in consistent with high conversion ratio XC12H26 ≳ 80%. Furthermore, the authors reveal the effects of the temperature T inside the reactor upon the molecule ratios, comparing with the thermal-equilibrium theory.
In this paper, we propose a coreless axial gap flux resonant induction motor that utilizes properties of magnetic resonant coupling. The stator and rotor cores of the motor are made with reinforced plastic fiber. Preliminary attempts to study the characteristics of the motor is achieved using an equivalent analysis model through a complete 3-D finite element analysis (FEA). The analysis model has four sets of rectangular-shaped coils, and uniform current density is considered in these rectangular-shaped coils. Evaluations are conducted, and design considerations for these categories of motors are established in this paper. The configuration of the machine constitutes a new domain with largely unstudied potential. Furthermore, the lightweight advantage of these machines makes them a potential candidate for very lightweight applications.
There is a severe labor shortage due to the aging population, and there is an increasing demand for autonomous mobile robots such as delivery robots. These robots operate in the same space as pedestrians, so encounters and overtaking with pedestrians occur. In such cases, the robot can achieve safe and efficient path planning for both the robot itself and pedestrians by recognizing pedestrians as distinct from other obstacles. Therefore, this study aims to propose a pedestrian detection model and evaluate its performance. The sensor used in this paper is a 3D LIDAR, and pedestrian classification is conducted using a machine-learning technique: "Random Forest". The"KITTI" dataset was utilized for model training and simulation. The evaluation of the proposed model showed an accuracy of approximately 98% in cluster-level tests.
A decision model stemmed from Bayesian theorem is proposed to describe the process of decision making for job sequence in manufacturing system. The construction of feature vector is firstly discussed with respect to the manufacturing system’s characteristic. Then a non-parametric model is employed to deal with general distribution for decision acquisition, where a binary division methodology is developed to limit the size of non-parametric model, including elimination of irrelevant features. At last, a PCB manufacturing system is given to demonstrate the efficiency of the model.
A powered exoskeleton is attracting attention to tackle the declining birthrate and aging population. One of the important factors of a powered exoskeleton is back-drivability. Safety can be ensured by improving back-drivability, and we proposed a powered exoskeleton that applies highly back-drivable reduction gearboxes at a high reduction ratio, called bilateral drive gear. The total gear ratio of the proposed exoskeleton is 155.23:1, and the wearer's torque can be estimated without a torque sensor. This paper proposed motion intention prediction using LSTM and examined each model's performance by changing the number of LSTM layers, unit size, and input data. Finally, the experiment was conducted, and 96.12 % prediction accuracy was realized, and the worst delay time for prediction was 305 ms.
The authors develop a small and simple steam-reforming reactor in a home-use size for n-dodecane as a heavy-hydrocarbons fuel. Under such a well-controlled condition by a thermal diffuser as the reactor satisfies two target-temperature criteria, the authors measure the inside-temperature profile and the hydrogen molar fraction (concentration) CH2, together with the molar fractions CCH4, CCO and CCO2 of other main gass components such as CH4, CO and CO2, respectively, using a gas chromatograph. In addition, the authors conduct theoretical calculations based on the thermal-equilibrium theory, and reveal CH2, CCH4, CCO and CCO2, as well as experiments. As a result, the authors successfully achieve suitable inside-temperature profiles. The steam-reforming reaction becomes more active at the position where temperature T > 800 K. The effects of the steam-to-carbon molar ratio S/C upon CH2, CCH4, CCO and CCO2 are shown, experimentally and theoretically. The experimental results agree well with the theoretical ones. Besides, carbon balance and conversion ratio show high accuracy in experiments.
For safety purposes, cooperative robots are installed with an actuator composed of a low-power servo motor, a reduction gearbox, and a torque sensor. When cooperative robots make contact with humans or the environment, they must detect the contact force with a force sensor, a contact sensor, or a joint torque sensor. Equipping these sensors increases the cost and size of the application, but can be avoided under sufficient backdrivability of the actuator. To this end, we propose a method that maximizes the power transmission efficiency of the 3K planetary reduction gearbox and develop a prototype of the backdrivable reduction gearbox called the bilateral drive gear. For this maximization, the profile shift coefficients and the number of teeth are decided under some conditions. The forwardand backward-driving efficiencies of the prototype gearbox were 89.0% and 85.3%, respectively, and the reverse-drive starting torque was 0.020 N·m. The drive efficiency of the same gearbox with uncorrected teeth is 68.5%. The forward-driving efficiency was 20.5% higher than the nonoptimized one. We confirmed that prototype gearboxes with different gear ratios are easily backdrivable by hand.
