A Fault-Tolerant Control Strategy for Three-level Neutral-Point Clamped (NPC) Inverter

When the open-circuit fault occurs on neutral-point clamped (NPC) inverters, it can cause the distortion of output currents, excessively large fluctuation of output voltages, and unbalanced neutral-point potential. Currently, several existing fault diagnosis methods are able to identify the fault types, but they are unable to identify the switching devices where the open-circuit faults occur. Furthermore, even if the open-circuit faults can be identified, the implications caused by open-circuit faults need to be further addressed. This thesis is focused on diagnosing the open-circuit faults and mitigating the problems caused by these faults. An effective fault diagnosis method is proposed in his study to identify the switching devices where the open-circuit faults occur. The characteristics of different distorted currents are firstly analyzed. By normalizing the sampling currents, calculating the average currents and comparing them with thresholds, different faulty switching devices can all be identified. To address the issues caused by these faults, a fault-tolerant control strategy is proposed. By replacing the impossible space vectors caused by these faults with other vectors which can generate the same output voltages, the problems of distortion of output currents and excessively large fluctuation of output voltages can be solved. But the excessively large difference of neutral-point potential still exists. To address the above issue, a model predictive control strategy is proposed to solve the problem of excessively large difference of neutral-point potential. A cost function is built to track the reference vector and suppress the difference of neutral-point potential. The Lagrange function is used to solve the action times of different space vectors. Furthermore, it is shown that when the neutral-point potential is initially unbalanced, the developed strategy is still able to make the potential balanced and greatly reduce its fluctuation

N-[2-Chloro-6-(4-chloro-6-methoxy­pyrimidin-2-ylsulfan­yl)benz­yl]-3,4-dimethyl­aniline

In the title mol­ecule, C20H19Cl2N3OS, the dihedral angle between the two benzene rings is 79.3 (7)°. The 4-chloro-6-methoxy­pyrimidine group is rotationally disordered over two sites by approximately 180°, the ratio of the refined occupancies being 0.6772 (15):0.3228 (15). Both disorder components of disorder are involved in intra­molecular N—H⋯N hydrogen bonds

Model Checking Temporal Logic Formulas Using Sticker Automata

As an important complex problem, the temporal logic model checking problem is still far from being fully resolved under the circumstance of DNA computing, especially Computation Tree Logic (CTL), Interval Temporal Logic (ITL), and Projection Temporal Logic (PTL), because there is still a lack of approaches for DNA model checking. To address this challenge, a model checking method is proposed for checking the basic formulas in the above three temporal logic types with DNA molecules. First, one-type single-stranded DNA molecules are employed to encode the Finite State Automaton (FSA) model of the given basic formula so that a sticker automaton is obtained. On the other hand, other single-stranded DNA molecules are employed to encode the given system model so that the input strings of the sticker automaton are obtained. Next, a series of biochemical reactions are conducted between the above two types of single-stranded DNA molecules. It can then be decided whether the system satisfies the formula or not. As a result, we have developed a DNA-based approach for checking all the basic formulas of CTL, ITL, and PTL. The simulated results demonstrate the effectiveness of the new method

VALUE CREATION THROUGH INTER-ORGANIZATIONAL SYSTEMS (IOS): FROM GOVERNANCE PROCESS VIEW

In this study, we seek to reveal the mechanism of value creation between firms and their partners in B2B context. An integrated conceptual model is constructed grounded in the co-creation theory and the process view, which proposes the interaction between relational assets, IOS support and governance process, as well as their impacts on co-created value. It differs from previous studies by highlighting the mediating effect of governance on value creation. Using a sample of 181 collected from China, our analysis indicates the contribution of governance to co-created value, which is generated through IOS and relational assets. In fact, the IOS support and relational assets alone don’t hold the answer to value co-creation, but they affect the mediating process and enable governance to create value. Especially, the IOS could accommodate the use of relational assets and significantly affect governance process, which is found to be fundamental in value creation. While commodity-like resources have diminishing value in co-creation, governance process with causal ambiguity, social complexity and organizational interconnectedness, becomes the main source of co-created value. Overall, our research sheds light on the key drivers of value co-creation, and provides insights to their impacts on value creation

Research on shear history effect of okra mucilage\u27s viscosity

Background: Okra known in many English-speaking countries as ladies\u27 fingers or ochro, is a flowering plant in the mallow family and contains soluble fibers from the stems of itself. Because of these soluble fibers, it will make the okra-water mixed liquid become thick and viscous, which is the aqueous phase called mucilage. As we all know, okra is one of the healthy vegetables, it has a variety of uses and functions in pharmacology, food industry or biomedical applications. In the previous rheological research, a low-yield mucilage was described obtained via aqueous extraction of okra fruit, named ‘okra mucilage F’. It is a water-soluble, 1.7-million-molecular-weight glycoprotein which produces viscous, shear-thinning, and viscoelastic solutions in water. Some reports showed hot buffer soluble solids solutions are mainly elastic, while chelating agent soluble solids ones are primarily viscous. Because the okra extraction protocols affected the molecular parameters as well as rheological properties of isolates. The mucilage of okra showed very high extensional viscosity, which was two or three orders of magnitude higher than the shear viscosity. And the okra mucilage represented the transition from the shear thinning to the plateau zone approximately at the low shear rate. Objective: However, the previous research did not give a clear view on the shear history effect whether having an influence on the okra mucilage rheological properties. In my study, a rheological experiment was set up to discuss these issues. In order to point out the changed rheological properties when okra mucilage was flowing after high shear stress and long sheared time. Trying to find out what would happen when it was dumped into a narrow tube, so as to give predictability if trying to be dumped into the liver. Method: Okra pods were brought from the local market. It was cleaned by pipe water in order to get rid of the dirt on their skins. Then the okra pods’ seeds were removed and the skins were sliced. After that, the pieces would be store in the pure water at a fixed weight ratio. The mixed solution would be preserved in the refrigerator for a while. The impurity-free okra mucilage was collected by using a combination of weave mesh. The PEO15 solution and jute mucilage were also modulated as a control group. The shear history effect was finished by flowing through a narrow needle with a group of devices. Results: At this stage of my experiments, a changed shear viscosity on okra mucilage after high shear stress treatment was observed. All these three solutions showed shear thinning when they were sheared. In the experiment, the okra mucilage viscosity is sensitively changed after the high strain rate comparing with the PEO15 solution and jute mucilage. At low shear rate (from 0.1S⁻¹ to 100S⁻¹), the viscosity values almost do not change after the high shear stress impact. However, the okra mucilage which was highly pre-sheared by the narrow needle treatment would be decreased 20%-40% at a high shear rate (from 100S⁻¹ to 1000S⁻¹). Moreover, the transaction point around 50～60S⁻¹ was found in one okra mucilage. And the okra mucilage was influenced by the shear history effect when the shear strain rate must be over the transaction point as a limit. Conclusion: Overall, okra mucilage is a very interesting complex fluid. The okra extract structure in the mucilage is changing not only arranged by the rising shear rate but also caused by the shear history effect. In addition, findings suggest that the application of shear history effect irreversibly changes the microstructure of the okra mucilage, and consequently their flow properties. These effects result in that the large soluble okra protein turn into many small crops when the shear stress break the structure as the shear rate researched over transaction point. Moreover, it hints the okra mucilage will flow more and more easily in the microchannel when the flow has been started.首都大学東京, 2019-03-25, 修士（工学）首都大学東