Method of Moments (MoM): Application for Solving Augmented Electric Field Integral Equation (AEFIE)

Surface integral equations (SIEs) are promising candidates for modeling circuits because they reduce degrees of freedom by restricting physical unknowns on the surface, which simplifies complex structures. However, there are still challenges related to achieving stability over a broad frequency band. Specifically, the low frequency breakdown of electrical field integral equation (EFIE) operator is discussed in this work. In order to solve or alleviate this problem, the separation of irrotational and solenoidal current must be accomplished. A proposed method, the Augmented Electrical Field Integral Equation (AEFIE), is intended to separate the current element by introducing charge as another variable and relate irrotational current and the charge vector. Finally, the method of moments (MoM) is applied to solve the integral equation by projecting the current onto RWG basis and performing subspace projections to fill out the integral equation operator matrix. For complicated circuit structure, MoM can be accelerated using the fast multipole algorithm (FMA).Ope

An adaptive fault current limiting control for MMC and its application in DC grid

This paper proposes an adaptive fault current limiting control (AFCLC) for modular multilevel converters (MMC). Without introducing extra current limiting devices, this control scheme enables fast fault current suppression during DC faults. The AFCLC will be triggered automatically once DC faults occur. By adaptively reducing the output DC voltages of MMCs, the fault current can be suppressed. Compared with the existing current limiting methods, the proposed AFCLC has a better performance on fault current limiting, since it only depends on the real-time operating condition and no fault detection delay is imposed. Firstly, the principle of the proposed AFCLC together with the mathematical analysis is disclosed. Then, the sensitivity analysis of the impact of key control parameters on the current limiting effect is investigated. Finally, the effectiveness of AFCLC is demonstrated in a four-terminal HVDC grid test model. The simulation results show that the proposed AFCLC can reduce the interrupted current and energy absorption of a DCCB from 10.39 kA and 38.24 MJ to 4.62 kA and 8.32 MJ, respectively. The simulation results also prove that the AFCLC will not affect the accuracy of the DC fault detection algorithms under DC faults

The 8D05 Parasitism Gene of Meloidogyne incognita Is Required for Successful Infection of Host Roots

Parasitism genes encode effector proteins that are secreted through the stylet of root-knot nematodes to dramatically modify selected plant cells into giant-cells for feeding. The Mi8D05 parasitism gene previously identified was confirmed to encode a novel protein of 382 amino acids that had only one database homolog identified on contig 2374 within the Meloidogyne apla genome. Mi8D05 expression peaked in M. incognita parasitic second-stage juveniles within host roots and its encoded protein was limited to the subventral esophageal gland cells that produce proteins secreted from the stylet. Constitutive expression of Mi8D05 in transformed Arabidopsis thaliana plants induced accelerated shoot growth and early flowering but had no visible effects on root growth. Independent lines of transgenic Arabidopsis that expressed a double-stranded RNA complementary to Mi8D05 in host-derived RNA interference (RNAi) tests had up to 90% reduction in infection by M. incognita compared with wild-type control plants, suggesting that Mi8D05 plays a critical role in parasitism by the root-knot nematode. Yeast two-hybrid experiments confirmed the specific interaction of the Mi8D05 protein with plant aquaporin tonoplast intrinsic protein 2 (TIP2) and provided evidence that the Mi8D05 effector may help regulate solute and water transport within giant-cells to promote the parasitic interaction

Active current-limiting control to handle DC line fault of overhead DC grid

To handle with the DC line faults in a DC grid, this paper proposed an active current-limiting controller for hybrid MMC. With this active current-limiting control strategy, the requirement of interruption current of DCCB will be significantly decreased, and the investment of DC grid will be reduced obviously. Firstly, the control architecture of active current-limiting controller is disclosed. To avoid the overvoltage of submodule capacitors during DC fault, a dynamic limiter for the reference value of the DC current controller is proposed. To decrease the peak of fault current, the feedforward controller of DC voltage is put forward. The decoupling controllability of the AC/DC voltage of hybrid MMC is disclosed. The current-limiting mechanism of the active current-limiting controller is analysis. Then, the validity of the active current-limiting control strategy is verified by RTDS

Impact of strength and proximity of receiving AC systems on cascaded LCC-MMC hybrid HVDC system

The cascaded hybrid LCC-MMC inverter is considered as a feasible option to mitigate the commutation failure problem of conventional LCC-HVDC while maintaining bulk power transmission capability. However, the coupling between different types of converters may result in instability when the inverter integrates with weak AC systems. This paper establishes a small-signal model of the cascaded LCC-MMC inverter based hybrid HVDC system and validates the model against PSCAD/EMTDC. Through eigenvalue analysis, the impact of the strength and proximity of receiving AC systems on the small-signal stability is investigated, and the stable zone of the strength of receiving AC systems is identified. Besides, a supplementary coupling mitigation control is proposed to tackle the instability problem under weak AC systems integration. Both analytical results and time-domain simulations demonstrate the validity of the supplementary control

Study on potential gradient in Ti anodization

Porous oxides or nanotubes are obtained through the anodization of valve metal. However, the mechanism of nanotube growth remains unclear. Traditional field-assisted dissolution (FAD) theory has many limitations, such as its inability to explain the connotation of the three stages in the current–time curve. By placing a container between two electrodes, the ions move around the container in a ring in the present study. The potential gradient during anodization was innovatively changed. Finally, the current–time curve obtained during anodization using the new device is quite different from that obtained using conventional anodizing device. This phenomenon is explained by the electronic current and ionic current theory in this paper

Effect of high-protein vs. high-fat snacks before lunch on glycemic variability in prediabetes: A study protocol for a randomized controlled trial

BackgroundChina has the largest number of patients with Type 2 Diabetes Mellitus (T2DM), and it tends to increasingly grow in the future, putting an enormous burden on disease control and prevention in China. While glycemic variability (GV) came to be an important indicator of blood glucose control in diabetic patients, studies suggested that premeal snacks may help blood glucose control, but there are still some problems to be researched. Therefore, we designed this trial to evaluate which kind of premeal snacks would lead to better effects on GV under two diet patterns in pre-diabetes subjects and to evaluate assessments of acceptability and compliance, behavior, and metabolism changes in individuals will be described.Methods and analysisThe study is a single-center, open-label, multiparallel group, randomized controlled trial. A total of 32 male and female volunteers will be randomized into 4 groups in a single allocated ratio of soy milk (powder) snack, milk (powder) snack, almonds snack, and placebo control with 250 ml of water taken 30 min before lunch, respectively. The study consists of two intervention periods over 11 days. The first intervention period under habitual diet conditions from D3 to D6 (4 days), during which all subjects are asked to maintain their habitual eating and daily activities similar to the run-in period. The second intervention consists of prelunch snacks with standard meals. We will examine both the effect of GV and various metabolic and behavioral outcomes potentially associated with the interventions. At the end of this study, we will assess the acceptability and maintainability of the intervention through interviews.Clinical trial registrationChinese Clinical Trial Registry, identifier ChiCTR2200058935

A mechanical DCCB with re-closure capability and its performance in MMC based DC grid

For the modular multilevel converter (MMC) based DC grids using overhead line transmission, to restore the power transmission quickly, the DC circuit breakers (DCCB) are required to be able to re-close after DC line faults. To meet this requirement, an improved mechanical DCCB topology with re-closure capability is proposed in this paper. It consists of a pre-charged capacitor, an auxiliary capacitor, an oscillation inductor, and anti-parallel thyristors. Firstly, the topology and operating principle of the mechanical DCCB are presented in detail. Then, the general sizing methods associated with the impact of parameters on interruption capability are disclosed. The feasibility of the proposed mechanical DCCB is validated in a stiff DC system. Finally, the transient performance of the DC grid embedding the proposed mechanical DCCBs is investigated under various operating scenarios. The results verify the DC fault interruption and fast automatic re-closure capabilities of the proposed DCCB. It is shown that the mechanical DCCBs can be well applied to the overhead MMC based HVDC grids systems