Fast-sweeping Langmuir probes: what happens to the I-V trace when sweeping frequency is higher than the ion plasma frequency?

Limited particle transit time is one of several limiting factors which determines the maximum temporal resolution of a Langmuir probe. In this work, we have revisited known fast sweep Langmuir probe techniques in a uniform, quiescent multi-dipole confined hot cathode discharge with two operation scenarios: one in which the probe sweeping frequency fsweep is much lower than the ion plasma frequency fpi, another one where fsweep is much greater than fpi, respectively. This allows the investigation of the effect of limited ion-motion on I-V traces. Serious distortions of I-V traces at high frequencies, previously claimed to be ion-motion limitation effect, was not found in the degree previously claimed unless shunt resistance is sufficiently high, despite achieving a ratio of ~ 3 between the probe sweeping frequency and the ion plasma frequency. On the other hand, evidences of sheath capacitance on the I-V trace have been observed. Distortions of I-V traces qualitatively agrees with predictions of sheath capacitance response to the sweeping voltage. Additionally, techniques in fast sweep Langmuir probe are briefly discussed. The comparison between a High-speed dual Langmuir probe (HDLP) and the single probe setup shows that the capacitive response can be removed via subtracting a leakage current for the single probe setup almost as effective as using an HDLP setup, but the HDLP setup does remain advantageous in its facilitation of better recovery of weak current signal common in low plasma density situations.

Energy-saving design and implementation in metro weak current systems: a case study of the Kunming metro system

With the accelerated urbanization in China, along with the growing scale of the metro transportation network, the energy consumption of metro systems continues to increase. To face the tough challenge of climate change, China has put forward the goal of peak carbon emissions by 2030 and achieving carbon neutrality by 2060. Energy consumption has become a serious burden for metro operation companies, since 10.2% of the total operational budgets is spent on electricity. Thus the development of methods to realize energy saving and emission reduction has become a major challenge for metros. In this study we conduct an in-depth research and analysis on metro energy load classification and energy management, focusing in particular on the design and usage of power supply systems for metro weak current electromechanical systems, including tunnel fans, station air conditioners, station escalators, automatic ticketing equipment, screen doors, drainage pumps, sewage pumps, platform doors, communication systems, signals, integrated monitoring systems, automatic ticketing and various lighting equipment and facilities. It is proposed that the five weak current systems, namely platform doors, communication systems, signals, integrated monitoring and automatic fare collection, should adopt a backup power supply. In order to ensure the reliable operation of all weak current systems in the station, the traditional decentralized power supply mode is changed to a centralized power supply and uninterruptible power supply (UPS) (1 + 1) parallel double-bus system. At the same time, combined with the data on equipment quantity, station passenger flow and station building floorage, the Boruta algorithm is used to filter out the equipment related to station weak current energy consumption, and a principal component analysis (PCA) algorithm is used to further reduce the dimensions of the filtered features to reduce the algorithm overhead of the subsequent quota analysis model. The XGBoost algorithm is used to establish a prediction model for station weak current system energy consumption. Analysis shows that there is a strong correlation between the energy consumption quota and the equipment quantity as well as station building floorage. By setting different metering instruments for power supply circuits, the main energy consumption data are collected to meet the requirements for graded metering of metro energy consumption, and then the energy consumption quota for the station weak current system is reasonably predicted. By adding metering instruments to the power supply circuits of different areas and equipment, the energy consumption of the weak current system can be measured and monitored in different grades. The combination of the energy management platform and energy consumption quota provides the basis for energy management of each energy-consuming unit, and ultimately realizes energy saving and reduced consumption.

Ocular direct current stimulation affects retinal ganglion cells

Ocular current stimulation (oCS) with weak current intensities (a few mA) has shown positive effects on retinal nerve cells, which indicates that neurodegenerative ocular diseases could be treated with current stimulation of the eye. During oCS, a significant polarity-independent reduction in the characteristic P50 amplitude of a pattern-reversal electroretinogram was found, while no current stimulation effect was found for a full field electroretinogram (ffERG). The ffERG data indicated a trend for a polarity-dependent influence during oCS on the photopic negative response (PhNR) wave, which represents the sum activity of the retinal ganglion cells. Therefore, an ffERG with adjusted parameters for the standardized measurement of the PhNR wave was combined with simultaneous oCS to study the potential effects of direct oCS on cumulative ganglion cell activity. Compared with that measured before oCS, the PhNR amplitude in the cathodal group increased significantly during current stimulation, while in the anodal and sham groups, no effect was visible (α = 0.05, pcathodal = 0.006*). Furthermore, repeated-measures ANOVA revealed a significant difference in PhNR amplitude between the anodal and cathodal groups as well as between the cathodal and sham groups (p* ≤ 0.0167, pcathodal − anodal = 0.002*, pcathodal − sham = 0.011*).

The Characteristics of Kasiro Shale and Its Implication to Oil Shale Identification at The Batang Asai, Sarolangun, Jambi

The necessity of oil and natural gas from fossil energy sources in Indonesia is increasing over time, whereas oil and gas reserves generated from conventional reservoirs are decreasing. To anticipate gas shortages, exploration of unconventional resources is needed. The main focus of the rock formation in this research is the Tertiary Miocene Kasiro Formation. This formation is dominated by Shale and Claystone. Shale characteristic from the megascopic aspect of Tertiary Miocene Kasiro Formation in the research area have fissile structure with soft to hard in hardness scale of shale. Shale characteristic from microscopic aspect based on petrography, SEM (Scanning Electron Magnetic) and XRD (X-Ray Diffraction) show illite as main clay mineral. Other clay minerals such as montmorilonite and kaolinite also can be found as well as some important mineral like quartz, chlorite, biotite, alunite and diaspore. Shale diagenesis rate of the Tertiary Miocene Kasiro Formation is defined based on the presence of some clay mineral like illite, kaolinite and montmorillonite. Based on the result of SEM and XRD analyses, the shale diagenesis in the research area can be classified as early mesodiagenesis. The diagenesis rate also can show that oil maturity in the Kasiro shale can be classified as immature to semi mature. Based on the shale characteristic, the Kasiro shale was deposited in a weak current mechanism and based on the presence of alginite, the shale was deposited within lacustrine environment. The lacustrine environment have a characteristic of low oxygen rate that can be seen with the presence of mollusk fossil such as viviparous that indicating a fresh water and weak current enviroment.

Response of methanogen communities to the elevation of cathode potentials in bioelectrochemical reactors amended with magnetite

Electromethanogenesis refers to the process where methanogens utilize current for the reduction of CO 2 to CH 4 . Setting low cathode potentials is essential for this process. In this study, we test if magnetite, an iron oxide mineral widespread in the environment, can facilitate the adaption of methanogen communities to the elevation of cathode potentials in electrochemical reactors. Two-chamber electrochemical reactors were constructed with inoculants obtained from paddy field soil. We elevated cathode potentials stepwise from the initial -0.6 V vs the standard hydrogen electrode (SHE) to -0.5 V and then to -0.4 V over the 130 days acclimation. Only weak current consumption and CH 4 production were observed in the bioreactors without magnetite. But significant current consumption and CH 4 production were recorded in the magnetite bioreactors. The robustness of electro-activity of the magnetite bioreactors was not affected by the elevation of cathode potentials from -0.6 V to -0.4 V. But, the current consumption and CH 4 production were halted in the bioreactors without magnetite when the cathode potentials were elevated to -0.4 V. Methanogens related to Methanospirillum were enriched on the cathode surfaces of magnetite bioreactors at -0.4 V, while Methanosarcina relatively dominated in the bioreactors without magnetite. Methanobacterium also increased in the magnetite bioreactors but stayed off electrodes at -0.4 V. Apparently, the magnetite greatly facilitates the development of biocathodes, and it appears that with the aid of magnetite, Methanospirillum spp. can adapt to the high cathode potentials performing efficient electromethanogenesis. IMPORTANCE Converting CO 2 to CH 4 through bioelectrochemistry is a promising approach to the development of green energy biotechnology. This process however requires low cathode potentials, which takes cost. In this study, we test if magnetite, a conductive iron mineral, can facilitate the adaption of methanogens to the elevation of cathode potentials. In the two-chamber reactors constructed by using inoculants obtained from paddy field soil, biocathodes were firmly developed in the presence of magnetite, whereas only weak activities in CH 4 production and current consumption were observed in the bioreactors without magnetite. The elevation of cathode potentials did not affect the robustness of electro-activity of the magnetite bioreactors over the 130 days acclimation. Methanospirillum were identified as the key methanogens associated with the cathode surfaces during the operation at high potentials. The findings reported in this study shed new light on the adaption of methanogen communities to the elevated cathode potentials in the presence of magnetite.

Mudrock Microstructure: A Technique for Distinguishing between Deep-Water Fine-Grained Sediments

Distinguishing among deep-water sedimentary facies has been a difficult task. This is possibly due to the process continuum in deep water, in which sediments occur in complex associations. The lack of definite sedimentological features among the different facies between hemipelagites and contourites presented a great challenge. In this study, we present detailed mudrock characteristics of the three main deep-water facies based on sedimentological characteristics, laser diffraction granulometry, high-resolution, large area scanning electron microscopy (SEM), and the synchrotron X-ray diffraction technique. Our results show that the deep-water microstructure is mainly process controlled, and that the controlling factor on their grain size is much more complex than previously envisaged. Retarding current velocity, as well as the lower carrying capacity of the current, has an impact on the mean size and sorting for the contourite and turbidite facies, whereas hemipelagite grain size is impacted by the natural heterogeneity of the system caused by bioturbation. Based on the microfabric analysis, there is a disparate pattern observed among the sedimentary facies; turbidites are generally bedding parallel due to strong currents resulting in shear flow, contourites are random to semi-random as they are impacted by a weak current, while hemipelagites are random to oblique since they are impacted by bioturbation.