Basis For Real-time Monitoring Research Articles

Performance improvement of on-chip mid-infrared waveguide methane sensor using wavelet denoising and Savitzky-Golay filtering

Due to mode interference and reflection, waveguide gas sensor is prone to generate noise, which affects gas detection performance. In order to improve the performance of waveguide methane (CH4) sensor, wavelet denoising (WD) and Savitzky-Golay (SG) filtering were combined to process the noisy signal. With the fabricated silicon-on-insulator (SOI) ridge waveguide, a waveguide CH4 sensing system was built, and the absorbance signal was processed by denoising schemes. Experimental results show that compared with the traditional WD scheme, the WD-SG scheme has obvious advantages in suppressing low-frequency random noise and interference noise. Using WD-SG scheme, the signal-to-noise ratio (SNR) of the absorbance signal is increased by 4.95 times. According to the Allan deviation analysis, the 1σ limit of detection (LoD) of the sensor is reduced from 2929 parts per million (ppm) to 397 ppm when the WD-SG scheme is adopted. The sensor shows a fast response time of less than 2.5 s. Our work shows that the WD-SG scheme can effectively improve the SNR and reduce the influence of noise on the waveguide sensor system on the basis of real-time monitoring.

Functional Quantitative and Qualitative Models for Quality Modeling in a Fused Deposition Modeling Process

Additive manufacturing (AM) enables flexible part geometry and functionality, and reduces product development life cycle by direct layer-wise fabrication from CAD files. In the last decade, great achievements are made on AM materials, machines, processes, etc. However, the quality of the AM parts is still questionable for industrial specifications. On the one hand, AM part quality variables can be either quantitative, such as dimensional accuracy, or qualitative, such as binary indicators for voids, missing features, or surface roughness. On the other hand, both offline process setting variables and functional in situ process variables can be measured and modeled with both quantitative and qualitative (QQ) quality response variables. In this paper, the QQ quality response variables are modeled by offline process setting variables and in situ process variables via functional QQ models. The modeling of these in situ process variables provides the basis for real-time monitoring and control for AM processes. Simulation studies and experimental data from a fused deposition modeling process are performed to demonstrate the effectiveness of the proposed method. Note to Practitioners —Additive manufacturing (AM) processes have attracted much attention and showed many advantages over the traditional subtractive manufacturing processes. However, the product quality issues make AM intractable for high-quality parts in industrial applications. This paper aims to address the quality issues by modeling both quantitative quality variables, such as dimensional accuracy, and qualitative quality variables, such as the binary (go/no-go) indicator for surface conditions. Both offline process setting variables and in situ process variables are used in the model as predictors. Such a model is important for systematically quality evaluation of AM parts, and provides the basis for future process monitoring and control. The merits of the proposed method are demonstrated with simulation studies and a case study in a fused deposition modeling process.

Method of Wireless Sensor Network Node Deployment for the Emergency Environment

Incidents could not always be avoided, resulting in significant losses for the state property and people's safety. Effective monitoring of incidents is becoming more and more important. Wireless sensor networks (WSNs) are widely used in environmental monitoring. On the basis of the existing wireless sensor network node deployment model, a network node deployment model was proposed, which was used in the monitoring of unexpected accidents. The model area was divided into the core area and the evacuation area, and different monitoring nodes deployment plans were applied in different areas. The simulation experiment is carried out by MATLAB, and the simulation results of the node coverage are obtained. Results show that the model for the practical application of the node deployment provides an effective deployment plan, as well as offers a strong basis for real-time monitoring and post-accident emergency evacuation.

Study on leakage dissolution around the dam foundation of the Qingju Hydropower Station and its engineering influence on the dam

Leakage dissolution is one of the potential threats to the long-term operating safety of a dam. The aim of this paper is to analyze the characteristics of leakage dissolution around the dam foundation of Qingju Hydropower Station and evaluate its engineering influence based on laboratory testing and in situ monitoring. Comparative analysis of water samples in 20 representative positions shows that the bedrock of the dam foundation has been enduring obvious dissolution under the effects of the groundwater. In situ monitoring data of displacement and leakage during the period from 2005 to 2013 indicates that there has been no excessive deformation, obvious uneven settlement, or concentration leakage in these nine years, and; therefore, the leakage dissolution of the dam foundation has not resulted in critical danger to the safety of dam so far. However, with an annual amount of gypsum dissolution discharged by the drainpipes of about $$ 1.82 \times 10^{5}\,{\rm kg} $$ , long-term leakage dissolution may be hazardous, besides the higher content of SO4 2− than normal in the groundwater of the dam foundation caused by leakage dissolution may invoke some crystal corrosion and decrease the durability of the concrete structures. To guarantee the long-term safety of the dam, implementing grouting is proposed to prevent dissolution or slow down the dissolution rate on the basis of real-time monitoring and feedback.

Determinación de los Límites de Estabilidad Estática de Ángulo del Sistema Nacional Interconectado

La diferencia angular de los voltajes de barra de un sistema eléctrico de potencia (SEP) es una medida directa del estado de congestión del sistema. En este sentido, su continuo monitoreo brinda al operador una señal de alerta de posibles estados de congestión del SEP, cuando las diferencias angulares superan límites de seguridad pre-establecidos (límites de estabilidad estática de ángulo). Con el desarrollo de la tecnología de medición sincrofasorial, el monitoreo de la diferencia angular ha adquirido un nuevo enfoque, puesto que se independiza del estimador de estado, lográndose mayor robustez y rapidez. El operador del Sistema Nacional Interconectado, CENACE, dispone actualmente de un sistema de medición sincrofasorial, administrado por la plataforma WAProtector. Este software dispone de una aplicación que permite el monitoreo de la diferencia angular de voltajes de barra del sistema, usando técnicas de visualización avanzada. Este artículo presenta una introducción a la tecnología de medición sincrofasorial, así como una reseña del sistema WAMS del CENACE. Posteriormente, una propuesta metodológica para determinar los límites de estabilidad estática de ángulo, es presentada. Estos límites servirán como base referencial para el monitoreo en tiempo real.

Real time monitoring of endogenous cytoplasmic mRNA using linear antisense 2'-O-methyl RNA probes in living cells.

Visualization and monitoring of endogenous mRNA in the cytoplasm of living cells promises a significant comprehension of refined post-transcriptional regulation. Fluorescently labeled linear antisense oligonucleotides can bind to natural mRNA in a sequence-specific way and, therefore, provide a powerful tool in probing endogenous mRNA. Here, we investigated the feasibility of using linear antisense probes to monitor the variable and dynamic expression of endogenous cytoplasmic mRNAs. Two linear antisense 2′-O-methyl RNA probes, which have different interactive fluorophores at the 5′-end of one probe and at the 3′-end of the other, were used to allow fluorescence resonance energy transfer (FRET) upon hybridization to the target mRNA. By characterizing the formation of the probe-mRNA hybrids in living cells, we found that the probe composition and concentration are crucial parameters in the visualization of endogenous mRNA with high specificity. Furthermore, rapid hybridization (within 1 min) of the linear antisense probe enabled us to visualize dynamic processes of endogenous c-fos mRNA, such as fast elevation of levels after gene induction and the localization of c-fos mRNA in stress granules in response to cellular stress. Thus, our approach provides a basis for real time monitoring of endogenous cytoplasmic mRNA in living cells.

New method for cooling slabs in the secondary cooling zone of continuous casters that allows computer control of the slab crystallization process

A new contact-type method is proposed for controlling the cooling of continuous-cast semifinished products in the secondary cooling zone of continuous casters. The method employs water-cooled rollers and a system that controls the flow of coolant water. The method makes it possible to directly measure the removal of heat from the product, and it is based on a series of numerical-analytical models and highly precise algorithms. It is shown that it is possible to computerize control of the quality of cast slabs on the basis of real-time monitoring of the shape of the liquid crater and regulation of the slab’s macrostructure in each section.

An Improved Gridded Historical Daily Precipitation Analysis for Brazil

Abstract A gauge-only precipitation data quality control and analysis system has been developed for monitoring precipitation at NOAA’s Climate Prediction Center (CPC). Over the past 10 yr the system has been used to develop and deliver many different precipitation products over the United States, Mexico, and Central and South America. Here the authors describe how the system has been applied to develop improved gridded daily precipitation analyses over Brazil. Consistent with previous studies, comparisons between the the gridded analyses and station observations reveal fewer dry days, a greater number of low precipitation days, and fewer extreme precipitation events in the gridded analyses. Even though the gridded analysis system reduces the number of dry days and increases the number of wet days, there is still a good correlation between time series of the gridpoint precipitation values and observations. Retrospective analyses are important for computing basic statistics such as mean daily/monthly rainfall, extremes, and probabilities of wet and dry days. The CPC gridded precipitation analyses can be used in hydrologic and climate variability studies dealing with large spatial-scale anomaly patterns, such as those related to ENSO. The analyses can also be used as a benchmark for evaluating model simulations, serve as a basis for real-time monitoring, and provide statistics on the occurrence of large-scale heavy rainfall events and dry periods.

Laboratory investigation of a multiple-model state estimation scheme for detection and isolation of leaks in pipelines

A pipeline system is an essential component in the transport of natural gases, crude and oil products in the petroleum industry, as well as gas and water in vital utility systems. Early detection of leaks in pipelines is essential to avoid excessive economical loss and reducing the environmental and health hazards that normally result from undetected leaks. In this paper, a model-based estimation scheme, which was developed as a basis for real-time monitoring of fluid flow in pipelines, is tested experimentally. In this estimation scheme, the fluid flow in a pipeline, which is modelled by a set of non-linear partial differential equations, is represented in a state-space form. A modified extended Kalman filter (MEKF), with its internal model defined by the obtained state-space form, is invoked together with feedforward computations to establish an adaptive multimodel state estimation technique. A laboratory experimental test-rig is constructed to test the validity and effectiveness of the developed leak detection and localization scheme. Experimental results utilizing the laboratory set-up are presented to demonstrate that the developed scheme effectively detects and locates leaks in pipelines within a short time duration.