Gas monitoring data anomaly identification based on spatio-temporal correlativity analysis

Based on spatio-temporal correlativity analysis method, the automatic identification techniques for data anomaly monitoring of coal mining working face gas are presented. The asynchronous correlative characteristics of gas migration in working face airflow direction are qualitatively analyzed. The calculation method of asynchronous correlation delay step and the prediction and inversion formulas of gas concentration changing with time and space after gas emission in the air return roadway are provided. By calculating one hundred and fifty groups of gas sensors data series from a coal mine which have the theoretical correlativity, the correlative coefficient values range of eight kinds of data anomaly is obtained. Then the gas moni- toring data anomaly identification algorithm based on spatio-temporal correlativity analysis is accordingly presented. In order to improve the efficiency of analysis, the gas sensors code rules which can express the spatial topological relations are sug- gested. The experiments indicate that methods presented in this article can effectively compensate the defects of methods based on a single gas sensor monitoring data.

GAS PATH ELECTROSTATIC SENSOR MONITORING AND COMPARISON EXPERIMENT ON TURBOJET ENGINE

A monitoring and comparison experiment with two types of sensors on a turbojet engine is carried out. Compared with a probe-typed sensor,which is designed successfully before,signals are collected to verify the validity and better feasibility of the circular sensor.According to the signals monitored over 131h,the typical signals of 125—129 phases are analyzed.The results show that the unusual exhaust particles are carbon depositions from fuel spray nozzle.Therefore,with the electrostatic sensor,early warning can be provided for initial fault condition, as well as real-time reference for the condition-based maintenance.

Study on gas monitoring technology based on information fusion

In view of the deficiency of current gas monitoring systems in coal mine roadwayexcavation, a two-level information fusion technology, which adopted the adaptiveweighted algorithm and the BP neural network technology, was applied to gas monitoring.The results show that the adaptive weighted algorithm can realize self-regulation by decreasingthe weight value of the failed sensor automatically, so as to eliminate the effect ofthe failed sensor and ensure the effectiveness and accuracy of the gas monitoring system.The BP neural network can not only effectively predict the gas gush quantity of the excavationroadway, but also accurately calculate the gas concentration in the region whereone or more sensors have failed, so as to provide the basis for judging the safety status ofthe roadway excavation.The experiments prove the superiority and feasibility of the applicationof information fusion in gas monitoring.

Optically powered gas monitoring system using single-mode fibre for underground coal mines

We present an optically powered,intrinsically safe gas monitoring system to measure four essential environmental gases(CH_(4),CO_(2),CO and O_(2)),together with ambient temperature and pressure,for underground mines.The system is based on three key technologies developed at UNSW:(1)power-over-fbre(PoF)at 1550 nm using a single industry-standard,low-cost single-mode fbre(SMF)for both power delivery and information transmission,(2)liquid–crystal-based optical transducers for optical telemetry,and(3)ultra-low power consumption design of all electronics.Together,this approach allows each gas monitoring station to operate with less than 150 mW of optical power,meeting the intrinsic safety requirements specifed by the IEC60079-28 standard.A 2-month feld trial at BMA’s Broadmeadow underground mine proved the cabling compatibility to the mine’s existing optical network and the stability of the system performance.Compared with conventional electrically powered gas sensors,this technology bypasses the usual roadblocks of underground gas monitoring where electrical power is either unsafe or unavailable.Furthermore,using one fbre for both power delivery and communication enables longer distance coverage,reduces optical cabling and increases multiplexing possibilities and data throughput for better awareness of underground environment.

Flue Gas Monitoring System With Empirically-Trained Dictionary

The monitoring of flue gas of the thermal power plants is of great significance in energy conservation and environmental protection.Spectral technique has been widely used in the gas monitoring system for predicting the concentrations of specific gas components.This paper proposes flue gas monitoring system with empirically-trained dictionary(ETD)to deal with the complexity and biases brought by the uninformative spectral data.Firstly,ETD is extracted from the raw spectral data by an alternative optimization between the sparse coding stage and the dictionary update stage to minimize the error of sparse representation.D1,D2 and D3 are three types of ETD obtained by different methods.Then,the predictive model of component concentration is constructed on the ETD.In the experiments,two real flue gas spectral datasets are collected and the proposed method combined with the partial least squares,the background propagation neural network and the support vector machines are performed.Moreover,the optimal parameters are chosen according to the 10-fold root-mean-square error of cross validation.The experimental results demonstrate that the proposed method can be used for quantitative analysis effectively and ETD can be applied to the gas monitoring systems.

Gas concentration monitoring system for small and medium-sized coal mines based on gas-sensing detection and single-chip control

This paper is aimed at the actual conditions of disaster caused by gas in small and medium-sized coal mines. A new gas concentration monitoring system for coal mines is developed on the basis of gas-sensing detection and single-chip control. The monitoring system uses the tin oxide as the main material of N-type semiconductor gas sensors, be- cause it has good sensitive characteristics for the flammable and explosive gas （ such as methane, carbon monoxide）. The QM-N5-semiconductor gas sensor is adopted to detect the output values of the resistance under the different gas con- centrations. The system, designedly, takes the AT89C51 digital chip as the core of the circuit processing hardware structure to analyze and judge the input values of the resistance, and then achieve the control and alarm for going beyond the limit of gas concentration. The gas concentration monitoring system has man）, advantages including simple in struc- ture, fast response time, stable performance and low cost. Thus, it can be widely used to monitor gas concentration and provide early wamings in small and medium-sized coal mines.

Distributed optical fiber acoustic sensor for in situ monitoring of marine natural gas hydrates production for the first time in the Shenhu Area,China

The distributed acoustic sensor(DAS)uses a single optical cable as the sensing unit,which can capture the acoustic and vibration signals along the optical cable in real-time.So it is suitable for monitoring downhole production activities in the process of oil and gas development.The authors applied the DAS system in a gas production well in the South China Sea for in situ monitoring of the whole wellbore for the first time and obtained the distributed acoustic signals along the whole wellbore.These signals can clearly distinguish the vertical section,curve section,and horizontal production section.The collected acoustic signal with the frequency of approximately 50 Hz caused by the electric submersible pump exhibit a signal-to-noise ratio higher than 27 dB.By analyzing the acoustic signals in the production section,it can be located the layers with high gas production rates.Once an accurate physical model is built in the future,the gas production profile will be obtained.In addition,the DAS system can track the trajectory of downhole tools in the wellbore to guide the operation.Through the velocity analysis of the typical signals,the type of fluids in the wellbore can be distinguished.The successful application of the system provides a promising whole wellbore acoustic monitoring tool for the production of marine gas hydrate,with a good application prospect.

Preparation and Characterization of Phosphorus Pentafluoride Gas for Lithium Ion Battery Electrolyte Salt

A novel preparation method of phosphorus pentafluoride（PF5） is introduced in details in the article. Phosphorus pentafluoride is mainly used to synthesize lithium ion battery electrolyte salt. In the experiment mesneproduct- hexafluorophosphoric acid（HPF6） was firstly prepared-from phosphorus pentoxide（P2O5） and anhydrous hydrogen fluoride（HF）, according to the chemical stoichiometrics, the optimum amount of excess HF used was about 60% and the optimum reaction time was 4 h; then HPF6 was dehydrated by oleum with an excess amount of 35%-- 40% which was heated for 40--50 min at 150 ℃; thus HPF6 was decomposed to a mixture of gases containing PF5; impurity gases were removed through condensation in the presence of cooling water at 0 ℃, then PF5 of high purity was eventually prepared. The production was characterized by inffared（IR） spectrometry and gas chromatography-mass spectroscopy-selected ion monitoring（GC-MS-SIM）. Eventual results indicate that PF5 prepared by the novel method has a high target purity and a low amount of impurity and water.

Multiple Respiratory Gas Monitoring Causes Changes of Inspired oxygen Concentration in Closed Anesthesia System

Effect of multiple respiratory gas monitoring (MRGM ) on inspiredconcentration of oxygen in circult system during closed anesthesia was studied in 5l adult patients scheduled for abdominal surgery. Required flow rate of fresh oxygen (OFR), inspired oxygen concentration (FiO2 ) and oxygen saturation of pulse oximeter (SpO2) were measured continu0usly. Patients were equally divided into three groups at randorn, group C (no MRGN used ), group M, (using MRGM with its tail gas returned to circuit system), group M2 (using MRGM without tail gas returned ). The results revealed that during 180 min of closed anesthesia, OFR required in group C and M, were about 200-230 ml/min, and in group M, it was ab0ut 400 ml/min. In group C FiO2 decreased by about 10 % after 60 min of closed anesthesia (P<0. 01, 60 min vs 0 min ) and then stayed stable at this level. In group M,, FiO2 decreased by 16% at 60 min and 34 % at 180 min and the decrease was significantly greater than that in gr0up C (P<0. 01). In group Me, FiO2 remained c0nstant during closed anesthesia, which was much high(Jr than those in group C and M,. The tail gas of Capnomac Ultima MRGM contained less oxygen than its sample gas drawn fr0m circuit system simuItaneously.

Does the advantage of transcutaneous oximetry measurements in diabetic foot ulcer apply equally to free flap reconstruction?

BACKGROUND Transcutaneous oxygen pressure(TcpO2)is a precise method for determining oxygen perfusion in wounded tissues.The device uses either electrochemical or optical sensors.AIM To evaluate the usefulness of TcpO2 measurements on free flaps(FFs)in diabetic foot ulcers(DFUs).METHODS TcpO2 was measured in 17 patients with DFUs who underwent anterolateral thigh(ALT)-FF surgery and compared with 30 patients with DFU without FF surgery.RESULTS Significant differences were observed in the ankle-brachial index;duration of diabetes;and haemoglobin,creatinine,and C-reactive protein levels between the two groups.TcpO2 values were similar between two groups except on postoperative days 30 and 60 when the values in the ALT-FF group remained<30 mmHg and did not increase>50 mmHg.CONCLUSION Even if the flap is clinically stable,sympathectomy due to adventitia stripping during anastomosis and arteriovenous shunt progression due to diabetic polyneuropathy could lead to low TcpO2 values in the ALT-FF owing to its thick fat tissues,which is supported by the slow recovery of the sympathetic tone following FF.Therefore,TcpO2 measurements in patients with DFU who underwent FF reconstruction may be less accurate than in those who did not.

Carbon dioxide accumulation during analgosedated colonoscopy: Comparison of propofol and midazolam

AIM: To characterize the profiles of alveolar hypoventilation during colonoscopies performed under sedoanalgesia with a combination of alfentanil and either midazolam or propofol. METHODS: Consecutive patients undergoing routine colonoscopy were randomly assigned to sedation with either propofol or midazolam in an open-labeled design using a titration scheme. All patients received 4 μg/kg per body weight alfentanil for analgesia and 3 L of supplemental oxygen. Oxygen saturation (SpO 2 ) was measured by pulse oximetry (POX), and capnography (PcCO 2 ) was continuously measured using a combined dedicated sensor at the ear lobe. Instances of apnea resulting in measures such as stimulation of the patient, a chin lift, a mask maneuver, or withholding of sedation were recorded. PcCO 2 values (as a parameter of sedation-induced hypoventilation) were compared between groups at the following distinct time points: baseline, maximal rise, termination of the procedure and 5 min after termination of the procedure. The number of patients in both study groups who regained baseline PcCO 2 values (± 1.5 mmHg) five minutes after the procedure was determined.RESULTS: A total of 97 patients entered this study. The data from 14 patients were subsequently excluded for clinical procedure-related reasons or for technical problems. Therefore, 83 patients (mean age 62 ± 13 years) were successfully randomized to receive propofol (n = 42) or midazolam (n = 41) for sedation. Most of the patients were classified as American Society of Anesthesiologists (ASA) Ⅱ [16 (38%) in the midazolam group and 15 (32%) in the propofol group] and ASA Ⅲ [14 (33%) and 13 (32%) in the midazolam and propofol groups, respectively]. A mean dose of 5 (4-7) mg of Ⅳ midazolam and 131 (70-260) mg of Ⅳ propofol was used during the procedure in the corresponding study arms. The mean SpO 2 at baseline (%) was 99 ± 1 for the midazolam group and 99 ± 1 for the propofol group. No cases of hypoxemia (SpO 2 < 85%) or apnea were recorded. However, an increase in PcCO 2 that indicated alveolar hypoventilation occurred in both groups after administration of the first drug and was not detected with pulse oximetry alone. The mean interval between the initiation of sedation and the time when the PcCO 2 value increased to more than 2 mmHg was 2.8 ± 1.3 min for midazolam and 2.8 ± 1.1 min for propofol. The mean maximal rise was similar for both drugs: 8.6 ± 3.7 mmHg for midazolam and 7.4 ± 3.2 mmHg for propofol. Five minutes after the end of the procedure, the mean difference from the baseline values was significantly lower for the propofol treatment compared with midazolam (0.9 ± 3.0 mmHg vs 4.3 ± 3.7 mmHg, P = 0.0000169), and significantly more patients in the propofol group had regained their baseline value ± 1.5 mmHg (32 of 41vs 12 of 42,P = 0.0004). CONCLUSION: A significantly higher number of patients sedated with propofol had normalized PcCO 2 values five minutes after sedation when compared with patients sedated with midazolam.

The Experimental WSN Network for Underground Monitoring H2 Abundance in the Mine Atmosphere Karnasurt Mine Lovozero Layered Alkaline Intrusion

We have developed specialized equipment based on hydrogen mini-MDM sensors and the WSN telecommunication technology for long-term monitoring of hydrogen content in the environment.Unlike existing methods,the developed equipment makes it possible to carry out measurements directly in the explosion zone with high discreteness in time.This equipment was tested at a large rare-earth deposit of the Lovozero alkaline pluton Karnasurt in the underground mining tunnel.We observed a short time impulse very high concentration of hydrogen in the atmosphere(more than 3 orders of normal atmosphere concentration).This discovery is very important because at the time of the explosion one can create abnormally high concentrations of explosive mixtures of hydrocarbon gases that can leaded to accidents.The high resolving power of the our measurement equipment makes it possible in the first time in practical to determine the shape of the anomaly hydrogen of such a concentration and to calculate the volumes of hydrogen released from the rocks,at first time in the practice.The shape of the anomaly usually consists of 2-3 additional peaks of the shape-“dragon-head”like.We make an first attempt is made to explain this form of anomaly in the article.The aim of the work the estimate hydrogen emission in mining ore deposit of rare earth elements.

Investigations into sensing characteristics of circular thin-plate electrostatic sensors for gas path monitoring

Circular thin-plate electrostatic sensors are promising in gas path monitoring due to their advantages of non-intrusiveness and easy installation. The spatial sensitivity and filtering effect are two important performance parameters. In this paper, an analytically mathematical model of induced charge on a circular thin-plate electrode is first derived. Then the spatial sensitivity and filtering effect of the circular electrostatic sensor are investigated by numerical calculations. Finally,experimental studies are performed to testify the theoretical results. Both theoretical and experimental results demonstrate that circular thin-plate electrostatic sensors act as a low-pass filter in the spatial frequency domain, and both the spatial filtering effect and the temporal frequency response characteristics depend strongly on the spatial position and velocity of the charged particle. These conclusions can provide guidelines for the optimal design of circular thin-plate electrostatic sensors.

Effect of hyperventilation on brain tissue oxygen pressure, carbon dioxide pressure, pH value and intracranial pressure during intracranial hypertension in pigs

To study the effect of hyperventilation on brain tissue oxygen pressure (P ti O 2) , brain tissue carbon dioxide pressure (P ti CO 2) , pH value and intracranial pressure (ICP) during intracranial hypertension in pigs. Methods: Autologous arterial blood ( 5.5 ml± 0.5 ml) was injected into the left frontal lobe by micropump to establish the model of intracerebral hematoma in pigs. After blood injection, the animals were hyperventilated for 15 minutes to decrease the pressure of carbon dioxide in arterial blood ( P aCO 2 ) to 27.35 mm*!Hg ± 11.97 mm*!Hg (1 mm*!Hg= 0.133 kPa). The mean arterial pressure (MAP), intracranial pressure (ICP), cerebral perfusion pressure (CPP), P ti O 2 , P ti CO 2 , pH value and [HCO 3 -] were continuously monitored and the blood gas was analyzed. Results: After hyperventilation, the ICP significantly decreased (P< 0.01 ), the CPP significantly increased (P< 0.05 ), while the P ti O 2 greatly decreased to the ischemic level ( 8.20 mm*!Hg± 2.50 mm*!Hg) (P< 0.01 ), the P ti CO 2 decreased (P< 0.01 ) and the pH value increased (P< 0.01 ). At the same time, blood gas analysis showed that the P aCO 2 greatly decreased and the pH value increased. Conclusions: Hyperventilation can decrease the ICP and the P ti O 2 significantly. Therefore, hyperventilation should be avoided early after brain injury. The P ti O 2 monitoring will be helpful for detecting cerebral ischemia early.

Effect of mild hypothermia on partial pressure of oxygen in brain tissue and brain temperature in patients with severe head injury

Objective: To study the changes of partial pressure of oxygen in brain tissue ( P btO 2) and brain temperature (BT) in patients in acute phase of severe head injury, and to study the effect of mild hypothermia on P btO 2 and BT. Methods: The P btO 2 and the BT of 18 patients with severe head injury were monitored, and the patients were treated with mild hypothermia within 20 hours after injury. The rectal temperature (RT) of the patients was kept on 31.5- 34.9℃ for 1-7 days ( 57.7 hours± 28.4 hours averagely), simultaneously, the indexes of P btO 2 and BT were monitored for 1-5 days (with an average of 54.8 hours± 27.0 hours). According to Glasgow Outcome Scale (GOS), the prognosis of the patients was evaluated at 6 months after injury. Results: Within 24 hours after severe head injury, the P btO 2 was significantly lower ( 9.6 mm Hg± 6.8 mm Hg, 1 mm Hg= 0.133 kPa) than the normal value (16-40 mm Hg). After treatment of mild hypothermia, the mean P btO 2 increased to 28.7 mm Hg± 8.8 mm Hg during the first 24 hours, and the P btO 2 was still maintained within the range of normal value at 3 days after injury. The BT was higher than the RT in the patients in acute phase of severe head injury, and the difference between the BT and the RT significantly increased after treatment of mild hypothermia. Hyperventilation (the partial pressure of carbon dioxide in artery (P aCO 2)≈25 mm Hg) decreased the high intracranial pressure (ICP) and significantly decreased the P btO 2. Conclusions: This study demonstrates that P ptO 2 and BT monitoring is a safe, reliable and sensitive diagnostic method to follow cerebral oxygenation. It might become an important tool in our treatment regime for patients in the acute phase of severe head injury requiring hypothermia and hyperventilation.

High Efficient Extraction of Phthalates in Aquatic Products by a Modified QuEChERS Method

A simple, environmentally friendly and high efficient extraction method was proposed for the determina- tion of five phthalates in aquatic products by gas chromatography combined with mass spectrometry detector （GC-MS）. When this method was adopted, samples were pretreated by modified QuEChERS（quick, easy, cheap, effective, rugged and safe） method. An environmentally friendly extractant（ethanol aqueous solution） replaced toxic acetonitrile for extracting phthalates in the protein-matrix samples. Fluorescence quenching spectra of bovine serum albumin（BSA） with phthalates show that there was a high-affinity interaction between phthalate and protein, de- creasing the extraction efficiency of phthalates from fish samples. However, in the 80%（volume fraction, ~） ethanol aqueous solution, a slow but full protein denaturation takes place, which would cause the unfolding of protein and the release of phthalates. Meanwhile, the fat-soluble impurities are extracted less in ^（ethanol） 80% aqueous solution than in either ~p（ethanol） 100% or hydrophobic solvents in the liquid-liquid extraction procedure. Therefore the puri- fication steps were greatly simplified. Overall recoveries were 81.77%--90.5% with limits of detection between 2.53 and 9.61 ~tg/L, and relative standard deviation values at 1.15%---4.85%. The proposed approach was satisfactorily applied to the determination of phthalates in real aquatic products, such as fish, shrimp and oyster.