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A novel ice monitoring system for the overhead transmission lines based on fiber Bragg grating (FBG) sensing is proposed in this paper. Compared to the existing systems, this system has several unique advantages, such as unnecessary power supply onsite, excellent ability for avoiding electromagnetic interference, and long lifespan. First, two near-elliptical-shaped concavities with FBG in each side are designed on the column structure to improve accuracy in measuring eccentric load. Then, a high reliability and high resolution tilt sensing section is developed based on a beam of uniform strength where an FBG is fixed on. Finally, an unforced FBG is placed in the sensor to solve the cross-sensitivity of strain and temperature in FBG sensing. Tension and angle experiments are conducted in our laboratory to calibrate the sensor. The tension experiment results indicate that the sensor is sensitive to tension, and the sensitivity and resolution of the sensor are 0.0413 pm/N and 24.21 N. The results of the tilt angle experiment show that the sensitivity and resolution of the sensor is 16.17 pm/° and 0.0619°. The temperature effect on the tension and angle measurement, evaluated by putting the sensor in an oven, is less than ±0.3% and ±0.38% separately. A 250-h outdoor experiment was carried out in the testing field, and the results prove the sensor can work properly in harsh environments and no creep is observed during the experiment.

Disconnector switching operations in large gas-insulated switchgear (GIS) systems may produce very fast transient overvoltages (VFTOs), causing high electric stress to other apparatuses in the substation, such as power transformers. This paper presents a VFTO measuring technique based on a transformer bushing sensor, which consists of the transformer bushing (C1) and a capacitor sensor (C2) installed at the test tap of transformer bushing. In order to solve the problem of the frequency limitation of the transformer bushing sensor for measuring VFTO, a convolution model on the square-wave response of the transformer bushing sensor is introduced to obtain the frequency response of the transformer bushing sensor, and a deconvolution model based on the incremental Wiener filter is applied to reconstruct the input transient voltage waveform at the tip of the bushing by using the output signals from the bushing sensor. A 110-kV transformer bushing sensor and a fast transient overvoltage source are built in our laboratory. The results from the laboratory indicate that a transient voltage can be measured correctly based on our technique with the 110-kV transformer bushing sensor. A 750-kV transformer bushing sensor is built in a 750-kV substation. The measuring results from the 750-kV substation by using our technique show that the peak value of the VFTO produced by the disconnector (AIS) switching off operations is about 775 kV, and the dominant oscillating frequencies of the VFTO are 3.5 MHz, 1.6 MHz, and 650 kHz.

Background With the significant improvement in the survival of patients with nasopharyngeal carcinoma (NPC) undergoing radiotherapy and the growing availability of the sophisticated imaging modalities, the number of radiation encephalopathy (RE) cases relating to NPC radiotherapy is increasing. In this study, we investigated the metabolic and density changes of the compromised brain tissues during delayed RE using a positron-emission tomography-computed tomography (PET/CT) to provide clinical evidences for the diagnosis of delayed RE following radiotherapy for NPC. Methods The PET/CT manifestations and the clinical data of 53 pathologically confirmed NPC patients with delayed RE following radical radiotherapy and 15 healthy volunteers were investigated. The standardized uptake values (SUV) of the bilateral temporal lobes, the occipital lobe and the brain stem were measured respectively; and then the metabolic reduction rate of 88 temporal lobes and 13 brain stems were calculated for a statistical comparison between the two groups. Results The earliest case of delayed RE in the investigated patients occurred 1.5 years after radiotherapy. Delayed RE frequently involved the inferior temporal lobe. For patients with delayed RE confirmed by clinical symptoms and imaging findings, PET maintained a 100% coincidence rate with CT; however, in the 25 temporal lobes of the 35 delayed RE patients, PET revealed obvious hypometabolic changes whereas CT displayed normal density. The incidence of brain stem metabolic reductions was 24.5% (13/53) in the investigated patients, including 4 patients with hypometabolic changes shown by PET and negative finding shown by CT. The incidence of granuloma adjacent to the hypometabolic region in the temporal lobe was 12.5% (11/88). Conclusion Delayed RE patients exhibit significant hypometabolic changes in the inferior temporal lobe, captured by PET much earlier than by CT. PET/CT offers a valuable means for the diagnosis of delayed RE in subacute stages and granuloma formation.

In order to improve numerical performance of grounding computation of horizontal multilayer earths, a new type of complex image method has been presented. A closed form expression of Green's function with arbitrary soil parameters, source/observation position has been derived. The infinite value of coefficients A/B in Green's function has been obtained by derived closed form expression. Though numerical value of A/B can be obtained by symbolic algorithms, GNU multiple precision algorithms provides a more simple and reliable way to solve the linear equations of A/B. Then, multi-resolution complex image (MRCIM) method was presented for improvement on both stability and accuracy in numerical grounding computation of horizontal multilayer soils. MRCIM consists of adaptive sampling, decomposition of sampling space, and automations of complex image method approximation. The formula of numerical error by MRCIM has been derived. The validity of MRCIM has been proved by comparative cases. Numerical results show that, during the earth surface potential (ESP) calculation for HVDC transmission earth-return current, DC grounding electrodes can be treated as a current point when observation point is away from over 10 times of dimension of electrodes.

A 41-year-old male patient was admitted to the General Hospital of Guangzhou Military Command due to upper abdominal pain persisting for 12 h. Computed tomography (CT) and positron emission tomography/CT scans revealed multiple soft-tissue shadows in the abdominal cavity, peritoneum and Glisson's capsule, but the metabolic activity was at normal levels. A small area of low-density shadows near the tail of the pancreas and multiple shadows of enlarged lymph nodes were identified around the porta hepatis and the pancreas, with a mildly increased metabolic activity. On the basis of the CT images the patient was diagnosed with pancreatitis. Radionuclide imaging showed the absence of the spleen from its normal position (following splenectomy), but abnormal phagocytosis of multiple red blood cells was observed in the abdomen, which was diagnosed as ectopic splenic autotransplantation (ESAT). The patient subsequently recovered well following symptomatic treatment. ESAT in trauma patients requires urgent surgery in order to remove the damaged spleen and artificially cultivate partial splenic tissue.

Ground conductor is easily broken when ice accumulates on it. Thus a novel Fiber Bragg Grating (FBG) sensor is proposed to measure the tension of the ground conductor to warning the danger. The factors affecting the sensitivity of the sensor are studied. The results of tension experiment indicate the sensitivity and resolution of the sensor are 0.2286pm/N and 2.18N respectively, and both of them can be easily altered by the equation proposed. The temperature effect on the measurement, which is caused by the crosstalk of FBG, is reduced by setting a zero-force FBG. The error of the sensor caused by temperature, evaluated by putting the sensor in an oven, is lower than 10 pm from −30 °C to 50 °C. An ice simulation platform is build in our laboratory, the results show the relative error of the simulated ice load calculated by the output of the sensor is lower than 5%.

Icing of high voltage transmission lines poses a great threat to the safety of the power grid. A Fiber Bragg Grating (FBG) load sensor is developed to monitor the load of the conductor. The major factor affecting the accuracy of the sensor is the structure of elastic element, and a novel closed-loop U structure is proposed to improve the accuracy. Finite Element Method (FEM) is introduced to investigate the strain distribution on the traditional structure and novel structure under axial load and eccentric load. The results of load experiment carried out in our laboratory indicate the sensor sensitivity is 0.0407pm/N and the sensor resolution is 24.57N.

Ice monitoring on the overhead transmission lines is very important to insure the power grid safe during the ice disaster. To solve the electromagnetic interference, a tension sensor based on Fiber Bragg Grating is developed to measure the tension of the power transmission line. The sensitivity of the sensor is 0.2286 pm/N calibrated with a test machine. The relative error of the load and sag, measured by the FBG sensing system, are smaller than 5% and 2% respectively based on our ice simulation system.

Disconnector operations in GIS may generate very fast transient overvoltage (VFTO), which is characterized by its high peak value, short rise time, and high frequencies. Mostly, researches on VFTO are focusing on the apparatus involving in the active circuit. However, VFTO may pass through open devices by electromagnetic coupling. To measure VFTO under this situation, lots of field experiments have been carried out in a 750 kV substation. VFTO is measured at the test tap of the high voltage reactor bushing, using the sensor we developed. In one of the experiments, the breaker is kept open, VFTO is generated by disconnector operations (in AIS) on one side of the breaker and measured on the other side. Results show that under this situation, VFTO could reach the peak values of about 55 kV and - 70 kV, the main oscillation frequencies are about 236 kHz, 535 kHz and 1.59 MHz. To verify this case further, computer simulation has also been carried out in the laboratory with the help of ATP. The results agree with each other well.

A capacitive sensor has been developed for the measurements of very fast transient over-voltages (VFTO) in GIS. Step response measurement was performed on the sensor. It is shown from the test that the settling time is less than 20 ns and the response time is less than 2ns, suitable to the IEC1321-1. The sensor has been calibrated by power frequency voltage, impulse voltage, the division ratio of the power frequency voltage is almost as the same as that of the impulse voltage, the maximum error was less than 1.3%. The sensor was mounted in a 126KV GIS test setup to measure the transients produced by the air gap discharges. The measurement results demonstrated that the sensor is able to measure the transients with 10ns rise-time successfully.

Disconnector switching operations in large gas insulated switchgear (GIS) systems may cause very fast transients overvoltages (VFTO), which produce dielectric stress to transformer connecting with the disconnector. A VFTO bushing sensor is developed to measure the VFTO at the transformer entrance. Since the high frequency ratio of the bushing sensor is not constant, calibration before the field measurement is needed. Based on the convolution model and step response, a new calibration method is used to identify the frequency response of the bushing sensor. Calibration of an 110 kV rated bushing sensor is carried on in our laboratory to investigate the effectiveness of this method, and the calibrated results agree well with the amplitude-response gained by frequency sweep test, which demonstrates the calibrating method can be applied in VFTO bushing sensor calibration. Calibration of an UHV rated bushing sensor is processed in a factory and the frequency response of the sensor is given at the end of the paper.

To study the effects of lead acetate on the expression of brain-derived neurotropic factor (BDNF) and its receptor P75NTR in rat brain.Lead acetate was given to SD rats by intraperitoneal injection (ip) for 5 days at the dosage of 25, 50 and 100mg/kg body weight respectively. The contents of lead in serum, cerebral cortex and hippocampus were measured by atomic absorption spectrophotochemistry. The levels of BDNF mRNA and protein expression in cerebral cortex and hippocampus were observed by RT-PCR and immunohistochemistry, respectively. The levels of P75NTR protein expression in rat brain were measured by immunohistochemistry.Compared with the control, the contents of lead were significantly increased in serum, cerebral cortex and hippocampus in the treatment groups respectively (P0.01, P0.05). The BDNF mRNA expression in the cerebral cortex (0.52 +/- 0.05, 0.33 +/- 0.03) and hippocampus (0.77 +/- 0.10, 0.92 +/- 0.08) of 50, 100 mg/kg treated groups was significantly higher than that of the control group (0.52 +/- 0.05, 0.33 +/- 0.03), respectively (P0.05). The results of immunohistochemistry showed that the area density of BDNF protein in cerebral cortex of every treatment group (0.040 +/- 0.027, 0.048 +/- 0.027, 0.086 +/- 0.040) was significantly increased whereas the average gray value (187.11 +/- 11.15, 180.53 +/- 5.82, 180.15 +/- 8.01) was significantly lower than that of the control (0.026 +/- 0.005, 204.98 +/- 3.45) (P0.05, P0.01). The area density of BDNF protein in hippocampus of every treatment group was 0.040 +/- 0.027, 0.048 +/- 0.027, 0.086 +/- 0.040, respectively, which was significantly increased compared with the control (0.045 +/- 0.019, P0.05). The average gray value of BDNF protein in hippocampus (181.03 +/- 5.16, 171.25 +/- 12.65) of 50, 100 mg/kg were significantly lower than that of the control (198.98 +/- 6.40, P0.01). There was no positive expression of P75NTR protein in the control and 25 mg/kg body weight groups. The positive expression of P75NTR protein was detected in 50 and 100 mg/kg body weight groups.Lead can increase the BDNF and P75NTR expression in rat brain which might play an important role in the neural damage and repair.