Calorimetric power measurements in the EAST ECRH system

In this paper, the measurement method of calorimetric power for an electron cyclotron resonance heating（ECRH） system for EAST is presented. This method requires measurements of the water flow through the cooling circuits and the input and output water temperatures in each cooling circuit. Usually, the inlet water temperature stability is controlled to obtain more accurate results.The influence of the inlet water temperature change on the measurement results is analyzed for the first time in this paper. Also, a novel temperature calibration method is proposed. This kind of calibration method is accurate and effective, and can be easily implemented.

Investigation on the multi-hole directional coupler for power measurement of the J-TEXT ECRH system

Power measurement is necessary for an electron cyclotron resonance heating(ECRH)system.The directional coupler method has been put forward to monitor high-power microwave from gyrotrons in real time.A multi-hole directional coupler has been designed and manufactured for the 105 GHz/500 kW ECRH system on the J-TEXT tokamak.During the design process,we established the relationships between hole parameters and coupling characteristics based on the multi-hole coupling method and small-hole coupling theory.High-power tests have been carried out.The results indicated the reasonability of the theoretical design and practicality of the fabricated directional coupler.Sources of test errors have been discussed in detail,and the influences of spurious modes on the directional couplers have been emphatically analyzed.

Analysis and measurement of acoustic power in plastics ultrasonic welding process

A measuring principle for acoustic power in plastics ultrasonic welding process is introduced in this paper. Signal detection circuits of current, voltage, frequency, power for ultrasonic transducer of plastic ultrasonic welder are developed. A computer controlled measuring system is designed to sample the signals of welding process parameters. By using the designed system, the acoustic power curve during welding is calculated, saved, and displayed. And the relation between fusion state of plastics workpieces and input energy of joint is analyzed.

Placido disk-based topography versus high-resolution rotating Scheimpflug camera for corneal power measurements in keratoconic and post-LASIK eyes：reliability and agreement

AIM：To compare the repeatability/reproducibility of measurement by high-resolution Placido disk-based topography with that of a high-resolution rotating Scheimpflug camera and assess the agreement between the two instruments in measuring corneal power in eyes with keratoconus and post-laser in situ keratomileusis（LASIK）. METHODS：One eye each of 36 keratoconic patients and 20 subjects who had undergone LASIK was included in this prospective observational study. Two independent examiners worked in a random order to take three measurements of each eye with both instruments. Four parameters were measured on the anterior cornea：steep keratometry（Ks）,flat keratometry（Kf）,mean keratometry（Km）,and astigmatism（Ks-Kf）. Intra-examiner repeatability and inter-examiner reproducibility were evaluated by calculating the within-subject standard deviation（Sw）the coefficient of repeatability（R）,the coefficient of variation（Co V）,and the intraclass correlation coefficient（ICC）. Agreement between instruments was tested with the BlandAltman method by calculating the 95% limits of agreement（95% Lo A）.RESULTS：In keratoconic eyes,the intra-examiner and inter-examiner ICC were 〉0.95. As compared with measurement by high-resolution Placido disk-based topography,the intra-examiner R of the high-resolution rotating Scheimpflug camera was lower for Kf（0.32 vs 0.88）,Ks（0.61 vs 0.88）,and Km（0.32 vs 0.84）but higher for Ks-Kf（0.70 vs 0.57）. Inter-examiner R values were lower for all parameters measured using the high-resolution rotating Scheimpflug camera. The 95% Lo A were-1.28 to ＋0.55 for Kf,-1.36 to ＋0.99 for Ks,-1.08 to ＋0.50 for Km,and-1.11 to ＋1.48 for Ks-Kf. In the post-LASIK eyes,the intra-examiner andinter-examiner ICC were 〉0.87 for all parameters. The intra-examiner and inter-examiner R were lower for all parameters measured using the high-resolution rotating Scheimpflug camera. The intra-examiner R was 0.17 vs 0.88 for Kf,0.21 vs 0.88 for Ks,0.17 vs 0.86 for Km,and 0.28 vs 0.33 for Ks-Kf. The inter-examiner R was 0.09 vs 0.64 for Kf,0.15 vs 0.56 for Ks,0.09 vs 0.59 for Km,and 0.18 vs 0.23 for Ks-Kf. The 95% Lo A were-0.54 to ＋0.58 for Kf,-0.51 to ＋0.53 for Ks and Km,and-0.28 to ＋0.27 for Ks-Kf. CONCLUSION：As compared with Placido disk-based topography,the high-resolution rotating Scheimpflug camera provides more repeatable and reproducible measurements of Ks,Kf and Ks in keratoconic and post-LASIK eyes. Agreement between instruments is fair in keratoconus and very good in post-LASIK eyes.

The Wavefront Power Spectral Density Measurement of Aspheric Lens with Long Focal-Length Using a Computer-Generated Hologram

To ensure the performance of the optical system, the machining accuracy of lens with long focal lengths is required to ensure the image quality. A new method for lens transmission wavefront power spectral density (PSD) in mid-frequency domain measurement using binary phase computer-generated hologram (CGH) is presented. This technique is widely applicable and is particularly useful for measuring large-size lenses with long focal lengths. A comparison experiment of the CGH measurement with results from a Fizeau sphere interferometry method is carried out to verify the accuracy and convenience of the measurement. Furthermore, measurement uncertainty due to CGH fabrication process is analysed. Analysis of the CGH test showed the overall accuracy of less than 1 nm RMS for a sphere lens with over 30 m focal length and Φ410 mm clear aperture. CGH can provide reference spheres with high precision, in the meantime greatly shorten air space, thus reducing the effect of vibration and air turbulence, therefore is of great importance for lens transmission wavefront PSD measurement. The realization of high precision, high efficiency and nondestructive testing of long focal-lens wavefront PSD ensure the ultra-precision and certainty level of machining, hence improving the comprehensive performance of the optical system.

Study of a 105 GHz short-pulse dummy load for the electron cyclotron resonance heating system with the quasi-optical method

The accurate power measurement is important for an ECRH system in tokamak.The dummy load is designed and developed for the measurement of the millimeter wave power.This work analyzes the dummy load based on the quasi-optical method and the ray tracing method.The reflectivity and thermal deposition of the dummy load have been considered to ensure the safety of the entire system.High-power tests have been carried out at a 105 GHz/500 kW ECRH system.The results of the tests indicate that the designed dummy load is stable and valid.

Development of a Module for Measuring Electrical Variables in Power Transformers Based in IoT,to Manage and Monitoring by Telemetry Mechanism

This work shows the development of a module that performs measurements of electrical variables in a low voltage power transformer.These variables are sent by means of the IEEE802.11 standard,connecting to a database stored in the cloud;associating with the meter IoT concepts,this to allow a client to perform an analysis,monitoring and management of their electrical network.For the construction of this module,non-invasive current sensors connected to a three-phase meter are used and a communication card is used that allows data to be extracted from the meter and sent to the cloud database.This module,to convert a conventional electrical power transformer into a smart electrical power transformer,making it a Smart Object and thus extract information from it telemetrically in real time.

Adventures Beyond Amdahl's Law:How Power-Performance Measurement and Modeling at Scale Drive Server and Supercomputer Design

Amdahl’s Law painted a bleak picture for large-scale computing.The implication was that parallelism was limited and therefore so was potential speedup.While Amdahl’s contribution was seminal and important,it drove others vested in parallel processing to define more clearly why large-scale systems are critical to our future and how they fundamentally provide opportunities for speedup beyond Amdahl’s predictions.In the early 2000s,much like Amdahl,we predicted dire consequences for large-scale systems due to power limits.While our early work was often dismissed,the implications were clear to some:power would ultimately limit performance.In this retrospective,we discuss how power-performance measurement and modeling at scale led to contributions that have driven server and supercomputer design for more than a decade.While the influence of these techniques is now indisputable,we discuss their connections,limits and additional research directions necessary to continue the performance gains our industry is accustomed to.

Measurement of acoustic field radiated by low frequency power ultrasonic transducer with laser-interferometer

Based on the piezo-optic effect of medium, the refractive index of medium is the function of its density, and so it's also the function of acoustic pressure. Therefore, acoustic pressure in the optical path everywhere can be determined absolutely by laser-interferometric technique and relative distribution of pressure in the middle and far acoustic field, which can be obtained from theory or experiment respectively. Theory and experiment of measurement of pressure in acoustic field with laser-interferometer are introduced. Distribution of pressure radiated by a power ultrasonic transducer is determined by laser interferometric technique. The theoretical and experimental results are in good agreement. The receiving sensitivity of a PVDF (Polyvinylidene fluoride) transducer in free field is also calibrated absolutely due to above results and its sensitivity is -118.5 dB.

Radiation force on absorbing targets and power measurements of a high intensity focused ultrasound (HIFU) source

Based on the analytic expressions for the radiated field of a circular concave piston given by Hasegawa et al.,an integral for calculation of the radiation force on a plane absorbing target in a spherically focused field is derived.A general relation between acoustic power P and normal radiation force Fn is obtained under the condition of kr 1.Numerical computation is carried out by using the symbolic computation program for practically focused sources and absorbing circular targets.The results show that,for a given source,there is a range of target positions where the radiation force is independent of the target's position under the assumption that the contribution of the acoustic field behind the target to the radiation force can be neglected.The experiments are carried out and confirm that there is a range of target positions where the measured radiation force is basically independent of the target's position even at high acoustic power (up to 700 W).It is believed that when the radiation force method is used to measure the acoustic power radiated from a focused source,the size of the target must be selected in such a way that no observable sound can be found in the region behind the target.

Application of piezoelectric transient response in transducer acoustic power measurement

To explore a more convenient method for measuring the focused ultrasound power, a piezoelectric ceramic plate was used to receive ultrasonic signal directly. Due to an acoustic force acts on the surface of piezoelectric ceramic plate, the piezoelectric response was obtained by means of electromechanical analogy, which was composed of voltage response caused by forced vibration and high frequency attenuation response caused by natural vibration. The conversion relationship between output signal of piezoelectric ceramic plate and acoustic power of transducer was analyzed. The envelope of output piezoelectric signal was extracted in twice, and a voltage amplitude curve with sinusoidal distribution that could describe the changes of acoustic power was obtained. Under different drive voltage of transducer, the maximum peak voltage of envelope curve was found respectively. Their squared values were made a linear fitting with acoustic power measured by acoustic power meter, and then the proportional coefficient of theoretical relational expression was calibrated. The experimental results are in good agreement with the theory. The relative error between calibrated theoretical acoustic power and that measured by acoustic power meter was less than 8.7%. The paper can provide a guideline for measuring acoustic power of transducer by using piezoelectric signal.

BERNOULLI CONVOLUTIONS ASSOCIATED WITH CERTAIN NON-PISOT NUMBERS

The Bernoulli convolution ν λ measure is shown to be absolutely continuous with L 2 density for almost all 12<λ<1,and singular if λ -1 is a Pisot number. It is an open question whether the Pisot type Bernoulli convolutions are the only singular ones. In this paper,we construct a family of non-Pisot type Bernoulli convolutions ν λ such that their density functions,if they exist,are not L 2. We also construct other Bernolulli convolutions whose density functions,if they exist,behave rather badly.

Smart inverter operation in distribution networks with high penetration of photovoltaic systems

With the growing number and capacity of photovoltaic(PV)installations connected to distribution networks,power quality issues related to voltage regulation are becoming relevant problems for power distribution companies and for PV owners.In many countries,like Italy,this has required the revision of the standards concerning the connection to the public distribution network of distributed renewable generation.The new standards require a flexible operation of generation plants that have to be capable to change the active and reactive power dynamically in function of the network parameters(i.e.frequency and network local voltage)in local control or following external commands.Therefore,this paper investigates the use of smart inverter in a critical PV installation,where relevant voltage fluctuations exist.A case study,with real network parameters monitoring data and measurements,is discussed in the paper with the aim of showing how‘smart’features of new inverters can be implemented to increase PV plant integration in low voltage distribution networks.

Effect of the PTO damping force on the wave pressures on a 2-D wave energy converter

The information of the wave loads on a wave energy device in operational waves is required for designing an efficient wave energy system with high survivability. It is also required as a reference for numerical modeling. In this paper, a novel system, which integrates an oscillating wave energy converter with a pile-restrained floating breakwater, is experimentally investigated in a 2-D wave flume. The measurements of the wave pressure on the wet-surface of the device are made as the function of the power take-off（PTO） damping force. It is shown that the wave pressure is significantly affected by the PTO system, in particular, at the edges, and the wave pressure varies under different wave conditions. From the results, conclusions can be drawn on how the PTO damping force and wave conditions affect the loads on the device, which is of engineering concern for constructing safe and reliable devices.

Nonlinear characterization of GaN HEMT

DC I-V output,small signal and an extensive large signal characterization（load-pull measurements） of a GaN HEMT on a SiC substrate with different gate widths of 100μm and 1 mm have been carried out.From the small signal data,it has been found that the cutoff frequencies increase with gate width varying from 100μm to 1 mm,owing to the reduced contribution of the parasitic effect.The devices investigated with different gate widths are enough to work in the C band and X band.The large signal measurements include the load-pull measurements and power sweep measurements at the C band（5.5 GHz） and X band（8 GHz）.When biasing the gate voltage in class AB and selecting the source impedance,the optimum load impedances seen from the device for output power and PAE were localized in the load-pull map.The results of a power sweep at an 8 GHz biased various drain voltage demonstrate that a GaN HEMT on a SiC substrate has good thermal conductivity and a high breakdown voltage,and the CW power density of 10.16 W/mm was obtained.From the results of the power sweep measurement at 5.5 GHz with different gate widths, the actual scaling rules and heat effect on the large periphery device were analyzed,although the effects are not serious. The measurement results and analyses prove that a GaN HEMT on a SiC substrate is an ideal candidate for high-power amplifier design.