A single FPGA-based portable ultrasound imaging system for point-of-care applications

We present a cost-effective portable ultrasound system based on a single field-programmable gate array (FPGA) for point-of-care applications. In the portable ultrasound system developed, all the ultrasound signal and image processing modules, including an effective 32-channel receive beamformer with pseudo-dynamic focusing, are embedded in an FPGA chip. For overall system control, a mobile processor running Linux at 667 MHz is used. The scan-converted ultrasound image data from the FPGA are directly transferred to the system controller via external direct memory access without a video processing unit. The potable ultrasound system developed can provide real-time B-mode imaging with a maximum frame rate of 30, and it has a battery life of approximately 1.5 h. These results indicate that the single FPGA-based portable ultrasound system developed is able to meet the processing requirements in medical ultrasound imaging while providing improved flexibility for adapting to emerging POC applications.     

基于DSP-FPGA平台的ADCP高沙流量测量系统

基于TMS320C6748与Spartan-6平台完成声学多普勒流速剖面仪(Acoustic Doppler Current Profiler, ADCP)的设计,并实现高含沙量情况下的水流流量精确测量。数字信号处理模块(Digital Signal Processing, DSP)完成上位机通信、系统控制、现场可编程门阵列模块(Field Programmable Gate Array, FPGA)交互、外设数据接入、信号数据处理等功能,FPGA完成发射信号调制、接收信号采集等功能。利用测量船搭载ADCP高沙流量测量系统在黄河流域进行测量,ADCP接入全球定位系统(Global Positioning System, GPS)和测深仪数据,在高含沙量水域进行断面流量测试,验证系统的可行性及测量精度。结果显示,在含沙量达到15.5 kg·m-3的水文环境下,ADCP系统可正常稳定地完成测量作业,测量得到的流量相对误差为1.01%,满足高精度流量测量系统的要求。     

A Laser System for Real-Time Measurement of the 129I and NO2 Concentrations in a Spent Nuclear Fuel Reprocessing Medium

A laser system was developed for real-time detection of the global radionuclide ¹²⁹I and NO₂ during spent nuclear fuel reprocessing. This system was used for determining the concentrations of these substances in a gas stream under actual conditions of nitric acid dissolution of spent nuclear fuel at the Khlopin Radium Institute, Research and Production Association. The tests showed that the laser system is suitable for measuring both the ¹²⁹I and NO₂ concentrations directly in the gas phase during spent nuclear fuel reprocessing (this is essential for monitoring this process and controlling the dissolution cycle safety) and in the gases emitted by radiochemical enterprises. The sensitivity with respect to ¹²⁹I, achieved with the laser system developed, also makes it suitable for real-time monitoring of ¹²⁹I and NO₂ at the maximum permissible concentration (MAC) level. This will allow evaluation of the environmental condition of air in the working areas of radiochemical enterprises, as well as in residential areas.     

Performance analysis of multipath transmission over 802.11-based multihop ad hoc networks: a cross-layer perspective

Data transmission in ad hoc networks involves interactions between medium access control (MAC)-layer protocols and data forwarding along network-layer paths. These interactions have been shown to have a significant impact on the performance of a system. This impact on multipath data transmission over multihop IEEE 802.11 MAC-based ad hoc networks is assessed; analysis is from a cross-layer perspective. Both MAC layer protocols and network-layer data forwarding are taken into account in the system models. The frame service time at source in a 802.11 MAC-based multipath data transmission system under unsaturated conditions is studied. Analytical models are developed for two packet generation schemes (round robin and batch) with a Poisson frame arrival process. Moreover, an analytical model is developed to investigate the throughput of a multipath transmission system in 802.11-based multihop wireless networks. Two methods are proposed to estimate the impact of cross-layer interactions on the frame service time in such a system. Two bounds of the system throughput are obtained based on these estimation methods. These models are validated by means of simulation under various scenarios.     

New mass transfer performance data of a cross-flow liquid desiccant dehumidification system

This paper presents new mass transfer performance data of a cross-flow liquid desiccant dehumidification system using a structured packed tower. The structured packing consists of cross-corrugated cellulose paper sheets with a surface area per unit volume ratio of 608 m² m^?3. The liquid desiccant, viz. calcium chloride, flows through the pad from top to bottom, while the air flows horizontally making it a cross-flow configuration. The experimental dehumidification effectiveness from the present study was compared with the widely used Chung's correlation (although developed for counter flow arrangement, as opposed to cross-flow in the current study) and Liu et al.'s correlation. A new empirical correlation was developed for the dehumidification effectiveness, which fitted the experimental data to within ±10%. The effect of varying air and solution inlet conditions and flow rates on the system performance was also quantified in the paper.     

Ice loads on the caisson structures in the Canadian Beaufort Sea

This paper presents a comprehensive overview of the characteristics, instrumentation and measured ice loads on the caisson structures that were used for exploratory drilling in the Canadian Beaufort Sea in the 1970s and 1980s. Details are presented on the Tarsiut Caisson, the Single-Steel Drilling Caisson (SSDC), the Caisson-Retained Island (CRI), and the Mobile Arctic Caisson (MAC) Molikpaq. The global loads on the structures are presented as a Line Load (Global Load per unit width of the structure) and the Global Pressure (Line Load per unit ice thickness). Over 170 loading events are documented. There is excellent agreement amongst the measured loads on all of the structures if factors such as ice rubble and ice thickness are considered. Global loads are shown to be a function of the ice macrostructure (level first-year sea ice, multi-year ice, first-year ridges, hummock fields, isolated floes) and failure mode of the ice (bending, creep, mixed mode, crushing). The analysis shows that there is a general increase in the Line Load with increasing ice thickness. Empirical equations are presented to predict the global load in terms of the ice thickness and structure width for different ice failure modes. The most significant result of the analysis shows that the maximum Global Pressure measured for all types of ice loading events never exceeded 2 MN/m², with the vast majority less than 1.5 MN/m².     

Studying diffusion in multilayer thin-film structures on silicon by the contact melting technique

Features of the contact melting in thin-film structures comprising an aluminum layer with a thickness of h ₁ = 5 μm and a metal (Ti, Ni, Mo) or semiconductor (Si, Ge) sublayer (h ₂ = 0.1 μm) on a single crystal silicon plate (h ₃ = 500 μm) have been studied. The contact melting was caused by single rectangular electric pulses with a current density of j < 9 × 10¹⁰ A/m² and a duration of τ = 100–1000 μs passing through the Al layer. The duration and rate of melting in the samples were determined using voltage waveforms measured by an oscillograph. A method has been developed based on an analysis of the mechanisms of contact interaction in the Al film—sublayer system (with allowance for experimental data on the time of sublayer dissolution in the Al film) for estimating the coefficients of mutiphase diffusion of the system components during the passage of a current pulse.     

Failure Analysis of a Dissolved Air Flotation Treatment Plant in a Dairy Industry

Environmental pollution in Nigeria presents an urgent need to assess wastewater treatment facilities in various industries. This article presents an assessment of dissolved air flotation (DAF) operation in a dairy industry. The industry was visited, wastewater treatment facilities were assessed (based only on efficacy to remove selected environmental health-related pollutants) and measurements of essential design and characterization parameters were taken. The study revealed that the averages of flow rate, biochemical oxygen demand at 5 days (BOD₅), chemical oxygen demand (COD), suspended solids (SS) and total solids (TS) of the influent wastewater into the plant (DAF) were 3.45 L/s, 1652.37, 3304.67, 2333.82, and 4396.10 mg/L compared to effluent quality of 560.37, 1127.33, 172.33, and 1866.67 mg/L for BOD₅, COD, SS, and TS, respectively. The pH of the wastewater is being adjusted by addition of lime before the effluent equalization tank and individual efficacies of the system were 66.09, 65.89, 65.89, 57.54, 8.68, and 94.49% for BOD₅, COD, SS, TS, DS, and total nitrogen, respectively, with overall efficacy of 38.10%. It was concluded that failure (lower overall efficacy) of the system can be attributed to setting of lime in the oversized equalization tank (50 m³ instead of 16.82 m³ per 8 h shift), the lack of application of standardized engineering code and practices (provision of underground tank in the process, lack of complete coagulation processes, coagulation and flocculation units), lack of adequate aeration unit and lack of reliable systems for automatically adjusting dosage of coagulant and flocculant. Although, DAF unit is the centerpiece of a DAF-based system design, there are several other supporting systems important to optimal DAF operation. These observations, coupled with the analysis in this report, demonstrate that the facilities necessary to minimize continuous environmental pollution are lacking. Pollution will become an increasing problem unless pollution preventing codes and standards are developed; incorporated into government regulations and the regulations are enforced.     

Effect of the level of the addition of Pb(Y0.5Nb0.5)O3 on the structure, microstructure and ferroelectric properties of PZT(53/47)

In this work an attempt is made to study [Pb(Zr_0.53Ti_0.47O₃)O₃]_1-X-[Pb(Y_0.5Nb_0.5)O₃]_X system with x = 0.0125, 0.025, 0.05, 0.075 and 0.1. It was shown that there is limited solid solubility (2.5 mol%) of Pb(Y_0.5Nb_0.5)O₃ (PYN) in PZT (53/47). The substitution of PYN gave rise to the reduction of the volume of PZT’s unit cell. For the samples doped above this level of PYN, an extra phase comprising of Y³⁺, Zr⁴⁺ and Ti⁴⁺ cations were detected based on EDS-SEM and XRD analysis and also a structural shift towards a rhombohedral phase was noticed for the main PZT phase. Further, the addition of PYN up to 2.5 mol% was seen to increase the room temperature relative permittivity and d₃₃ parameter. However, these parameters declined for the samples substituted with more than 2.5 mol% PYN due to the formation of non ferroelectric extra phase.     

汞离子频标数据采集系统的小型化设计

为实现汞离子微波频标电子伺服系统的小型化,设计了一种基于FPGA的汞离子频标数据采集系统。采用宽带、高速、低功耗的微芯片电路模块对离子跃迁谱线的微弱荧光信号进行放大、整形、降噪处理;利用FPGA高速光子计数法对信号进行采集。取代了传统的计算机软件LABVIEW与商用仪器结合的数据采集系统,实现了对离子微波频标物理系统中微弱荧光信号的有效采集。     

Highly selective ion-imprinted particles for solid-phase extraction of Pb ions

The Pb²⁺-imprinted (PHEMAC-Pb²⁺) particles were prepared by bulk polymerization as a solid-phase extraction (SPE) adsorbent. N-methacryloyl-(l)-cysteine (MAC) was used as functional monomer to have a well-shaped molecular geometry between MAC monomer and Pb²⁺ ions that provide molecular recognition based on well fitted cavities for Pb²⁺ ions after removal of template ions. The PHEMAC-Pb²⁺ particles were characterized and the applicability of these particles was investigated for the solid-phase extraction of Pb²⁺ ions from aqueous solutions and environmental samples. The PHEMAC-Pb²⁺ particles with a size range of 50–200 µm have a rough surface and macropores in bulk structure. The adsorption capacity of the PHEMAC-Pb²⁺ particles is relatively low (2.01 mg/g). However, the high selectivity towards competitive ions (Cd²⁺, Ni²⁺ and Cu²⁺) promises the PHEMAC-Pb²⁺ particles an alternative SPE adsorbent in literature. The relative selectivity coefficients of PHEMAC-Pb²⁺ particles for Pb²⁺/Ni²⁺, Pb²⁺/Cd²⁺ and Pb²⁺/Cu²⁺ were almost 71, 117 and 192 times greater than that of non-imprinted (PHEMAC) particles, respectively. Moreover, the reusability of the PHEMAC-Pb²⁺ particles was tested for several times and no significant loss in adsorption capacity was observed. The accuracy of the proposed procedure was also verified by the determination of Pb²⁺ ions in the certified reference material, LGC 6137 Estuarine sediment.     

Free-running ADC- and FPGA-based signal processing method for brain PET using GAPD arrays

Currently, for most photomultiplier tube (PMT)-based PET systems, constant fraction discriminators (CFD) and time to digital converters (TDC) have been employed to detect gamma ray signal arrival time, whereas anger logic circuits and peak detection analog-to-digital converters (ADCs) have been implemented to acquire position and energy information of detected events. As compared to PMT the Geiger-mode avalanche photodiodes (GAPDs) have a variety of advantages, such as compactness, low bias voltage requirement and MRI compatibility. Furthermore, the individual read-out method using a GAPD array coupled 1:1 with an array scintillator can provide better image uniformity than can be achieved using PMT and anger logic circuits. Recently, a brain PET using 72 GAPD arrays (4×4 array, pixel size: 3 mm×3 mm) coupled 1:1 with LYSO scintillators (4×4 array, pixel size: 3 mm×3 mm×20 mm) has been developed for simultaneous PET/MRI imaging in our laboratory. Eighteen 64:1 position decoder circuits (PDCs) were used to reduce GAPD channel number and three off-the-shelf free-running ADC and field programmable gate array (FPGA) combined data acquisition (DAQ) cards were used for data acquisition and processing. In this study, a free-running ADC- and FPGA-based signal processing method was developed for the detection of gamma ray signal arrival time, energy and position information all together for each GAPD channel. For the method developed herein, three DAQ cards continuously acquired 18 channels of pre-amplified analog gamma ray signals and 108-bit digital addresses from 18 PDCs. In the FPGA, the digitized gamma ray pulses and digital addresses were processed to generate data packages containing pulse arrival time, baseline value, energy value and GAPD channel ID. Finally, these data packages were saved to a 128 Mbyte on-board synchronous dynamic random access memory (SDRAM) and then transferred to a host computer for coincidence sorting and image reconstruction. In order to evaluate the functionality of the developed signal processing method, energy and timing resolutions for brain PET were measured via the placement of a 6 μCi ²²Na point source at the center of the PET scanner. Furthermore the PET image of the hot rod phantom (rod diameter: from 2.5 mm to 6.5 mm) with activity of 1 mCi was simulated, and then image acquisition experiment was performed using the brain PET. Measured average energy resolution for 1152 GAPD channels and system timing resolution were 19.5% (FWHM%) and 2.7 ns (FWHM), respectively. With regard to the acquisition of the hot rod phantom image, rods could be resolved down to a diameter of 2.5 mm, which was similar to simulated results. The experimental results demonstrated that the signal processing method developed herein was successfully implemented for brain PET. This reduced the complexity, cost and developing duration for PET system relative to normal PET electronics, and it will obviously be useful for the development of high-performance investigational PET systems.     

Dot chart analysis as a means to develop a fault tree: application to a catalytic hydrogenation unit

This paper describes the application of dot chart analysis to a semicontinuous catalytic hydrogenation unit. Dot chart tables have been used as a basis for developing the recursive operability analysis and the fault trees (FTs), whose aim is to determine the safety of both the unit and its operators. The unit is formed of two reactors in parallel: the transfer of operations from one reactor to the other when its catalyst is exhausted is performed by means of the isolation systems installed for this purpose on the inlet and outlet lines. FTs assessed the expected number of leak at 3×10⁻³ occurrences per mission time. The study clearly showed that the operations could be regarded as safe, since, with minor modification to control system and operative procedure, these leaks would be of pressurised nitrogen and hence without consequences for the unit and its operators.     

Water-side reversible CO2 heat pump for residential application

This paper presents the energy assessment of a water/water R744 chiller/heat pump, working according to a transcritical cycle, used for winter heating, summer cooling and tap water production. The different functions (heating, cooling, hot water) are managed water side. The analysis of the R744 chiller/heat pump is based on an original simplified method, which is able to predict the energy performance of the unit based only on its performance data at the nominal rating conditions. The method was validated against experimental data. A comparison with a state-of-the-art R410A unit is presented. The monthly analysis shows that the CO₂ unit is very efficient in hot water production, but penalised in heating and cooling service. The adoption of an ejector in place of the expansion valve makes the CO₂ system reach the same energy consumption as the R410A unit, despite the presence of the water loop only in the R744 lay-out.     

Synthesis,characterization and structural refinement of polycrystalline uranium substituted zirconolite

Ceramic precursors of Zirconolite (CaZrTi₂O₇) family have a remarkable property of substitution on Zr^{4 +} cationic sites. This makes them potential material for nuclear waste management in ‘synroc’ technology. In order to simulate the mechanism of partial substitution of zirconium by tetravalent actinides, a solid phase of composition CaZr_0.95U_0.05Ti₂O₇ has been synthesized through ceramic route by taking calculated quantities of oxides of Ca, Ti and nitrates of uranium and zirconium respectively. Solid state synthesis has been carried out by repeated pelletizing and sintering the finely powdered oxide mixture in a muffle furnace at 1050°C. The polycrystalline solid phase has been characterized by its typical powder diffraction pattern. Step analysis data has been used for ab initio calculation of structural parameters. The SEM and EDAX analysis also confirm that zirconolite acts as a host material for uranium. The powder diffraction data of 3500 points between 2θ = 10–80° has been analysed by GSAS (general structure analysis system) software to obtain the best fit of the observed data points. The uranium substituted zirconolite crystallizes in monoclinic symmetry with space group C2/c (#15). The following unit cell parameters have been calculated: a = 12.4883(15), b = 7.2448(5), c = 11.3973(10) and β = 100.615(9)°. The calculated and observed values of the intensities, lattice parameters and density measurement shows good agreement. The Rietveld analysis and GSAS based calculations for bond distance Ti—O, Ca—O, Zr—O, and O—M—O bond angles have been made. The structure was refined to satisfactory completion.The and Rp and Rwp are found to be 7.48 and 9.74 % respectively.     

Precision equipment for reproducing particle sizes and numerical concentrations in aerosols, suspensions, and powders

Precision equipment is described for reproducing the unit of numerical concentration and size for particles in aerosols, suspensions, and powders in the concentration range from 4·10⁷ to 4·10¹³ m⁻³ with average particle dimensions of 1–100 μm. The apparatus is based on small-angle laser-beam scattering and Beer's law. The optical system is described. The residual systematic error in reproducing the numerical concentration and unit does not exceed 12% in the above concentration and size ranges. Translated from Izmeritel'naya Tekhnika, No. 9, pp. 68–70, September, 1997     

Phase changes and lattice distortion in fluorite-related phases of R3TaO7 (3R2O3·Ta2O5, R=rare earth)

The crystal structuresof the compounds R₃TaO₇ (3R₂O₃·Ta₂O₅, RLaYb, Y) were studied by X-ray diffraction method. According to the powder X-ray patterns, R₃TaO₇ prepared by solid state reaction at 1700°C for for 4 h showed several polymorphic modifications based on fluorite-related structures. The diffraction patterns are of cubic fluorite-like type for smaller R³⁺ ions. For larger R³⁺ ions the superlattice lines appeared and the diffraction peak of the fundamental lines was broadened and/or apparently split, which is of weberite orthorhombic type. The orthorhombic structure has monoclinic distortion of the fluorite unit cell. With the increase of the ionic radii of R³⁺ ions until Nd³⁺, the distortion of the fluorite unit cell increased. The compounds of R₃TaO₇ with much larger radii for RLa³⁺ and Pr³⁺, however, have a different distortion type in their unit cells. Therefore, two orthorhombic fluorite related superstructures are formed, of space group Cmcm for RLa and Pr, and C222₁ for Nd, Sm, Eu, Gd, Tb and Dy. The smaller ions such as Ho, Er, Yb and Y take the cubic fluorite structure.     

Radiation shielding features for various tellurium-based alloys: a comparative study

We investigate the radiation shielding properties for four Te-based alloys. X-ray diffraction patterns revealed pure phases in all studied samples; however, a secondary phase is detected in the CrTe sample in good agreement with the literature. All samples’ densities were measured using the Archimedes principle. The mass attenuation coefficient (MAC) was calculated using Geant4 MC Toolkit and then compared with the XCOM data. Many photon-shielding properties were computed for all investigated samples based on the MAC. The Phy-X and SRIM were used to determine the fast neutron removal cross-section (Σ_R) and projected range, respectively. As a result, PbTe shows superior shielding features compared to the rest of the investigated samples to use this sample in different shielding applications.

     

Magnetic properties of the mixed spinel Co1+x Si x Fe2−2x O4

The structural and magnetic properties of the mixed spinel Co_1+x Si _x Fe_2?2x O₄ system for 0·1≤x≤0·6 have been studied by means of X-ray diffraction, magnetization, and Mössbauer spectroscopy measurements. X-ray intensity calculations indicate that Si⁴⁺ ions occupy only tetrahedral (A) sites replacing Fe³⁺ ions, and the added Co²⁺ ions substitute for (B) site Fe³⁺ ions. The Mössbauer spectra at 300 K have been fitted with two sextets in the ferrimagnetic state corresponding to Fe³⁺ at the A and B sites, forx≤0·3. The Mössbauer intensity data shows that Si possesses a preference for the A site of the spinel. The variation of the saturation magnetic moment per formula unit measured at 300 K with the Si content, is explained on the basis of Neel’s collinear spin ordering model forx≤0·3 which is supported by Mössbauer, and X-ray data. The Curie temperature decreases nearly linearly with increase of the Si content, forx=0·1–0·6.