Initial Set Value Research Articles

Characterization of Single Event Effect in a Radiation Hardened Programmable Read-Only Memory in a 130 nm Bulk CMOS Technology

The concept of memory that can only be read but cannot be changed seems strange at first. In reality, it is found that it has great application potential, such as the processor with a fixed purpose, the initial set value of the microprocessor BIOS, and these data are stored in Programmable Read-Only Memory (PROM) to quickly realize system functions. The PROM storage content is fixed, greatly simplifying his design. The radiation of space particles is the main factor causing the failure of the electronic system of spacecraft. The PROM storage array of the space electronic system is the most basic guarantee for the normal operation of the electronic system. The chip adopts domestic 130 nm standard technology of Complementary Metal Oxide Semiconductor (CMOS), Muller-C digital filter is used in the peripheral subsystem of PROM storage array, and the core cell uses Dual Interlocked Cell (DICE) and ring gate and other radiation hardening technologies to design a 32Kx8bit radiation resistant asynchronous programmable PROM. Pre-silicon of devices was verified by Technology Computer Aided Design (TCAD), and post silicon radiation verification was completed through radiation experiment. The post silicon radiation experiment showed that the total ionizing Dose (TID) capacity of the PROM chip was ≥100 Krad (Si), the critical value of single event upset (SEU) was ≥37.1 MeV·cm2/mg, the critical value of single event latch up was ≥98 MeV·cm2/mg, meeting the life requirements of the initial value storage of aerospace electronic systems. These performances ensure the reliable operation of the space electronic system after restart.

Clinical application of regional citrate anticoagulation for continuous renal replacement therapy in children with liver injury.

BackgroundRegional citrate anticoagulation (RCA) is increasingly used for continuous renal replacement therapy (CRRT) in children, but it is rarely used in children with liver injury, especially liver failure (LF). We analyze this issue through the following research.MethodsWe retrospectively analyzed 75 children with liver injury who underwent RCA-CRRT in the Pediatric Intensive Care Unit (PICU) of Children's Hospital of Chongqing Medical University. The patients were divided into the LF group and liver dysfunction (LD) group. The two groups were compared to evaluate the clinical safety and efficacy of RCA-CRRT in children with liver injury and to explore RCA-CRRT management strategies, in terms of the following indicators: the incidence of bleeding, clotting, citrate accumulation (CA), acid–base imbalance, and electrolyte disturbance, as well as filter lifespans, changes in biochemical indicators, and CRRT parameters adjustment.ResultsThe total incidence of CA (TCA) and persistent CA (PCA) in the LF group were significantly higher than those in the LD group (38.6 vs. 16.2%, p < 0.001; 8.4 vs. 1.5%, p < 0.001); and the CA incidence was significantly reduced after adjustment both in the LF (38.6 vs. 8.4%, p < 0.001) and LD groups (16.2 vs. 1.5%, p < 0.001). The incidence of hypocalcemia was significantly higher in the LF group than in the LD group either before (34.9 vs. 8.8%, p < 0.001) or after treatment (12.0 vs. 0%, p < 0.001). The speed of the blood and citrate pumps after adjustment was lower than the initial setting values in both the LF and LD groups. The dialysis speed plus replacement speed were higher than the initial settings parameters.ConclusionFor children undergoing RCA-CRRT, the risks of CA and hypocalcemia are significantly higher in children with liver failure than those with liver dysfunction, but through the proper adjustment of the protocol, RCA-CRRT can still be safely and effectively approached for children with LD and even LF.

A clinical study on the wean effect of setting parameters of proportional pressure support on acute exacerbation of chronic obstructive pulmonary disease patients with difficult weaning

To investigate the clinical effect of setting proportional pressure support (PPS) parameters by target tidal volume (VT) method. The study was conducted retrospectively on acute exacerbation of chronic obstructive pulmonary disease (AECOPD) patients admitted to Tianjin Third Central Hospital from January 2016 to December 2020. According to the PPS parameter setting method, the patients were divided into the airway blocking group and target VT group. The baseline characteristics, initial setting values of flow assist (FA) and volume assist (VA), respiratory system parameters, and clinical outcomes were collected and compared between the two groups. Fifty-nine patients were enrolled, 29 patients in the airway blocking group, and 30 in the target VT group. There was no statistically significant difference in baseline characteristics, compliance, resistance, and initial settings of FA and VA between the two groups. Compared with the target VT group, the respiratory rate (RR), mean arterial pressure (MAP), VT, and arterial partial pressure of oxygen (PaO2) recorded 1 hour after the initial setting of the PPS parameters in the airway block method group were significantly reduced [RR (times/minute): 21.0 (18.5, 22.5) vs. 23.0 (21.0, 25.0), MAP (mmHg, 1 mmHg = 0.133 kPa): 84.0 (79.0, 90.5) vs. 90.0 (87.0, 96.2), VT (mL): 305.24±41.07 vs. 330.87±46.84, PaO2 (mmHg): 68.0 (66.0, 73.5) vs. 74.0 (69.8, 82.5), all P < 0.05], while arterial partial pressure of carbon dioxide (PaCO2) and oral closure pressure (P0.1) were both increased significantly [PaCO2 (mmHg): 41.0 (39.0, 46.0) vs. 37.5 (35.0, 42.2), P0.1 (cmH2O, 1 cmH2O = 0.098 kPa): 1.42±0.78 vs. 0.90±0.67, both P < 0.05]. Compared with airway blocking group, the duration of weaning, ICU stay, and hospital stay in the target VT group were significantly shorter [duration of weaning (hours): 42.0 (24.0, 70.5) vs. 64.0 (30.5, 97.5), ICU stay: 10.00±3.38 to 13.28±5.41, hospital stay (days): 12.07±3.40 vs. 15.41±5.60, all P < 0.05]. There was no statistically significant difference in the invasive mechanical ventilation time, weaning failure rate, ICU mortality and in-hospital mortality between the two groups. This study suggested that the target TV method has the advantages of practicality, safety, convenience, and rapid to set PPS parameters than the airway block method, which shortens the duration of weaning and ICU stay, and has a good clinical prospect.

Abatement of the Increases in Cooling Energy Use during a Period of Intense Heat by a Network-Based Adaptive Controller

Various methods to control thermal conditions of building spaces have been developed to investigate their performances of energy use and thermal comfort in the system levels. However, the high control precision used in several studies dealing with data-driven methods may cause energy increases and the high energy efficiency may be disadvantageous for maintaining indoor environmental quality. This study proposes a model that optimizes the supply air condition to effectively reach the setting values by two-way controls of the supply air conditions. In such a process, if the results of the thermal comfort level are outside the range of the initial setting values, an adaptive model starts to work to send additional signals to adjust the set-point temperature. In order to assess its efficiency, the conventional thermostat model and fuzzy deterministic model are adopted as comparators. Comparing the results of the proposed network-based model with conventional control models, an improved control performance from 15.5% to 29.3% in thermal comfort indices was identified, as well as an over 30% improvement in energy efficiency. As a consequence, the network-based adaptive control rule supervising thermal comfort indices properly operates to abate increases in its energy use without compromising its thermal comfort. This performance can be significant in places where many spaces are woven at high density, and in situations where better thermal comfort can increase users’ workability and productivity.

Effect of Permissive Mild Hypercapnia on Cerebral Vasoreactivity in Infants: A Randomized Controlled Crossover Trial.

Mechanical ventilation interferes with cerebral perfusion via changes in intrathoracic pressure and/or as a consequence of alterations in CO2. Cerebral vascular vasoreactivity is dependent on CO2, and hypocapnia can potentially lead to vasoconstriction and subsequent decrease in cerebral blood flow. Thus, we aimed at characterizing whether protective ventilation with mild permissive hypercapnia improves cerebral perfusion in infants. Following ethical approval and parental consent, 19 infants were included in this crossover study and randomly assigned to 2 groups for which the initial ventilation parameters were set to achieve an end-tidal carbon dioxide (Etco2) of 6.5 kPa (group H: mild hypercapnia, n = 8) or 5.5 kPa (group N: normocapnia, n = 11). The threshold was then reversed before going back to the initial set value of normo- or hypercapnia. At each step, hemodynamic, respiratory, and near-infrared spectroscopy (NIRS)-derived parameters, including tissue oxygenation index (TOI) and tissue hemoglobin index (THI), concentration of deoxygenated hemoglobin (HHb) and oxygenated hemoglobin (O2Hb), were collected. Concomitantly, sevoflurane maintenance concentration, ventilatory (driving pressure) and hemodynamic parameters, as mean arterial pressure (MAP), were recorded. Targeting an Etco2 of 5.5 kPa resulted in significantly higher mean driving pressure than an Etco2 of 6.5 kPa (P < .01) with no difference between the groups in end-tidal sevoflurane, MAP, and heart rate. A large scatter was observed in NIRS-derived parameters, with no evidence for difference in Etco2 changes between or within groups. A mild decrease with time was observed in THI and MAP in infants randomly assigned to group N (P < .036 and P < .017, respectively). When pooling all groups together, a significant correlation was found between the changes in MAP and TOI (r = 0.481, P < .001). Allowing permissive mild hypercapnia during mechanical ventilation of infants led to lower driving pressure and comparable hemodynamic, respiratory, and cerebral oxygenation parameters than during normocapnia. Whereas a large scatter in NIRS-derived parameters was observed at all levels of Etco2, the correlation between TOI and MAP suggests that arterial pressure is an important component of cerebral oxygenation at mild hypercapnia.

Crowd management COVID-19

Crowds are a source of transmission in the COVID-19 spread. Contention and mitigation measures have focused on reducing people’s mass gathering. Such efforts have led to a drop in the economy. The application of a vaccine at a world level represents a grand challenge for humanity, and it is not likely to accomplish even within months. In the meantime, we still need tools to allow the people integration into their regular routines reducing the risk of infection. In this context, this paper presents a solution for crowd management. The aim is to monitor and manage crowd levels in interior places or point-of-interests (POI), particularly shopping centers or stores. The solution is based on a POI recommendation system that suggests the nearest safe options upon request of a particular POI to visit by the user. In this sense, it recommends places near the user location with the least estimated crowd. The recommendation algorithm uses a top-K approach and behavioral game theory to predict the user’s choice and estimate the crowd level for the requested POI. To evaluate the efficiency of this technological intervention in terms of the potential number of contacts of possible COVID-19 infections and the recommendation quality, we have developed an agent-based model (ABM). The adoption level of new technologies can be related to the end-user experience and trust in such technologies. As the end-user follows a recommendation that leads to uncrowded places, both the end-user experience and trust increased. We study and model this process using the OCEAN model of personality. The results from the studied scenarios showed that the proposed solution is widely adopted by the agents, as the trust factor increased from 0.5 (initial set value) to 0.76. In terms of crowd level, these are effectively managed and reduced on average by 40%. The mobility contacts were reduced by 40%, decreasing the risk of COVID-19 infection. An APP has been designed to support the described crowd management and contact tracing functionality. This APP is available on GitHub.

Exploration of the effects of pressure on the controllability of extractive distillation for separating pressure-sensitive azeotropes

Exploring the influence of steady-state process parameters on dynamic control structures is receiving increasing attention from researchers. In this work, the effects of pressure on dynamic control structures and anti-disturbance were discussed based on the minimal total annual cost. Ethanol-benzene and ethanol-ethyl acetate, two binary azeotropic systems, were used to investigate the influence of pressure on the dynamic controllability. For ethanol-benzene, the control structures with two solvents, 1,2-propanediol and p-xylene, under the optimal pressure were both more complex than that under normal pressure. In addition, when the deviation from the initial set value was small, a slight increase in the purity of the product could be adopted instead of introducing a component controller. The optimal pressure needs to be determined by balancing cost and control. For ethanol-ethyl acetate, the influence of pressure on the dynamic controllability was not obvious, and the optimal pressure can be only determined by economy. The results showed that pressure had different effects on the dynamic controllability of different systems.

Data-Driven Multiobjective Optimization for Burden Surface in Blast Furnace With Feedback Compensation

In this paper, an intelligent data-driven optimization scheme is proposed for finding the proper burden surface distribution, which exerts large influences on keeping blast furnace running smoothly in an energy-efficient state. In the proposed scheme, production indicators prediction models are first developed using a kernel extreme learning machine algorithm. To heel, burden surface decision is presented as a multiobjective optimization problem for the first time and solved by a modified two-stage intelligent optimization strategy to generate the initial setting values of burden surface. Furthermore, considering the existence of the approximation error of the created prediction models, feedback compensation is implemented to enhance the reliability of the results, in which an improved association rule mining method is developed to find the corrected values to compensate the initial setting values. Finally, we apply the proposed optimization scheme to determine the setting values of burden surface using actual data, and experimental results illustrate its effectiveness and feasibility.

Wearable Sleepcare Kit: Analysis and Prevention of Sleep Apnea Symptoms in Real-Time

Obstructive sleep apnea (OSA), although it is a common symptom for ordinary people, is a serious issue in that it can lead to chronic and degenerative brain disease. However, these sleep disorders and apnea symptoms are difficult to diagnose at home or to recognize and cope with severe apnea situations. In response to this, we developed a Sleepcare Kit, an integrated wearable device. The Sleepcare Kit is a wearable distributed system in which the PAAR band and the bio-cradle are combined in the form of a hot plug-in without pre-setting. The PAAR band serves as a gateway for wireless communication with external devices and adjusts initial setting values for various sensors of the bio-cradle. Bio-cradle continuously measures/stores multiple bio-signals (PPG/SPO2, respiration, 3axis-acc, and body temperature) and analyzes the signal data to determine sleep quality and emergency situation in real-time. Although it is a set of small wearable devices, the kit itself diagnoses sleep quality on a real-time base without any external computing assistance while he/she is asleep. Simultaneously, it analyzes the gathered hypopnea and apnea data in real time and calculates the apnea risk phase. Moreover, according to the apnea risk phase, it can inform the wearer or guardian about the danger through the smartphone or smart-speaker. In this paper, we will discuss the algorithm that is used for the detection of sleep apnea in Sleepcare Kit, as well as the software platform for continuous measurement and synchronization of various bio-signals in real time. Moreover, we evaluated the accuracy of the system by comparing the obtained results with the polysomnography equipment used in hospitals.

Implementation of the centralized control system for drone training

Background/Objectives: The drones became a representative item in the IoT era. However, there is no drone pilot test system that can safely train this in the education field. Drones have very dangerous structural problems, so it is very necessary to practice them easily. Therefore, it is necessary to develop a system that can control the drones safely and easily while controlling them.Methods/Statistical analysis: In this paper, we will develop software for controlling a dedicated board platform that can securely perform ground testing by mounting four drones of motor and drive on a board (PCB). To this end, we supported various control IMU (Inertial Measurement Unit) boards for attitude control by using sensor which is the core technology of drone flight control. Also, Acceleration Data, Angular Velocity Data, Earth Magnetic Field Data, and Atmospheric Pressure Data for maintaining the altitude were used for the drone flight.Findings: In the implemented central control system, the AT chip is built in and designed to perform all control related to the flight of the drone. In addition, since it is an embedded system, we have programmed the attitude control using the sensor, the motor output setting, and the controller connection information. The CPU required for drones control can be replaced with various types of controllers besides Fno Arduino, UNO, Muiltiwii. For this purpose, the main PCB is designed so that the power supply terminal can be used for each CPU. Finally, it was developed as a setup program to correct the sensor and output of the drone.Improvements/Applications: The system implemented in this paper can easily control the drone. In addition, acceleration, angular velocity, geomagnetic field, air pressure sensor, GPS, etc. necessary for drone control can be utilized by stabilizing the initial set value. In other words, the zero point of the sensor can be captured and the signal appropriate to the current state of the drone can be stored in the processor.

An Application of the A-PDA Model For the Interconnected Operation Among Adjacent Blocks of Water Distribution Systems In Case of Emergency

The water distribution system is an important social infrastructure providing customers with stable and safe water supply. The fact, however, is that it is not free from various abnormal situations arising from internal / external factors. In case of a water supply failure due to abnormal situations, the emergency interconnected operation between adjacent blocks in the system is one of the most effective countermeasures. To simulate these types of emergency operations, existing hydraulic analysis models, which are based on the infinite water supply assumption, may simulate unrealistic results such as satisfying sufficient water supply for more demand nodes than actual ones. If they want to have more realistic hydraulic simulation result for these situations, it is required to adopt a new hydraulic analysis which is able to consider insufficient water supply for all demand nodes. Demand Driven Analysis (DDA) and Pressure Driven Analysis (PDA) are most commonly used hydraulic analysis. DDA performs a hydraulic analysis based on the assumption that the demand at demand nodes is always 100% satisfied which derives unrealistic results in abnormal situations. In the case of the PDA, it considers the relationship between hydraulic pressure and available flow rate, which is more reliable than the DDA for abnormal operating conditions. However, since DDA and PDA are basis on the infinite water supply assumption, unrealistic hydraulic analysis results may be obtained when they are applied to the insufficient water supply condition such as the emergency interconnected operation between adjacent blocks due to one or more reservoirs may not be working properly. Therefore, Lee et al. (2018) has proposed the Advanced-Pressure Driven Analysis (A-PDA) applying the concept of limited source to the existing PDA. In this study, we apply the PDA and the A-PDA to simulate the hydraulic condition of the emergency interconnected operation between adjacent blocks for a water supply network in Korea and compare the results from them. The target network supplies water to 84,000 households and it consists of 3 reservoirs, 1,492 nodes, 1,937 pipelines, 8 pumps and 10 interconnected emergency pipes. Each reservoir takes responsible for its individual block. When one of the reservoirs cannot supply water to its individual block, the block will be supplied water through the emergency pipes from the adjacent reservoir. Fig 1 shows the layout of target network and Table 1 shows the properties of each reservoir. To explore the effect of the limited water supply condition, we generate an operation scenario: RES1 stops water supply at 00:00hr (mid night) and RES2 and RES3 supply water to Block1 for the emergency. Then, the PDA and the A-PDA are used to simulate this emergency operating condition. The initial water depth of RES2 and RES3 is 3m and 2.7m, respectively. Fig. 2 shows the available supply ratio (ASR, = available demand/required demand) with time by the PDA and the A-PDA for Block1. The ASR with time by the PDA for Block1 show us that emergency water supply to Block1 from RES2 and RES3 can be maintained through the simulation period even though the ASR are 20% to 40%. On the other hand, The ASR with time by the A-PDA for Block1 show us that the emergency water supply to Block1 ceases after 16:00hr. The reason we obtain two different water supply results for Block1 is due to the assumption of the PDA which is that the amount of water supply is unlimited during the simulation period. In the PDA, the water depth of a reservoir is always maintained at the initial set value so that the amount of water demand at demand nodes should be provided. However, for the emergency operating condition we generate for this study, the amount of water from RES2 and RES3 is insufficient to supply water for the entire network without RES1. As shown in Fig. 3, the water depths of RES2 and RES3 are continuously decreased and RES2 is empty at 16:00hr and RES3 is depleted after 39:00hr. After 16:00hr, RES3 is the only water source for the entire network and Block1 cannot be supplied water from RES3 sufficiently. From this simulation results, the A-PDA simulates this type of the water supply situation more realistic than the PDA does since without RES1, obviously, the entire network cannot be provided with sufficient water from RES2 and RES3. Therefore, in the case of the hydraulic analysis which needs to consider water supply quantity such as the interconnection operation required, the application of the A-PDA model is indispensable. Additionally, the application of the A-PDA can anticipate the possible water supply time and the possible emergency interconnected operating time in the abnormal operating condition, which is impossible to obtain by the existing hydraulic analysis. These two values will be used to design or to establish the emergency operating plan for a water supply network for better service quality.

Parameter Identification Methods for Hyperelastic and Hyper-Viscoelastic Models

In this paper, the Ogden model is employed to characterize the hyperelastic properties of rubber, and on the basis of a pattern search algorithm and the Levenberg-Marquardt algorithm, a professional method that can realize the comprehensive fitting of the uniaxial tension, biaxial tension, planar tension, and simple shear experimental data of hyperelastic materials was developed. The experiment data from Treloar (1944) was fitted very well, and the determined parameters by using this method were proven correct and practical in the numerical verification in ANSYS. Then, the constitutive model of the hyper-viscoelastic materials combining the Ogden model with the generalized Maxwell model was explained in detail, and the parameter identification method was also proposed by using the pattern search method. Then, three groups of relaxation tests of uniaxial tension and four groups of simple shear tests with different loading velocities were conducted to obtain the corresponding virtual experiment data. After discussing the constraints and initial setting values for the undetermined parameters, these virtual data of different loading histories were respectively employed to identify the parameters in the hyper-elastic model, and the accuracy and the reliability of the estimated parameters were also verified in ANSYS.

Influence of morphology and crystallinity on field emission properties of NiFe2O4 nanoparticles grown by high-temperature vapor phase condensation route

The nanocrystallites of NiFe2O4 have been successfully synthesized by gas phase condensation using the dc thermal plasma arc method (NF-1) and by the chemical co-precipitation method (NF-2). The field emission studies were carried out on as-synthesized NF-1 and compared with NF-2 nanoparticles. The emission characteristic shows that NF-1 particles have a low turn-on field of 2.3 V μm−1 as compared to NF-2 particles, which have a turn-on field of 3.5 V μm−1. The Fowler–Nordheim plots obtained from the current–voltage characteristics show overall linear behavior as expected from the quantum mechanical tunneling phenomenon. Our results show that both nanoparticles exhibit good emission stability as an emitter without severe deviations from the initial set value. The highly faceted surfaces, along with high crystallinity of NF-1 nanoparticles, is responsible for improved field emission properties than that of NF-2 prepared by the chemical co-precipitation method.

Intelligent Control Framework for the Feeding System in the Biomass Power Plant

This paper proposes an intelligent control framework for biomass drying process with flue gases based on FLC (fuzzy logic controller) and CAN (Controller Area Network) bus. In the operation of a biomass drying process, in order to get the biomass with the set-point low moisture content dried by waste high temperature flue gases, it is necessary to intelligent control for the biomass flow rate. Use of an experiment with varied materials at different initial moisture contents enables acquisition of the biomass flow rates as initial setting values. Set the error between actual straw moisture content and set-point, and rate of change of error as two inputs. the biomass flow rate can be acquired by the fuzzy logic computing as the output. Since the length of dryer is more than twenty meters, the integration by the CAN bus can ensure real-time reliable data acquisition and processing. The control framework for biomass drying process can be applied to a variety of biomass, such as, cotton stalk, corn stalk, rice straw, wheat straw, sugar cane. It has strong potential for practical applications because of its advantages on intelligent providing the set-point low moisture content of biomass feedstock for power generation equipment.

Active Speed Compensation Method of Direct Torque Control System and Stability Analysis

By analyzing characteristics of the DTC (direct torque control) system in electrical driving system, a shortcoming of the classical DTC method is to point out that it is unable to decouple the mutual interference between torque and speed, so that when a running asynchronous motor subjected to an instantaneous impact load, rotor speed and its deviation appears excessive fluctuations that can not be quickly restored to the initial set value. In this research, under conditions that without sensors for measuring load torque and rotor speed, to an electrical drive systems contains DTC devices, a novel ASCC (active speed compensation control) method is proposed based on ADRC (active disturbance rejection control) theory, on account of DTC model of asynchronous motor, a multiobjective observer is designed to regulate both the speed and the torque, and a proof of asymptotic stability that related this new control systems with the observer is made by theoretical deduction. Finally stimulating results show that this method can overcome the shortcomings of classical DTC system and greatly enhance the ability of the high-speed driving system to deal with unexpected impact loads.

Arc plasma synthesized LaB6 nanocrystallite film on various substrates as a field emitter

Lanthanum hexaboride (LaB6) nanocrystallites/nanowires have been successfully synthesized using gas phase condensation in arc plasma. Our results show that the LaB6 nanowires have ~20 nm diameter and length of several micrometers. The as-synthesized LaB6 nanocrystallites and nanowires are crystalline in nature. Field emission studies were carried out on as synthesized LaB6 nano-powder deposited on W and Re tips and foils, and also on Si foil substrates under ultra high vacuum. The Fowler–Nordheim plots obtained from the current–voltage characteristics are found to be linear in accordance with the quantum mechanical tunneling phenomenon. High value of field enhancement factor (8177) is observed for LaB6 on Re substrate, indicating that the electron emission is from the nanometric features of the LaB6. Our results show that the arc plasma synthesized LaB6 nanocrystalline film exhibits good emission stability as emitter without severe deviations from the initial set value and also a strong ability to withstand the ion bombardment, which is useful for low operation voltage vacuum micro/nano electronic devices.

Gas-Liquid flow characterization in bubble columns with various gas-liquid using electrical resistance tomography

Electrical resistance tomography (ERT) is an advanced and new detecting technique that can measure and monitor the parameters of two-phase flow on line, such as gas-liquid bubble column. It is fit for the industrial process where the conductible medium serves as the disperse phase to present the key bubble flow characteristics in multi-phase medium. Radial variation of the gas holdup and mean holdups are investigated in a 0.160 m i. d. bubble column using ERT with two axial locations (Plane 1 and Plane 2). In all the experiments, air was used as the gas phase, tap water as liquid phase, and a series of experiments were done by adding KCl, ethanol, oil sodium, and glycerol to change liquid conductivity, liquid surface tension and viscosity. The superficial gas velocity was varied from 0.02 to 0.2 m/s. The effect of conductivity, surface tension, viscosity on the mean holdups and radial gas holdup distribution is discussed. The results showed that the gas holdup decrease with the increase of surface tension and increase with the increase of viscosity. Meanwhile, the settings of initial liquid conductivity slightly influence the gas holdup values, and the experimental data increases with the increase of the initial setting values in the same conditions.

Sb-doped SnO 2 wire: Highly stable field emitter

Field emission investigations of a single Sb-doped SnO 2 wire synthesized by thermal evaporation have been carried out in conventional field emission geometry under ultrahigh vacuum. An onset field required to draw a current of 1 nA has been reproducibly observed to be 9.5×10 3 V/μm. A current density of 5.88×10 3 A/cm 2 has been drawn with an applied field of 2×10 4 V/μm. The Fowler–Nordheim plot, obtained from the current–voltage ( I– V) measurements, shows linear nature in accordance with the quantum mechanical tunneling phenomenon. The field enhancement factor has been estimated to be 26,500 cm −1, indicating that the emission is from the nanometric features of the Sb-doped SnO 2 wire. The current–time ( I– t) measurement shows high current stability without severe deviations from the initial set value of 1 μA.

Gas pressure regulation in a r.f. ion source

An experimental technique by which devterium gas pressure in a radio frequency ion source is automatically controlled and maintained to its initial set value is described. The accuracy achieved is ± 0.5 µ in about 5 µ gas pressure being used in the r.f. ion source of the neutron generator of this laboratory.