Validating SMPS-measured size distribution of double-mode spherical Silica nanoparticles by Transmission Electron Microscope (TEM)

A nanoparticles size is one of their key physical characteristics that can affect their fate in a human’s respiratory tract (in case of inhalation) and also in the environment. Hence, measuring the size distribution of nanoparticles is absolutely essential and contributes greatly to their characterization. For years, Scanning Mobility Particle Sizers (SMPS), which rely on measuring the electrical mobility diameter of particles, have been used as one of the most reliable real-time instruments for the size distribution measurement of nanoparticles. Despite its benefits, this instrument has some drawbacks, including equivalency problems for non-spherical particles (i.e. assuming a non-spherical particle is equal to a spherical particle of diameter d due to the same electrical mobility), as well as limitations in terms of its use in workplaces, because of its large size and the complexity of its operation...

Autonomous operation of multiple interconnected microgrids with self-healing capacity

This paper shows how multiple interconnected microgrids can operate in autonomous mode in a self–healing medium voltage network. This is possible if based on network self– healing capability, the neighbour microgrids are interconnected and a surplus generation capacity is available in some of the Distributed Energy Resources (DERs) of the interconnected microgrids. This will reduce or prevent load shedding within the microgrids with less generation capacity. Therefore, DERs in a microgrid are controlled such that they share the local load within that microgrid as well as the loads in other interconnected microgrids. Different control algorithms are proposed to manage the DERs at different operating conditions. On the other hand, a Distribution Static Compensator (DSTATCOM) is employed to regulate the voltage. The efficacy of the proposed power control, sharing and management among DERs in multiple interconnected microgrids is validated through extensive simulation studies using PSCAD/EMTDC.

Control, operation and power sharing among parallel converter-interfaced DERs in a microgrid in the presence of unbalanced and harmonic loads

This paper demonstrates power management and control of DERs in an autonomous MG. The paper focuses on the control and performance of converter-interfaced DERs in voltage controlled mode. Several case studies are considered for a MG based on the different types of loads supplied by the MG (i.e. balanced three-phase, unbalanced, single-phase and harmonic loads). DERs are controlled by adjusting the voltage magnitude and angle in their converter output through droop control, in a decentralized concept. Based on this control method, DERs can successfully share the total demand of the MG in the presence of any type of loads. This includes proper total power sharing, unbalanced power sharing as well as harmonic power sharing, depending on the load types. The efficacy of the proposed power control, sharing and management among DERs in a microgrid is validated through extensive simulation studies using PSCAD/EMTDC.

A phase-locked-loop design for the smooth operation of a hybrid microgrid

A microgrid contains both distributed generators (DGs) and loads and can be viewed by a controllable load by utilities. The DGs can be either inertial synchronous generators or non-inertial converter interfaced. Moreover, some of them can come online or go offline in plug and play fashion. The combination of these various types of operation makes the microgrid control a challenging task, especially when the microgrid operates in an autonomous mode. In this paper, a new phase locked loop (PLL) algorithm is proposed for smooth synchronization of plug and play DGs. A frequency droop for power sharing is used and a pseudo inertia has been introduced to non-inertial DGs in order to match their response with inertial DGs. The proposed strategy is validated through PSCAD simulation studies.

Dynamics of mode transitions in inductively-coupled plasmas

The dynamics of transitions between the electrostatic and electromagnetic discharge modes of the low-frequency (460 kHz) inductively coupled plasma (LF ICP) reactor is studied. A series of images of plasma glows in Ar and N2 gases taken in the process of continuous variation of the input power confirms the discharge bistability and hysteresis. The operation regimes and parameters making the LF ICP reactor attractive for materials synthesis and processing applications are discussed.

Power transfer and mode transitions in low-frequency inductively coupled plasmas

Operation and mode jumps in low-frequency (500 kHz) radio-frequency inductively coupled plasmas are investigated. The discharge is driven by a flat inductive coil which can excite the electrostatic (E) and electromagnetic (H) discharge modes. The power transfer efficiency and mode transition behavior are studied. It is found that the power reflection coefficient as a function of the input power is minimal in the vicinity of the mode transitions and exhibits hysteresis, which is also observed when the operating gas pressure is varied.

Low-frequency, high-density, inductively coupled plasma sources : operation and applications

Operation regimes, plasma parameters, and applications of the low-frequency (∼500 kHz) inductively coupled plasma (ICP) sources with a planar external coil are investigated. It is shown that highly uniform, high-density (ne∼9×1012 cm-3) plasmas can be produced in low-pressure argon discharges with moderate rf powers. The low-frequency ICP sources operate in either electrostatic (E) or electromagnetic (H) regimes in a wide pressure range without any Faraday shield or an external multipolar magnetic confinement, and exhibit high power transfer efficiency, and low circuit loss. In the H mode, the ICP features high level of uniformity over large processing areas and volumes, low electron temperatures, and plasma potentials. The low-density, highly uniform over the cross-section, plasmas with high electron temperatures and plasma and sheath potentials are characteristic to the electrostatic regime. Both operation regimes offer great potential for various plasma processing applications. As examples, the efficiency of the low-frequency ICP for steel nitriding and plasma-enhanced chemical vapor deposition of hydrogenated diamond-like carbon (DLC) films, is demonstrated. It appears possible to achieve very high nitriding rates and dramatically increase micro-hardness and wear resistance of the AISI 304 stainless steel. It is also shown that the deposition rates and mechanical properties of the DLC films can be efficiently controlled by selecting the discharge operating regime.

Nanoparticle emissions from a fleet of CNG buses in transient and steady state operation

Particle emission measurements from a fleet of 14 CNG and 5 Diesel buses were measured both for transient and steady state mode s on a chassis dynamometer with a CVS dilution system. Several transient DT80 cycles and 4 steady sate modes (0, 25, 50 100% of maximum load) were measured for each bus tested. Particle number concentration data was collected by three CPC’s (TSI 3022, 3010 3782WCPC) having D50 cut-offs set to 5, 10 and 20nm respectively. The size distributions were measured with a TSI 3080 SMPS with a 3025 CPC during the steady state modes. Particle mass emissions were measured with a TSI Dustrak. Particle mass emissions for Diesel buses were upto 2 orders of magnitude higher than for CNG buses. Particle number emissions during steady state modes for Diesel busses were 2 to 5 times higher than for CNG busses for all of the tested loads. On the other hand for the DT80 transient cycle particle number emissions were up to 3 times higher for the CNG buses. More detailed analysis of the transient cycles revealed that the reason for this was due to high particle number emissions from CNG busses during the acceleration parts of the cycles. Particles emitted by the CNG busses during acceleration were in the nucleation mode with the majority being smaller than 10nm. Volatility measurements have also shown that they were highly volatile.

Wide area control of SVCs for first swing stabilisation and damping in longitudinal systems

A non-linear Kalman filter based control strategy for SVCs located in major load groups is presented. This focusses on the limitation and damping of inter-area modes. It does this through treating local modes as noise and uses a tunable nonlinear control algorithm to improve both first swing stability and system damping. Simulation on a four machine system shows that the Kalman filer can successfully lock on to a desired inter-area mode and obtain a 31% improvement in critical clearing time as well as improved damping.

Compensation for higher order mode coupling between inclined coupling slots and radiating slots in planar slotted waveguide arrays

Summary form only given. Geometric simplicity, efficiency and polarization purity make slot antenna arrays ideal solutions for many radar, communications and navigation applications, especially when high power, light weight and limited scan volume are priorities. Resonant arrays of longitudinal slots have a slot spacing of one-half guide wavelength at the design frequency, so that the slots are located at the standing wave peaks. Planar arrays are implemented using a number of rectangular waveguides (branch line guides), arranged side-by-side, while waveguides main lines located behind and at right angles to the branch lines excite the radiating waveguides via centered-inclined coupling slots. Planar slotted waveguide arrays radiate broadside beams and all radiators are designed to be in phase.

Relationships between maternal overweight prior to pregnancy, feeding mode and infant feeding beliefs and practices

Aim To examine whether pre-pregnancy weight status was associated with maternal feeding beliefs and practices in the early post-partum period. Methods Secondary analysis of longitudinal data from Australian mothers. Participants (N=486) were divided into two weight status groups based on self-reported pre-pregnancy weight and measured height: healthy weight (BMI <25kg/m2; n=321) and overweight (BMI>25kg/m2; n=165). Feeding beliefs and practices were self-reported via an established questionnaire that assessed concerns about infant overeating and undereating, awareness of infant cues, feeding to a schedule, and using food to calm. Results Infants of overweight mothers were more likely to have been given solid foods in the previous 24hrs (29% vs 20%) and fewer were fully breastfed (50% vs 64%). Multivariable regression analyses (adjusted for maternal education, parity, average infant weekly weight gain, feeding mode and introduction of solids) revealed pre-pregnancy weight status was not associated with using food to calm, concern about undereating, awareness of infant cues or feeding to a schedule. However feeding mode was associated with feeding beliefs and practices. Conclusions Although no evidence for a relationship between maternal weight status and early maternal feeding beliefs and practices was observed, differences in feeding mode and early introduction of solids was observed. The emergence of a relationship between feeding practices and maternal weight status may occur when the children are older, solid feeding is established and they become more independent in feeding.

A new twist on mode indicator functions

Mode indicator functions (MIFs) are used in modal testing and analysis as a means of identifying modes of vibration, often as a precursor to modal parameter estimation. Various methods have been developed since the MIF was introduced four decades ago. These methods are quite useful in assisting the analyst to identify genuine modes and, in the case of the complex mode indicator function, have even been developed into modal parameter estimation techniques. Although the various MIFs are able to indicate the existence of a mode, they do not provide the analyst with any descriptive information about the mode. This paper uses the simple summation type of MIF to develop five averaged and normalised MIFs that will provide the analyst with enough information to identify whether a mode is longitudinal, vertical, lateral or torsional. The first three functions, termed directional MIFs, have been noted in the literature in one form or another; however, this paper introduces a new twist on the MIF by introducing two MIFs, termed torsional MIFs, that can be used by the analyst to identify torsional modes and, moreover, can assist in determining whether the mode is of a pure torsion or sway type (i.e., having a rigid cross-section) or a distorted twisting type. The directional and torsional MIFs are tested on a finite element model based simulation of an experimental modal test using an impact hammer. Results indicate that the directional and torsional MIFs are indeed useful in assisting the analyst to identify whether a mode is longitudinal, vertical, lateral, sway, or torsion.

A do-it-yourself (DIY) switched mode power conversion laboratory

In the education of physical sciences, the role of the laboratory cannot be overemphasised. It is the laboratory exercises which enable the student to assimilate the theoretical basis, verify the same through bench-top experiments, and internalize the subject discipline to acquire mastery of the same. However the resources essential to put together such an environment is substantial. As a result, the students go through a curriculum which is wanting in this respect. This paper presents a low cost alternative to impart such an experience to the student aimed at the subject of switched mode power conversion. The resources are based on an open source circuit simulator (Sequel) developed at IIT Mumbai, and inexpensive construction kits developed at IISc Bangalore. The Sequel programme developed by IIT Mumbai, is a circuit simulation program under linux operating system distributed free of charge. The construction kits developed at IISc Bangalore, is fully documented for anyone to assemble these circuit which minimal equipment such as soldering iron, multimeter, power supply etc. This paper puts together a simple forward dc to dc converter as a vehicle to introduce the programming under sequel to evaluate the transient performance and small signal dynamic model of the same. Bench tests on the assembled construction kit may be done by the student for study of operation, transient performance and closed loop stability margins etc.

Feeding mode of Australian infants in the first 12 months of life: An assessment against national breastfeeding indicators

Background: In 2011, Australia published a set of 6 population-level indicators assessing breastfeeding, formula use, and the introduction of soft/semisolid/solid foods. Objectives: This study aimed to report the feeding practices of Australian infants against these indicators and determine the predictors of early breastfeeding cessation and introduction of solids. Methods: Mother–infant dyads (N = 1470) were recruited postnatally in 2 Australian capital cities and regional areas of 1 state between February 2008 and March 2009. Demographic and feeding intention data were collected by self-completed questionnaire at infant birth, with feeding practices (current feeding mode, age of breastfeeding cessation, age of formula and/or solids introduction) reported when the infant was between 4 and 7 months of age, and around 13 months of age. Multiple logistic regression was used to determine the predictors of breastfeeding cessation and solids introduction. Results: Although initiation of breastfeeding was almost universal (93.3%), less than half of the infants were breastfed to 6 months (41.7%) and 33.3% were receiving solids by 4 months. Women who were socially disadvantaged, younger, less educated, unpartnered, primiparous, and/or overweight were most likely to have ceased breastfeeding before 6 months of age, and younger and/or less educated women were most likely to have introduced solid food by 4 months of age. Not producing adequate milk was the most common reason provided for cessation of breastfeeding. Conclusion: The feeding behaviors of Australian infants in the first 12 months fall well short of recommendations. Women need anticipatory guidance as to the indicators of breastfeeding success and the tendency of women to doubt the adequacy of their breast milk supply warrants further investigation.

Forgery attacks on ++AE authenticated encryption mode

In this paper, we analyse a block cipher mode of operation submitted in 2014 to the cryptographic competition for authenticated encryption (CAESAR). This mode is designed by Recacha and called ++AE (plus-plus-ae). We propose a chosen plaintext forgery attack on ++AE that requires only a single chosen message query to allow an attacker to construct multiple forged messages. Our attack is deterministic and guaranteed to pass ++AE integrity check. We demonstrate the forgery attack using 128-bit AES as the underlying block cipher. Hence, ++AE is insecure as an authenticated encryption mode of operation.