Average Junction Research Articles

Traffic management model for vehicle re-routing and traffic light control based on Multi-Objective Particle Swarm Optimization

In this paper, a novel traffic management model is presented, which simultaneously optimizes vehicle re-routing and traffic light control to alleviate traffic congestion and limit the effects of incidents on traffic flow based on Multi-Objective Particle Swarm Optimization (MOPSO) method. Once a co ngested road is predicted, our proposed Multi-Objective Traffic Light Control is then applied to optimize signal timing which takes the maximization of traffic flow on the edge where the incident takes place and the minimization of the average junction waiting time as two objectives. To improve the performance and sensitivity of MOPSO algorithm, we used Q-Learning algorithm to grant to each agent of the swarm the ability of selecting appropriate MOPSO parameters adapted to the structure of the problem. At the same time, when the situation of the traffic flow starts to become more serious, we adopt a novel Multi-Objective Vehicle Re-routing strategy for assigning alternatives routes to cars before entering the congested road, in order to perform dynamic load balancing. Vehicle re-routing is also optimized by MOPSO to simultaneously find the shortest and least popular path. The obtained results from the simulation using SUMO, a well-known microscopic traffic simulator, confirm the efficiency of the proposed system.

Method for predicting junction temperature distribution in a high-power laser diode bar.

A hybrid experimental/numerical method is proposed for predicting the junction temperature distribution in a high-power laser diode (LD) bar with multiple emitters. A commercial water-cooled LD bar with multiple emitters is used to illustrate and validate the proposed method. A unique experimental setup is developed and implemented first to measure the average junction temperatures of the LD bar emitters. After measuring the heat dissipation of the LD bar, the effective heat transfer coefficient of the cooling system is determined inversely from the numerical simulation using the measured average junction temperature and the heat dissipation. The characterized heat dissipation and effective heat transfer coefficient are used to predict the junction temperature distribution over the LD bar numerically under high operating currents. The results are presented in conjunction with the wall-plug efficiency and the center wavelength shift.

Statistical Thermodynamic Theory of Heat-Induced Gelation of Aqueous Methylated Polyrotaxane Solutions

Chemically modified polyrotaxanes by methylation are water-soluble and show high-temperature gelation in water. To elucidate the molecular mechanism, we developed a theoretical model incorporating the following contributions: hydration–dehydration of cyclic molecules, formation of one-dimensional aggregates composed of a various number of cyclic molecules along the polymer chain, and formation of junction structures by associating between the aggregates. We numerically calculated the sol–gel transition line, the average aggregate length, the average junction multiplicity, the heat capacity change of the solution, the hydration ratio of cyclic molecules, and the translational entropy of cyclic molecules along the chain. We compared our results with the previously reported experimental data, and we discussed the molecular mechanism of the high-temperature gelation and the formation of the junction structures based on the sliding feature of cyclic molecules.

SU‐F‐J‐55: Feasibility of Supraclavicular Field Treatment by Investigating Variation of Junction Position Between Breast Tangential and Supraclavicular Fields for Deep Inspiration Breath Hold (DIBH) Left Breast Radiation

Purpose:To explore the feasibility of supraclavicular field treatment by investigating the variation of junction position between tangential and supraclavicular fields during left breast radiation using DIBH technique.Methods:Six patients with left breast cancer treated using DIBH technique were included in this study. AlignRT system was used to track patient's breast surface. During daily treatment, when the patient's DIBH reached preset AlignRT tolerance of ±3mm for all principle directions (vertical, longitudinal, and lateral), the remaining longitudinal offset was recorded. The average with standard‐deviation and the range of daily longitudinal offset for the entire treatment course were calculated for all six patients (93 fractions totally). The ranges of average ± 1σ and 2σ were calculated, and they represent longitudinal field edge error with the confidence level of 68% and 95%. Based on these longitudinal errors, dose at junction between breast tangential and supraclavicular fields with variable gap/overlap sizes was calculated as a percentage of prescription (on a representative patient treatment plan).Results:The average of longitudinal offset for all patients is 0.16±1.32mm, and the range of longitudinal offset is −2.6 to 2.6mm. The range of longitudinal field edge error at 68% confidence level is −1.48 to 1.16mm, and at 95% confidence level is −2.80 to 2.48mm. With a 5mm and 1mm gap, the junction dose could be as low as 37.5% and 84.9% of prescription dose; with a 5mm and 1mm overlap, the junction dose could be as high as 169.3% and 117.6%.Conclusion:We observed longitudinal field edge error at 95% confidence level is about ±2.5mm, and the junction dose could reach 70% hot/cold between different DIBH. However, over the entire course of treatment, the average junction variation for all patients is within 0.2mm. The results from our study shows it is potentially feasible to treat supraclavicular field with breast tangents.

Relation between grid, channel, and Peano networks in high‐resolution digital elevation models

AbstractThe topological interconnection between grid, channel, and Peano networks is investigated by extracting grid and channel networks from high‐resolution digital elevation models of real drainage basins, and by using a perturbed form of the equation describing how the average junction degree varies with Horton‐Strahler order in Peano networks. The perturbed equation is used to fit the data observed over the Hortonian substructures of real networks. The perturbation parameter, denoted as “uniformity factor,” is shown to indicate the degree of topological similarity between Hortonian and Peano networks. The sensitivities of computed uniformity factors and drainage densities to grid cell size and selected threshold for channel initiation are evaluated. While the topological relation between real and Peano networks may not vary significantly with grid cell size, these networks are found to exhibit the same drainage density only for specific grid cell sizes, which may depend on the selected threshold for channel initiation.

Estimation of the average junction temperature of two phosphors-converted white LED array based on (B + Y + R)/B ratio

The method of non-contact measurement of the junction temperature (Tj) for phosphor-converted white LEDs based on W/B ratio, the ratio of the total radiant energy (W) to the radiant energy of blue emission (B), is verified firstly. It is shown that for two phosphors (Y3Al5O12:Ce and CaAlSiN3:Eu)-converted white LEDs, an significant uncertainty is introduced into the linearity between Tj and W/B ratio. Then a new approach is proposed which uses (B+Y+R)/B ratio, the ratio of the sum of radiant energies of blue emission (B), yellow emission (Y) and red emission (R) to the radiant energy of blue emission, to establish the correlation with Tj. Result shows that the proposed approach is of a satisfactory linearity between Tj and (B+Y+R)/B ratio, with R-square equal to 0.9906 and RMSE equal to 2.27°C. It is also demonstrated that the proposed method is applicable to actual LED lighting system composed of large number of LEDs.

2D SQIF arrays using 20 000 YBCO high Rn Josephson junctions

Superconducting quantum interference filters (SQIFs) have been created using two dimensional arrays of YBCO step-edge Josephson junctions connected together in series and parallel configurations via superconducting loops with a range of loop areas and loop inductances. A SQIF response, as evidenced by a single large anti-peak at zero applied flux, is reported at 77 K for step-edge junction arrays with the junction number N = 1 000 up to 20 000. The SQIF sensitivity (slope of peak) increased linearly with N up to a maximum of 1530 V T−1. Array parameters related to geometry and average junction characteristics are investigated in order to understand and improve the SQIF performance in high temperature superconducting arrays. Initial investigations also focus on the effect of the SQUID inductance factor on the SQIF sensitivity by varying both the mean critical current and the mean inductance of the loops in the array. The RF response to a 30 MHz signal is demonstrated.

Study on the lifetime characteristics of power modules under power cycling conditions

This study presents a study on non-linear accumulative modelling for power module lifetime estimation in non-accelerated operation. The model focuses on solder fatigue based on monitoring the internal thermal resistance of the module. Initially, the relatively small junction temperature variation (ΔT j) cycles contribute little to the lifetime consumption, but with an initial damage the effect becomes noticeable. The original Coffin–Manson accumulation approach is extended for complex mission profiles. The proposed non-linear accumulation model has three aspects: a Coffin–Manson relationship is first established; the thermal resistance degradation is then used to quantify damage accumulation; the effects of the average junction temperature (T jmean) and ΔT j on the rate of degradation are finally included through the parameters of the non-linear accumulation model which also depends on the effect of the present condition of the module. Experiments demonstrate the phenomena and verify the proposed model.

Thermal Characterization of Substrate Options for High-Power THz Multipliers Over a Broad Temperature Range

This paper presents thermal characterization results for three high-power THz Schottky frequency multipliers in the temperature range of 20–380 K. All measured multipliers have different substrates: a 5- $\mu\hbox{m}$ -thick GaAs membrane, a 40- $\mu\hbox{m}$ -thick GaAs substrate, and a 5- $\mu\hbox{m}$ -thick GaAs membrane glued to a 20- $\mu\hbox{m}$ -thick CVD diamond substrate with polymer bonding agent. The thermal characterization results include such parameters as the maximum average junction temperature of the anodes, device total thermal resistance, and device cooling (or heating) times. The results enable designers to better optimize their devices for the maximum power level and temperature range and system engineers to better predict the overall performance of the system in an environment, where the ambient conditions might change. For example, from the thermal resistance point of view the GaAs membrane on diamond substrate clearly outperforms the device on GaAs membrane alone at room temperature or above. However, perhaps surprisingly, at temperatures below 125 K, the GaAs membrane is on par, or even has lower thermal resistance than the membrane on diamond.

Characterization of Boron Diffusion Phenomena According to the Specific Resistivity of N-Type Si Wafer

This paper is directed to characterize the boron diffusion process according to the specific resistivity of the Si wafer. N-type Si wafers were used with the specific resistivity of 0.5-3.2 omega-cm, 1.0-6.5 omega-cm and 2.0-8.0 omega-cm. The boron tribromide (BBr3) was used as boron source to create the PN junction on N-type Si wafer. The boron diffusion in N-type Si wafer was characterized by sheet resistance of wafer surface, secondary ion mass spectroscopy measurements (SIMS) and surface life time analysis. The degree of boron diffusion was depended on the variation in specific resistivity and sheet resistance of the bare N-type Si wafer. The boron diffused N-Si wafer exhibited the average junction depth of 750 nm and boron concentration of 1 x 10(19). N-type Si wafer with the different specific resistance considerably affected the boron diffusion length and life time of Si wafer. It was found that the lifetime of boron diffused wafer was proportional to the sheet resistance and resistivity. However, optimization process may necessary to achieve the high efficiency through the high sheet resistance wafer, because the metallization process control is very sensitive.

Thermal Impedance Measurement on Different Chip Arrangements for Various Multichip LEDs Application

The effect of thermal impedance of three chip arrangements in a multichip light-emitting diode (LED) package has been discussed with each chip attached to a heat sink with thermal interface material. Each orientation represents different existing lighting applications such as T8 tube, MR 16 down light, and spotlight. In this paper, the emitter and sensor current are constantly maintained. One LED of each orientation is driven, while other LEDs are sensed until all LEDs are driven with the emission current of all the orientations. Comparisons are made between the thermal impedance matrix pairs of each LED arrangement to illustrate the difference in the thermal dissipation. Thermal impedance curves show the fluctuation in the thermal flow inside the package, implying the reciprocal behavior of each orientation. This paper further explains the reciprocal behavior of the chips and the importance of the orientation based on junction temperature. Moreover, the principle of linear superposition is implemented to estimate the junction temperature matrix. The theoretical and the experimental results are compared using thermal transient tester. Among three orientations, the square-shaped LED arrangement shows an average junction temperature of 116 °C within the package while exerting the highest change of junction temperature of 4 °C, comparing with the linear superposition method.

Evolution of nano-junctions in piezoresistive nanostrand composites

When nickel nanostrands (NiNs) are embedded inside of highly flexible silicone, the silicone becomes an extremely piezoresistive sensor capable of measuring a large dynamic range of strains. These sensors experience an increase in conductance of several orders of magnitude when strained to 40% elongation. It has been hypothesized that this effect stems from a net change in average junction distance between the conductive particles when the overall material is strained. The quantum tunneling resistance across these gaps is highly sensitive to junction distance, resulting in the immense piezoresistive effect. In this paper, the average junction distance is monitored using dielectric spectroscopy while the material is strained. By incorporating new barrier height measurements of the base silicone material from a nanoindentation experiment, this experiment validates previous assumptions that, on average, the junctions between NiNs decrease while the sample is strained, instigating the large piezoresistive effect. The nature of the material’s response to strain is explored and discussed.

Improving Power Converter Reliability: Online Monitoring of High-Power IGBT Modules

The real-time junction temperature monitoring of a high-power insulated-gate bipolar transistor (IGBT) module is important to increase the overall reliability of power converters for industrial applications. This article proposes a new method to measure the on-state collector-emitter voltage of a high-power IGBT module during converter operation, which may play a vital role in improving the reliability of the power converters. The measured voltage is used to estimate the module average junction temperature of the high and low-voltage side of a half-bridge IGBT separately in every fundamental cycle of the current by calibrating them at load current. The measurement is very accurate and also measures the voltage at the middle of a pulse-width modulation (PWM) switching. A major objective is that this method is designed to be implemented in real applications. The performance of this technique is measured in a wind power converter at a low fundamental frequency. To illustrate more, the test method as well as the performance of the measurement circuit are also presented. This measurement is also useful to indicate failure mechanisms such as bond wire lift-off and solder layer degradation. The measurements of and rise in the junction temperature after five million cycles of normal operation of the converter are also presented.

Comparison between Thermal Interface Materials Made of Nano Carbon Tube (NCT) with Gad Pad 2500 in Term of Junction Temperature by Using CFD Software, Fluent<sup>TM</sup>

This paper presents the comparison between thermal interface materials made of nano carbon tube (NCT) with Gad Pad 2500 in term of junction temperature by using CFD Software, FluentTM. 3D model of electronic packaging is built using GAMBIT and simulated using FLUENT software. The study was made for a microprocessors arranged in line under different types of inlet velocities and package (chip) powers. The results are presented in terms of average junction temperature when chip powers have been increased from 0.5 W to 2 W. The junction temperature is been observed and it was found that the junction temperature of the electronic packaging using nano carbon has lower junction temperature compare to the Gad Pad 2500. It also found that the NCT was able to reduce the junction temperature up to 20-30% compare to others thermal interface material.

Simulation of Nano Carbon Tube (NCT) in Thermal Interface Material for Electronic Packaging Application by Using CFD Software

This paper presents the nanocarbon tube in thermal interface material for electronic packaging application by using three dimensional numerical analysis of heat and fluid flow in computer. 3D model of electronic packaging is built using GAMBIT and simulated using FLUENT software. The study was made for a microprocessors arranged in line under different types of inlet velocities and package (chip) powers. The results are presented in terms of average junction temperature when chip powers have been increased from 2 W to 5 W. The junction temperature is been observed and it was found that the junction temperature of the electronic packaging using nanocarbon was able to wind stand the increasing in chip power from 2 W until 5 W. It also found that the material selection play important roles to control and manage the junction temperature. The strength of CFD software in handling heat transfer problems is proved to be excellent.

Supine Craniospinal Irradiation Using a Proton Pencil Beam Scanning Technique Without Match Line Changes for Field Junctions

To propose and validate a craniospinal irradiation approach using a proton pencil beam scanning technique that overcomes the complexity of the planning associated with feathering match lines. Ten craniospinal irradiation patients had treatment planned with gradient dose optimization using the proton pencil beam scanning technique. The robustness of the plans was evaluated by shifting the isocenter of each treatment field by ±3 mm in the longitudinal direction and was compared with the original nonshifted plan with metrics of conformity number, homogeneity index, and maximal cord doses. An anthropomorphic phantom study using film measurements was carried out on a plan with 5-cm junction length. To mimic setup errors in the phantom study, fields were recalculated with isocenter shifts of 1, 3, 5, and 10 mm longitudinally, and compared with the original plans and measurements. Uniform dose coverage to the entire target volumes was achieved using the gradient optimization approach with averaged junction lengths of 6.7 ± 0.5 cm. The average conformity number and homogeneity index equaled 0.78 ± 0.03 and 1.09 ± 0.01, respectively. Setup errors of 3 mm per field (6 mm in worst-case scenario) caused on average 4.6% lower conformity number 2.5% higher homogeneity index and maximal cord dose of 4216.1 ± 98.2 cGy. When the junction length was 5 cm or longer, setup errors of 6 mm resulted in up to 12% dosimetric deviation. Consistent results were reached between film measurements and planned dose profiles in the junction area. Longitudinal setup errors directly reduce the dosimetric accuracy of the proton craniospinal irradiation treatment with matched proton pencil beam scanning fields. The reported technique creates a slow dose gradient in the junction area, which makes the treatment more robust to longitudinal setup errors compared to conventional feathering methods.

Effects of Oxygen Doping on the Transport Properties of Hg<sub>0.82</sub>Re<sub>0.18</sub>Ba<sub>2</sub>Ca<sub>2</sub>Cu<sub>3</sub>O<sub>8+d</sub> Superconducting Polycrystals

Hg0.82Re0.18Ba2Ca2Cu3O8+dpolycrystalline ceramic samples were prepared using a solid-vapour reaction technique. First, the ceramic precursor was prepared from a mixture of Ba2Ca2Cu3Oxand ReO2powders in a molar ratio of 1:0.18. The precursor material was annealed under three different partial pressures of oxygen that consisted of a mixture of oxygen/argon in the following ratios: 5/95 (sample A), 10/90 (sample B) and 15/85 (sample C). Secondly, the precursors prepared at different O2partial pressures were blended with HgO at a molar relationship of 1:0.82. The synthesis was carried out at 865 °C for 72 h. Moreover, analyses using X-ray powder diffraction, Scanning Electron Microscopy (SEM), and Energy Dispersion X-ray spectroscopy (EDS) were performed. These results demonstrated a similarity in the grain morphology within the samples. Using SEM images, a histogram of grain-boundary size was produced where the average junction size is represented by a gamma density distribution function. Finally, the samples were submitted to ac electrical resistivity ρ (T) under a low applied magnetic field (up to 400 Oe). Samples cut into bars approximately 7 × 1 × 1 mm3in size were studied using a four-probe technique. The zero-resistance critical temperatures (Tcj) were determined from ρ (T) curves. The results are compared and qualitatively explained in the framework of flux trapping by superconducting grains. In our opinion, the oxygen partial pressure has a strong influence on the grain junctions and causes island structures that form defects at the grain boundaries.

An investigation on piezoresistive behavior of carbon nanotube/polymer composites: II. Positive piezoresistive effect

Due to the diversity of carbon nanotubes (CNTs), polymers, and the preparation processes of the composites, CNT-filled polymeric composites present various piezoresistive properties. One puzzling issue is the concurrence of a negative piezoresistive effect and a positive piezoresistive effect in composites with different polymer matrixes. In this paper, we present a microscopic view of the nature of the positive piezoresistive effect and its dependence on the polymer matrix types based on the model in our previous study, in which the piezoresistive behavior was tailored by a parameter—the average junction gap variation (AJGV)—describing the statistical property of the CNT conductive network. The microscopic movement process of CNTs embedded in a polymer matrix was analyzed and then the Poisson’s ratio of the polymer matrix was determined as a key factor that is in charge of negative or positive piezoresistive properties. The obstacle effect of polymer chains on the movement of CNTs was also found to be responsible for the positive piezoresistive effect as it affects the AJGV in compressive strain. Based on numerical simulations of CNT network deformation with different Poisson’s ratios and minimum junction gaps caused by the obstacle effect, the positive piezoresistive effect was found resulted from the obstacle effect on CNT junction gap variations that exceeds the initial value of the AJGV caused by the CNT network deformation, and only occur under the precondition of the polymer matrixes with a large Poisson’s ratio close to 0.5. The conclusions were then verified experimentally using composites with two kinds of polymer matrixes with significantly different Poisson’s ratios.

A study on IGBT junction temperature (Tj) online estimation using gate-emitter voltage (Vge) at turn-off

A novel method is presented for online estimation of the junction temperature (Tj) of semiconductor chips in IGBT modules, based on evaluating the gate-emitter voltage (Vge) during the IGBT switch off process. It is shown that the Miller plateau width (in the Vge waveform) depend linearly on the junction temperature of the IGBT chips. Hence, a method can be proposed for estimating the junction temperature even during converter operation – without the need of additional thermal sensors or complex Rth network models. A measurement circuit was implemented at gate level to measure the involved time duration and its functionality was demonstrated for different types of IGBT modules. A model has been proposed to extract Tj from Vge measurements. Finally, an IGBT module with semiconductor chips at two different temperatures has been measured using Vge method and this method was found to provide the average junction temperature of all the semiconductor chips.

SU-E-T-621: Analysis of Robustness of Proton Pencil Beam Scanning Technique for Delivery of Craniospinal Irradiation

Purpose: To investigate the robustness and safety of craniospinal irradiation (CSI) planned with a proton pencil beam scanning (PBS) technique which overcomes the complexity of the planning associated with feathering match lines. Methods: Six CSI patients were planned with gradient-dose matching using PBS technique. Uniform dose coverage to the entire target volumes was achieved with averaged junction lengths of 6.9±0.3 cm. Robustness of the plans was evaluated by shifting the isocenter of each treatment field by ±3 mm in longitudinal direction and compared with the original non-shifted plan with metrics of conformity number (CN) and homogeneity index (HI). An anthropomorphic phantom study using film measurements was also carried out on a plan with 5 cm junction length. Results: For a given junction length, the dose errors were directly proportional to the setup errors. Setup errors of 3 mm from each field caused on average 3.5% lower CN and 2.1% higher HI. Minimal D95% to PTV and D98% to CTV were reduced by 2.2%±1.5% and 2.8%±1.7% respectively. A drop of maximal 6.8%±5.5% on the minimal dose to the cribriform plate was also observed. When the junction length was 5cm or longer, these 3mm setup errors from each field resulted in up to 12% dose errors. Consistent results were reached between film measurements and planned dose profiles in the junction area. Due to near-zero exit doses beyond the target volume, sparing of anterior organs such as heart, liver, lung and kidney were observed. Conclusions: Longitudinal setup errors directly reduce the dosimetric accuracy of the CSI treatment with matched proton fields. The reported technique creates a slow dose gradient in the junction area, which makes the treatment more robust and safe to longitudinal setup errors compared to conventional feathering methods.