10 Gbit/s modulation of 1.3 µm GaInNAs lasers up to 110°C

Maximum power point tracking (MPPT) enables extracting the maximum power that a photovoltaic panel is capable of delivering regardless of the change in solar irradiance or ambient temperature throughout the day, maximizing its efficiency; it is carried out by means of the control of a DC-DC converter to modify the voltage delivered to the load, such that the variation in the current keeps the power constant. In this work it is designed and simulated an MPPT with an SEPIC converter whose pulse width control signal is determined by the Perturb & Observe (P&O) algorithm to identify the voltage that produces the maximum power, it is available at the output of a BUCK converter controlled by a PID that enables energizing loads with constant voltage despite of the variations produced by the P&O algorithm. The will be energized from a 30 W panel and will charge 9 V batteries at a constant charge voltage, that are commonly used in the robotics club of the Universidad Politécnica Salesiana, located in Quito, Ecuador. Matlab/Simulink is used for simulation considering scenarios of variable irradiance levels and also load variations. The results show a good transient response of the SEPIC converter with the MPPT control to extract the maximum power, moreover the PID c ontroller enables attenuating the ripple obtaining a constant output with a ripple of 2.5%, and does not generate overshoot.KeywordsBatteryConverterPhotovoltaicMPPTPIDSubsystem

An improved resistance-based thermal model for prismatic lithium-ion battery charging

The sensitivity and specificity analyses of ambient temperature and population size on the transmission rate of the novel coronavirus (COVID-19) in different provinces of Iran

Start-up modes of thermoelectric generator based on vehicle exhaust waste heat recovery

Compared with the traditional plug-in charging system, the wireless charging system for battery charging has broad application prospects due to its significant advantages, such as security, convenience, and aesthetics. In practical applications, in order to prolong the battery lifecycles, it is preferred to charge the battery with constant current (CC) and constant voltage (CV) modes. However, since the battery equivalent resistance varies greatly during charging, it is not easy to design a complete charging system owning CC and CV output characteristics. Besides, the equivalent input impedance of the system is preferably resistive to improve efficiency and enhance power transfer capability; therefore, achieving the zero phase angle (ZPA) operation is extremely important. Hence, a novel three-coil structure WPT system is proposed in this paper to solve the above issues. A comprehensive theoretical analysis for the three-coil system to realize the CC and CV charging modes with perfect ZPA operation at two fixed operating frequencies is presented. Furthermore, due to the parasitic losses of passive components and the instability of the dc input voltage, it is unrealistic to achieve accurate and stable CC and CV outputs through the inherent properties of the circuit itself. Consequently, a simple closed-loop controller is introduced into the system to enable the desired CC and CV charging characteristics with zero voltage switching (ZVS) operation by slightly adjusting the operating frequency. Finally, a confirmatory experimental prototype with 4.6-A charging current and 56-V charging voltage is fabricated to confirm the feasibility and validity of the proposed method. The experimental results agree well with the theoretical analysis.

An equivalent circuit model for Vanadium Redox Batteries via hybrid extended Kalman filter and Particle filter methods

Fecal immunochemical tests (FITs) are widely used in colorectal cancer (CRC) screening, but hemoglobin degradation, due to exposure of the collected sample to high temperatures, could reduce test sensitivity. We examined the relation of ambient temperature exposure with FIT positivity rate and sensitivity. This was a retrospective cohort study of patients 50 to 75 years in Kaiser Permanente Northern California's CRC screening program, which began mailing FIT kits annually to screen-eligible members in 2007. Primary outcomes were FIT positivity rate and sensitivity to detect CRC. Predictors were month, season, and daily ambient temperatures of test result dates based on US National Oceanic and Atmospheric Administration data. Patients (n = 472,542) completed 1,141,162 FITs. Weekly test positivity rate ranged from 2.6% to 8.0% (median, 4.4%) and varied significantly by month (June/July vs December/January rate ratio [RR] = 0.79, 95% confidence interval [CI], 0.76 to 0.83) and season. FIT sensitivity was lower in June/July (74.5%; 95% CI, 72.5 to 76.6) than January/December (78.9%; 95% CI, 77.0 to 80.7). FITs completed during high ambient temperatures had lower positivity rates and lower sensitivity. Changing kit design, specimen transportation practices, or avoiding periods of high ambient temperatures may help optimize FIT performance, but may also increase testing complexity and reduce patient adherence, requiring careful study.

Issue Highlights

Valve-regulated lead-acid (VRLA) batteries that have aged on a float charge at constant voltage occasionally suffer from thermal runaway. Operating conditions for a VRLA battery have been simulated by changing the electrolyte saturation level in the separator and the ambient temperature. The charge current, battery temperature and cell overpressure were measured during current-limited constant-voltage charging. The experiments show that applied voltage, saturation level and ambient temperature are significant variables in the oxygen cycle. However, the saturation level of the electrolyte in the separator pore volume is critical. When it is lower than 80%, thermal runaway occurs readily. Significant corrosion of the positive grid and poor conductivity between the grid and the active mass (AM) is also found in aged VRLA batteries, and many inactive PbSO4 crystals appear on the negative plates. As a result, both positive and negative plates have a very high resistance, which can accelerate thermal runaway.

This paper presents a constant temperature and constant voltage (CT-CV) based charging technique applied to a Nickel Manganese Cobalt (NMC) 18650 and lithium-ion cells. Analysis and behavior of the cell at different ambient temperature have been investigated in this paper. Moreover, the experimental procedure details, including the implemented CT-CV algorithm for analyzing the charging of batteries are detailed. The proposed CT-CV charging is compared with existing constant current and constant current (CC-CV) under different ambient temperatures and charging current rates. Finally, experimental validations are performed on NCM batteries and the results are presented.

A specific on-board electronic system has been developed for driving the infra red source calibration of the balloon-borne Olimpo. This system operates at ambient temperature, whereas the source is located on the 2K stage of the cryostat. This electronic system first generates a heating signal on the iridium strip of the source, and then monitors the source temperature stability by several measurements of an NbSi thermometer which is located under the source. Priority in the design was to achieve a high stability measurement, with low heating perturbations of the source, and with a large temperature range of the electronics. The design merges a modulated bias system, with a low noise voltage differential amplifier, and a digital acquisition. The whole system is driven by a microcontroller whose algorithm was optimized to minimize the noise perturbations. Electronic components have been selected for their large temperature operation range, and for their low temperature sensitivity. Moreover, the electronic system is designed to compensate the thermal deviation of the components. The system has been tested successfully with simulated and real IR source for several temperatures. With 600 pW of total sensor dissipation injected during 40 ms, the measurement standard deviation achieved for the resistive value of a 10 k/spl Omega/ thermometer reaches 0.5 /spl Omega/ (48 ppm). Moreover the sensitivity of the electronic for the measurement is of 25 ppm//spl deg/C ranging from -60/spl deg/C to +20/spl deg/C, in agreement with the specifications.

A novel FPI with hollow core taper structure for strain and inclination measurements

We designed the optimum Si optical modulator (Si-MOD) structure with applying p-type-doped strained SiGe. By applying the strained Si70Ge30 layer, about twice larger optical modulation efficiency in VπL can be obtained in the simulation. In case of a relaxed Si70Ge30 layer, enhancement factor in VπL decrease to about 50%, but optical loss is comparable to that without a SiGe layer. We demonstrated a high modulation efficiency of 0.67 Vcm, which is about 50% more efficient than that of Si-MODs with just a lateral pn junction. From the Raman spectra and SIMS analyses, Ge composition of SiGe was estimated to be around 35%. Crystalline strain of SiGe was estimated to be 1.7% on the 0.04 mm2 square pattern, which is comparable to the theoretical value. On the other hand, it was estimated to be 1.1% for the selective growth of SiGe on the Si WG with a lateral pn junction. Therefore, biaxial strain of SiGe was a little relaxed, because the selective growth of SiGe pattern has a large aspect ratio with 400 nm width and 800 μm length. The Si-MOD showed 27.3 GHz bandwidth at -3 Vdc with 200μm-long phase-shifter. We demonstrated eye diagrams of NRZ (non-return-to-zero) 40 Gbps of 231-1 PRBS (pseudorandom binary sequence) and PAM (pulse amplitude modulation)-4 40Gbps at 1.3 μm wavelength under the condition of differential RF drive with 1.6-2.0 Vpp at -2Vdc. The optical loss of the Si-MOD is estimated to be 1.0-1.5 dB/mm, which is comparable to that of simulation. With increase in temperature up to 80℃, optical loss increased by about 0.3-0.5 dB, which would originate from band-gap shrinkage of a strained-SiGe layer. We obtained the clear eye diagram at 25 Gbps with 27-1 PRBS from the optical transceiver chip when the CMOS-driver output voltage was 0.9 Vpp and Vdc was -0.3V. ER (extinction ratio) of about 2 dB was obtained in case of 800μm-long phase shifter with 4-divided electrodes. We also studied a high-speed and high-efficiency of surface-illumination type Ge photodetector (Ge-PD) with a 1800 nm thick Ge layer. By optimizing the anti-reflection coating stack structure, high responsivity of 0.8-0.9 A/W was uniformly obtained within the wafer. At 3 Vdc, about 15 GHz bandwidth was obtained. In case of the Ge-PD with thick Ge-layer, photo-carrier transit time mainly limits the frequency bandwidth. Therefore, we optimized the layered structure of Ge thickness on SOI to satisfy the high-responsivity and high-bandwidth. We demonstrated an output waveform from integrated CMOS-TIA (trans-impedance amplifier) at 25 Gbps with 27-1 PRBS at 1.3 μm wavelength at 3.3 Vdc. Clear eye opening was obtained, which would contribute to the efficient optical interconnect.

Optical modulators for optical interconnects require a small size, small voltage, high speed and wide working spectrum. For this purpose, we developed Si slow-light Mach-Zehnder modulators via a 180 nm complementary metal-oxide-semiconductor process. We employed 200 μm lattice-shifted photonic crystal waveguides with interleaved p-n junctions as phase shifters. The group index spectrum of slow light was almost flat at ng ≈ 20 but exhibited ±10% fluctuation over a wavelength bandwidth of 20 nm. The cutoff frequency measured in this bandwidth ranged from 15 to 20 GHz; thus, clear open eyes were observed in the 25 Gbps modulation. However, the fluctuation in ng was reflected in the extinction ratio and bit-error rate. For a stable error-free operation, a 1 dB margin is necessary in the extinction ratio. In addition, we constructed a device with varied values of ng and confirmed that the extinction ratio at this speed was enhanced by larger ng up to 60. However, this larger ng reduced the cutoff frequency because of increased phase mismatch between slow light and radio frequency signals. Therefore, ng available for 25 Gbps modulation is limited to up to 40 for the current device design.

The exploration of novel nitrogen-rich heterocyclic building blocks is of importance in the field of energetic materials. A series of 2-(1,2,4-triazole-5-yl)-1,3,4-oxadiazole derivatives based on a new energetic skeleton have been first synthesized by a simple synthetic strategy. All three compounds are well-characterized by IR spectroscopy, NMR spectroscopy and thermal analysis. The compounds 5 and 8 are further characterized by single-crystal X-ray diffraction analysis. 8 and its salts (8a-8c) possess relative high decomposition temperature and low sensitivity, while 5 exhibits low decomposition temperature and high sensitivity. According to EXPLO5 calculation results of detonation performance, both 5 and 8 display acceptable detonation velocities (D) of 8450 m/s and 8130 m/s and detonation pressures (P) of 31.6 GPa and 29.2 GPa, respectively. Furthermore, 5 containing a rare diazonium ylide structure shows high impact sensitivity (4.5 J), making it has a potential as a primary explosive.