•A helically twisted elliptic (HTE) cylinder based on biomimetic is considered.•The forced convection around the HTE cylinder is originally investigated.•The effect of Re on the flow around the HTE ...cylinder is initially researched.•The local Nu identifies the effect of the HTE geometry on the heat transfer.
The present study is an original research for the forced convection heat transfer around a helically twisted elliptic (HTE) cylinder inspired by a daffodil stem. Also, this study is an initial investigation to find the effect of the Reynolds number (Re) in the laminar flow regime. We carried out numerical simulations to investigate the flow and heat transfer around the HTE cylinder in 60⩽Re⩽150 and Prandtl number (Pr) of 0.7. The circular cylinder is considered for the purpose of the comparison. The drag and lift fluctuation for the HTE cylinder are much smaller than those of the smooth cylinder. The decreasing rate of Strouhal number (St) for the HTE cylinder to that for the smooth cylinder is about 4–7% in the present Reynolds number range. The smaller St of the HTE cylinder than the smooth cylinder associate a longer vortex formation length of the HTE cylinder. The three-dimensional (3D) geometry of the HTE cylinder formed the spanwise variation of the Nusselt number (Nu), resulting in the sinusoidal profiles. This spanwise variation of the Nusselt number is identified by the flow structures and the isotherms distribution. The time- and total surface-averaged Nusselt number of the HTE cylinder decreases from about 1.2% to 2.8% in the present HTE configuration and Re range, compared to the smooth cylinder.
The Photovoltaic properties of dye co-sensitized solar cells fabricated by using a one-bath mixed dye solution were compared with those of mono-sensitized devices. Co-sensitized TiO
2
...photo-electrodes were prepared from a mixed dye solution of M-Red 2-cyano-3(10-hexthyl-phenothiazin)acrylic acid or D-Red 3,3′-hexyl-bis(phenothiazine-2-cyanoacrylic acid) and S-Blue (5-carboxy-3,3-dimethyl-1-nonyl-indolium)methylene-2-(E)-(5-carboxy-3,3-dimethyl-1-octylindolin-2-ylidene)-3-oxocyclobut-1-enolate) to improve the short-circuit current (J
sc
) of dyesensitized solar cells (DSSCs). When the photo-electrode was co-sensitized from the mixed solution of M-Red (75%) and S-Blue (25%), the power conversion efficiency (PCE) of the resulting DSSCs exhibited an 11.2% increase, compared to that of M-Red dye (100%). Use of the mixed dye solution of M-red and S-Blue is thought to have ability to reduce the aggregation of S-Blue dye adsorbed on TiO2 surface, leading to an enhancement in J
sc
of the co-sensitized solar cells. In the case of D-Red dye, the co-sensitized device prepared from the mixed solution of D-Red (50%) and S-Blue (50%) dye showed a 31.7% enhancement in the PCE, compared to that of the solar cell with a mono (D-Red)-sensitized photo-electrode. Unlike the co-sensitization system using the mixed solution of M-Red and S-Blue, the optimum photovoltaic performance was found from the mixed solution with a 1:1 ratio (D-Red:S-Blue). This could be attributed to the adsorption rate of D-Red (dimeric red) being faster than that of M-Red (monomeric red) dye, there inducing similar adsorption rates for the D-Red and the S-blue dye in the one-bath adsorption process for co-sensitization.
•Cu-doped Bi2Te2.7Se0.3 was first synthesized by using Cu nanoparticle precursor.•The power factor is enhanced by the substitutional Cu doping in quintuple layers.•Substantial reduction of electronic ...thermal conductivity originates from Cu doping.•Average zT value at 300–500 K for 2% Cu–Bi2Te2.7Se0.3 increased to 0.79.•The power generation efficiency can be enhanced by 25% from the pristine sample.
Bi-Te-based materials have been used for room-temperature thermoelectric applications. However, n-type Bi2(Te,Se)3 thermoelectric alloys show a limited conversion efficiency, as compared to their p-type counterparts, thus hindering further widespread room-temperature applications. In this study, we investigated the enhanced thermoelectric properties of n-type Bi2(Te,Se)3 materials by the addition of Cu nanoparticles via a conventional high-energy ball milling process. The electrical and thermal transport properties were modulated by changing the amount of Cu nanoparticles. The power factor was enhanced by controlling the carrier, and the total thermal conductivity was reduced mainly due to the reduction in electronic thermal conductivity. Thus, dimensionless thermoelectric figure of merit (zT) at room temperature was enhanced for the Cu-added samples, and the highest zT value of 0.85 at 375 K was achieved in 2% Cu-doped Bi2Te2.7Se0.3. The average zT (zTavg) value between room temperature and 500 K was 0.79 for the 2% Cu-doped Bi2Te2.7Se0.3, which was 20% higher than that of the pristine Bi2Te2.7Se0.3, whereas a zT higher than 0.80 was sustained from room temperature to ~450 K. These results can lead to a high thermoelectric power generation efficiency of 7.6% at ΔT = 200 K.
In the present study, we assessed the bactericidal effect of a combination of blue light (BL) and riboflavin (Rb) and elucidated the bacterial inactivation mechanism. Higher Rb concentrations ...(0.005–50 μM) resulted in greater inactivation of Escherichia coli O157:H7 and Salmonella Typhimurium suspended in phosphate buffer saline (PBS). In the present dose-dependent study, significant inactivation was observed following BL + Rb treatment at 30 J/cm2 (19 min 23 s) in PBS. In apple juice (pH 3.2), BL + Rb treatment resulted in a 3–4-log reduction in the pathogens at 30 J/cm2. As expected, ROS was the key factor for pathogen inactivation. Moreover, cell membrane damage was observed on propidium iodide (PI) uptake analysis and transmission electron microscopy (TEM). These results indicated that BL + Rb treatment can be used as a powerful intervention system to ensure microbial safety in liquid beverages, in addition to enhancing the nutritional value.
•Combined treatment of blue LED and riboflavin achieved synergistic effect (2–3 log).•ROS generation was the significant factor of bacterial inactivation.•Cell membrane damage and deactivated enzyme induced the improvement of cell death.•Microbial safety and nutritional enhancement can be fulfilled with the BL + Rb.
This paper presents a direct photon-counting X-ray image detector with a HgI 2 photoconductor for high-quality medical imaging applications. The proposed sampling-based charge preamplifier with ...asynchronous self-reset enables a pixel to detect single X-ray photon energy with higher sensitivity and faster processing rate. The use of the correlated double sampling enabled by the sampling-based architecture also reduces flicker noise and contributes to the achievement of high pixel-to-pixel uniformity. Discrimination of the energy level of the detected X-rays is performed by the proposed compact in-pixel ADC with low power consumption. Three 15-bit counters in each pixel count up energy-discriminated photons for the reconstruction of multispectral X-ray images. A 128 × 128 X-ray image detector with a pixel size of 60 × 60 μm 2 is implemented and measured using a 0.13-μm/0.35-μm standard CMOS process. It discriminates 3 energy levels of photon energy with a gain of 107 mV/ke - and a static power consumption of 4.6 μW/pixel. The measured equivalent noise charge (ENC) and minimum detectable energy level of the detector pixel are 68 e - rms and 290 e - , respectively. The measured maximum threshold dispersion in the pixel array is 164 e - rms without any calibration. The functionality of our chip is also successfully demonstrated using real X-ray images.
Bioaerosols, including infectious diseases such as COVID-19, are a continuous threat to global public safety. Despite their importance, the development of a practical, real-time means of monitoring ...bioaerosols has remained elusive. Here, we present a novel, simple, and highly efficient means of obtaining enriched bioaerosol samples. Aerosols are collected into a thin and stable liquid film by the unique interaction of a superhydrophilic surface and a continuous two-phase centrifugal flow. We demonstrate that this method can provide a concentration enhancement ratio of ∼2.4 × 106 with a collection efficiency of ∼99.9% and an aerosol-into-liquid transfer rate of ∼95.9% at 500 nm particle size (smaller than a single bacterium). This transfer is effective in both laboratory and external ambient environments. The system has a low limit of detection of <50 CFU/m3 air using a straightforward bioluminescence-based technique and shows significant potential for air monitoring in occupational and public-health applications.
To verify the interface state properties of amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) with SiN x and SiO 2 gate dielectrics, the low-frequency noise (LFN) of various ...gate-length devices from 5 to 50 μm was measured and evaluated. Before LFN measurements, the dc characteristics, such as the subthreshold slope ( S ), were measured for comparison. The interface state density ( N it ) extracted by S for an a-IGZO TFT with SiN x gate dielectrics is only 1.3 times higher than that for an a-IGZO TFT with SiO 2 gate dielectrics. However, the trap density ( Nt ) extracted by LFN for an a-IGZO TFT with SiN x gate dielectrics is almost 80 times higher than that for one with SiO 2 gate dielectrics. Moreover, carrier number fluctuations are the dominant mechanism for LFNs in an a-IGZO TFT with SiN x gate dielectrics. This large difference between SiN x and SiO 2 gate dielectrics in LFN measurement is related to the fast degradation of a-IGZO TFTs with SiN x gate dielectrics by the bias temperature instability or light illumination.
This article presents a fully integrated multi-phase (MP) buck converter for on-chip power management units. A peak-and-valley differential sensing (PVDS) scheme based on a flying capacitor is ...proposed to evenly balance the multiple inductor currents without significant power overhead even under mismatches in inductances, parasitic series resistances, and control-signal skews among phases. In addition, dynamic re-allocation of on-chip capacitors enables an even more optimal frequency response and output ripple based on the number of activated phases. It also improves the chip area efficiency, resulting in a higher power density. The proposed DLL-based MP clock generation provides high granularity in the phase-shedding control to achieve high efficiency over a wide load range. The proposed fully integrated buck converter using six bond-wire inductors (1 nH) was fabricated in a 28-nm CMOS process. The chip running at a frequency of 400 MHz/phase can finely adjust the number of active phases by an integer step ranging from 1 to 6 through sensing a load current. A maximum power density of 1.23 W/mm2 and a peak efficiency of 83.7% were measured. This work achieved an ultra-fast dynamic voltage scaling (DVS) rate of 75 mV/ns.
