New facility for primary calibration of differential spectral responsivity of solar cells using LDLS-based monochromatic source

A newly established setup for primary calibration and characterization of solar cells at NMCC/SASO is presented. This differential spectral responsivity (DSR) measurement instrument uses laser-driven light source (LDLS)-based modulated (AC) source to measure the spectral responsivity of photovoltaic (PV) detectors and solar cells. The setup is intended for measuring the spectral responsivity in the wavelength range from 250 nm to 2000 nm, bias level up to 1.5 kW/m2, with which a measurement uncertainty of 1.06 % (k = 2, in the range of 300 nm to 900 nm) could be achieved. We present validation measurements as well as spectral responsivity and external quantum efficiency (EQE) measurements of reference solar cells to demonstrate the objective of the setup. We present a preliminary evaluation of the associated uncertainty components as well as an uncertainty budget for validation, optimization and standardization of our setup.

Bias-induced impedance effect of the current-carrying conductors

<p class="Abstract">The paper presents the previously unstudied properties of current-carrying conductors utilising impedance spectroscopy. The purpose of the article is to present discovered properties that are the significant context of impedance research. The methodology is based on the superposition of test signals and bias affecting the objects under study. These are the main results obtained in this work: the studied objects have an additional low-frequency impedance during the passage of an electric current; the bias-induced impedance effect (Z_BI-effect) is noticeably manifested in the range of 0.01 Hz … 100 Hz and it has either capacitive or inductive nature or both types, depending on the bias level (current density) and material types. The experiments in this work were done using open and covered wires made of pure metals, alloys, and non-metal conductors, such as graphite rods. These objects showed the Z_BI-effect that distinguishes them from other objects, such as standard resistors of the same rating, in which this phenomenon does not occur. The Z_BI-effect was modeled by equivalent circuits. Particular attention is paid to assessing the consistency of experimental data. Understanding the nature of this effect can give impetus to the development of a new type of instrument in various fields.</p>

Ultrasound for Breast Cancer Detection Globally: A Systematic Review and Meta-Analysis

PURPOSE Mammography is not always available or feasible. The purpose of this systematic review and meta-analysis is to assess the diagnostic performance of ultrasound as a primary tool for early detection of breast cancer. MATERIALS AND METHODS For this systematic review and meta-analysis, we comprehensively searched PubMed and SCOPUS to identify articles from January 2000 to December 2018 that included data on the performance of ultrasound for detection of breast cancer. Studies evaluating portable, handheld ultrasound as an independent detection modality for breast cancer were included. Quality assessment and bias analysis were performed with the Quality Assessment of Diagnostic Accuracy Studies-2 tool. Sensitivity analyses and meta-regression were used to explore heterogeneity. The study protocol has been registered with the international prospective register of systematic reviews (PROSPERO identifier: CRD42019127752). RESULTS Of the 526 identified studies, 26 were eligible for inclusion. Ultrasound had an overall pooled sensitivity and specificity of 80.1% (95% CI, 72.2% to 86.3%) and 88.4% (95% CI, 79.8% to 93.6%), respectively. When only low- and middle-income country data were considered, ultrasound maintained a diagnostic sensitivity of 89.2% and specificity of 99.1%. Meta-analysis of the included studies revealed heterogeneity. The high sensitivity of ultrasound for the detection of breast cancer was not statistically significantly different in subgroup analyses on the basis of mean age, risk, symptoms, study design, bias level, and study setting. CONCLUSION Given the increasing burden of breast cancer and infeasibility of mammography in certain settings, we believe these results support the potential use of ultrasound as an effective primary detection tool for breast cancer, which may be beneficial in low-resource settings where mammography is unavailable.

Controlling the Q-Point in Distributed Feedback Lasers Using a Numerical Optimization Methodology

In this paper, a new methodology for controlling the Q-point in the distributed feedback (DFB) lasers is proposed. The method based on reducing the DFB transient period (TP) by optimizing laser’s model parameters numerically. The analysis has taken into account investigated the effects of the laser injection current (Iinj), the dc-bias level (Ibias), the temperature (T) variation, and the gain compression factor (ε). Results showed that by optimizing the value of Iinj, Ibias, T and ε; the Q-point could be controlled effectively. Where increasing the current ratio (i.e., Iinj/Ith) leads to reduce the TP value. In addition, by increasing Iinj and/or Ibias, the relaxation oscillation period (TRO) and the laser delay time (TDelay) are reduced significantly. From the other hand, the temperature varying may push the DFB laser to operate in an improper region through increasing the TP value; which may lead it to operate in the off-mode. Moreover, as ε is increased, the sinusoidal oscillations are dramatically damped results in a reduction in the TRO value and larger period of stabilized.

Comparison of DCO-OFDM, ADO-OFDM, HDC-OFDM and HNC-OFDM for Optical Wireless Communications

This paper presents a new form of orthogonal frequency division multiplexing (OFDM) termed as hybrid noise cancelled asymmetrically clipped optical OFDM (HNC-OFDM) for optical wireless communication. This HNC-OFDM is formed by combining the concepts of noise cancelled asymmetrically clipped optical OFDM and DC biased optical OFDM (DCO-OFDM). HNC-OFDM has the same bit error rate (BER) performance and dimming flexibility but less complexity compared to the recently developed hybrid diversity combined OFDM. The optimum DC bias level for HNC-OFDM, DCO-OFDM and asymmetrically clipped DC biased optical OFDM is shown to depend on the target BER, the constellation size, the received signal to noise power ratio, the proportion of DCO-OFDM element, the link type, equalization, etc. Simulations results show that with an optimum bias, HNC-OFDM can outperform others in an average power limited channel, while DCO-OFDM is a better choice for a peak power limited channel.

Judgments under emotioncy’s influence

Following a number of studies on discovering the controlling dormant forces in linguistic biases, this study attempts to introduce the concept of emotioncy as a driving force in explicating the causes of prejudice manifested through biases in speech. To this end, two scales for measuring individuals’ bias and their emotioncy levels were devised and validated through Rasch measurement. A total number of 341 participants were asked to take the scales. Afterward, structural equation modeling (SEM) was employed to investigate the probable relationships between sub-constructs of the scales. The results indicated that as individuals’ emotioncy level increases, the bias level decreases. In other words, involvement slides people toward being less judgmental and thus less biased in language, while exvolvement leads people toward using more abstract words, and therefore more biased language. In the end, implications of the findings were discussed in the realm of judgment and decision making.

Patient results and laboratory test accuracy

Purpose – Traditional quality control materials used for monitoring the clinical laboratory test accuracy might be non-commutable with patient samples and may not detect systematic errors. The aim of this paper is to describe a method to monitor inter-instrument bias using result distributions that are independent of the control's commutability. Design/methodology/approach – Serum calcium data collected within a laboratory network were assessed. A reference interval was calculated using a computerized, indirect Hoffmann's algorithm using all data across a laboratory network without excluding any results. Results outside the reference interval were considered as the zero-bias distribution. Three allowable bias levels were then calculated to determine the corresponding shift in abnormal results for each bias level in both directions from the zero-bias distribution. The observed result distributions in three laboratories within the network were compared for bias performance after one year of the reference interval study. Findings – Performance levels for bias were: minimum allowable <1.27 percent; desirable <0.85 percent; and optimal <0.42 percent. Zero bias result distribution above and below the reference interval for calcium was 3.92 percent and 2.53 percent respectively. All three laboratories performed within the desirable allowable bias level. Originality/value – Bias-monitoring process using patient result distributions allows managers to: assess systematic error between laboratory instruments; improve laboratory quality control; and strengthen patient risk management.

Electron and Hole Trap Signal with Similar Defect Parameters in Chalcopyrite Based Solar Cells

Copper chalcopyrite based solar cells with different molar gallium to gallium plus indium ratio (GGI) are looked at, using deep level transient spectroscopy (DLTS) and admittance spectroscopy (AS). Depending on the respective measurement parameters, like reverse bias level, height and length of the voltage pulse applied, either a minority carrier or/and a majority carrier deep level signal is/are detected in the temperature range below 200 K. The AS investigations reveal only one trap signal. After a detailed description of the defect properties taking advantage of the two diode model, we discuss the origin of these trap signals in view of our experimental findings

Effect of bias in ferroelectric-antiferroelectric relaxation

The ferroelectric-antiferroelectric transition in greyscale generation of antiferroelectric liquid crystal displays (AFLC) is a heterogeneous process. The process has been described as the growth of finger-like domains [1]. We have previously studied the ferroelectric-antiferroelectric phase transition, relaxation that follows the data pulse in surface stabilized asymmetric antiferroelectric liquid crystal displays using biasless video frequency waveforms [2]. This relaxation involves an intensity decay of the light transmitted by a pixel and depends on several parameters such as surface stabilization, rotational viscosity of the AFLC, magnitude of the data pulse, and bias voltage.The usual multiplexed driving of AFLC displays leads to long-term stabilisation of the grey levels induced by the data pulses within the selection time. However, depending on the bias level, alternative greyscale mechanisms may be obtained by allowing the grey levels to decay during the frametime. These greyscales may be advantageous in some instances since they improve the dynamic response of the AFLC device and reduce the reset time of the waveform.In this study we extend the previous work to include the effect of bias. We present the measured data, in terms of growth pattern and speed and present an extension of the previously model on order to explain the results.