Design of a 2.4 GHz High-Performance Up-Conversion Mixer with Current Mirror Topology

In this paper, a low voltage low power up-conversion mixer, designed in a Chartered 0.18 μm RFCMOS technology, is proposed to realize the transmitter front-end in the frequency band of 2.4 GHz. The up-conversion mixer uses the current mirror topology and current-bleeding technique in both the driver and switching stages with a simple degeneration resistor. The proposed mixer converts an input of 100 MHz intermediate frequency (IF) signal to an output of 2.4 GHz radio frequency (RF) signal, with a local oscillator (LO) power of 2 dBm at 2.3 GHz. A comparison with conventional CMOS up-conversion mixer shows that this mixer has advantages of low voltage, low power consumption and high-performance. The post-layout simulation results demonstrate that at 2.4 GHz, the circuit has a conversion gain of 7.1 dB, an input-referred third-order intercept point (IIP3) of 7.3 dBm and a noise figure of 11.9 dB, while drawing only 3.8 mA for the mixer core under a supply voltage of 1.2 V. The chip area including testing pads is only 0.62×0.65 mm2

Practical stability and controllability for nonlinear discrete time-delay systems

In this paper we study the practical asymptotic stability for a class of discrete-time time-delay systems via Razumikhin-type Theorems. Further estimations of the solution boundary and arrival time of the solution are also investigated based on practical stability. In addition, the proposed theorems are used to analyze the practical controllability of a general class of nonlinear discrete systems with input time delay. Some easy testing criteria for the uniform practical asymptotical stability are derived via Lyapunov function and Razumikhin technique. Finally a numerical example is given to illustrate the effectiveness of the proposed results

Pengaruh zikir terhadap kesihatan mental dan tekanan psikologi dalam mendepani cabaran revolusi industri 4.0

Revolusi Industri 4.0 (IR4) telah memberi implikasi negatif terhadap kesihatan mental dan psikologi dalam masyarakat seperti kemurungan, kebimbangan dan tekanan perasaan. Masalah-masalah ini mampu diatasi dengan amalan zikir sebagai terapi psikospiritual berunsur kerohanian Islam. Kajian ini berbentuk kualitatif dengan menggunakan kaedah temu bual separa-berstruktur serta analisis secara deduktif, induktif dan tematik untuk mengetahui kesan sebelum dan selepas berzikir secara berjemaah. Pendekatan Lataif Qur’aniyyah digunakan untuk memaknakan kedudukan al-zikr dan pengamalannya lebih meluas. Peserta-peserta majlis zikir bulanan dalam kajian ini terdiri daripada 83 orang dan diadakan di Kediaman Rasmi Menteri Besar Selangor. Hasil kajian menunjukkan ‘zikir bersanad’ yang diamalkan secara konsisten merupakan santapan rohani terbaik dalam mempengaruhi jiwa dan emosi individu ke arah celik akal yang menjadi matlamat kemuncak dalam kaunseling. Hal ini berkesan dalam membantu perubahan minda dan tingkah laku manusia dalam pembentukan keluarga dan masyarakat yang bersahsiah dan harmoni. Justeru, zikir yang bersanad, yakni dalam bimbingan bersama guru rohani (Mursyid), dengan fokus niat untuk mencapai ‘keterhubungan kerohanian’ dengan Nabi Muhammad (s.a.w.) dan ‘jiwa fakir’ kepada Allah (s.w.t.), serta memenuhi adab-adab dan syarat-syarat takwa adalah terapi psikospiritual yang mujarab dalam merawat pelbagai masalah mental

The effect of comorbid attention-deficit/hyperactivity disorder symptoms on face memory in children with autism spectrum disorder: Insights from transdiagnostic profiles

Face memory impairments are common but heterogeneous in autism spectrum disorder (ASD), which may be influenced by co-occurrence with attention-deficit/hyperactivity disorder (ADHD). Here, we aimed to investigate the phenotype change of face memory in children with ASD comorbid ADHD symptoms, and discuss the potential role of executive function (EF). Ninety-eight children were analyzed in the present study, including ASD- (ASD-only, n = 24), ADHD (n = 23), ASD+ (with ADHD symptoms, n = 23) and neurotypical controls (NTC, n = 28). All participants completed two tests: face encoding and retrieving task and Wisconsin Card Sorting Test (WCST) for measuring face memory and EF, respectively. Results revealed that: compared with the NTC group, children with ASD- exhibited lower accuracy in both face encoding and retrieving, and participants with ASD+ showed lower accuracy only in the retrieving, whereas no differences were found among participants with ADHD. Moreover, in the ASD+ group, face encoding performance was correlated with response perseverative errors (RPE) and failure to maintain sets (FMS) of WCST; significantly, there were no group differences between ASD+ and NTC in these two indices. The transdiagnostic profiles indicated that comorbid ADHD symptoms could modulate the face encoding deficiency of ASD, which may be partially compensated by EF. Shared and distinct intervention strategies to improve social cognition are recommended for children undergoing treatment for each condition

The long-term effects of alfalfa on soil water content in the Loess Plateau of northwest China

Soil desiccation is the most serious problem in forest vegetations and grassland, which lead to widespread land degradation in the Loess Plateau of China. The soil water variations at 0 to 1000 cm depth of different vegetations were studied to explore the hydrological effects of vegetations and determine the optimal length of alfalfa (Medicago sativa L.) phase at the Zhenyuan Agri-ecological Station of the Loess Plateau in China. Eight treatments were designed in this study: waste land, wheat land and six continuous growing alfalfa treatments, including 4-year-old (4 year), 6-year-old (6 year), 8- year-old (8 year), 12-year-old (12 year), 18-year-old (18 year) and 26-year-old (26 year) alfalfa grasslands.  Results showed that the wheat field had the best soil water content and no dry soil layer, while slightly dry soil layer occurred in wasteland and 4, 6 and 8 year alfalfa grasslands. After alfalfa grew for > 8 years, moderately dry soil layer appeared in the grassland and expanded beyond 500 cm soil depth. The result also showed that wheat field, wasteland and the alfalfa grasslands growing for 4, 6 and 8 years had no unfavorable impacts on the ecological environments of the soil moisture but the grasslands for 12, 18 and 26 years did exert relatively stronger unfavorable influences on the hydrological effects. Considering all the factors, this study recommends that the optimal length of alfalfa phase should be 8 years.Key words: Different vegetation, alfalfa grasslands, soil water content, ecological effect, soil desiccation, Loess Plateau of China