Meningkatkan Hasil Belajar Siswa pada Materi Pewarisan Sifat melalui Pembelajaran Direct Instruction di SMP

: This study aims to determine the learning outcome model through direct instruction . This research is a classroom action research by providing research on the subject of action in two cycles of learning . Subjects in this study were students of class IX A SMP Negeri 1 Ledo academic year 2014/2015 . The data collection used observation sheet teaching practices and student achievement test cycle I and II . The results showed that the direct learning model of instruction in the material of heredity can increase the average value of learning outcomes in the first cycle of 63.7 and the second cycle of 72. The learning process of the two cycles have increased as much as 85

On the Optimization of Iterative Clipping and Filtering for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) offers spectral efficiency advantage, however, it is limited by peak-to-average power (PAPR) problem. The PAPR can be reduced using iterative clipping and filtering (ICF) scheme but requires that the same signals are iteratively clipped with a fixed clipping threshold at different clipping iterations. This method warrants that fast-Fourier transform (FFT)/inverse FFT (IFFT) blocks must be driven in the order of iterations many times to attain a desired PAPR threshold which expends the system power and expands the processing time. Using a second-order cone program, the number of iterations required to attain the desired PAPR threshold was reduced. This optimized ICF (OICF) was later simplified using Lagrange multiplier (LM). In this paper, we apply an adaptive clipping threshold to the LM scheme to improve the performance of the simplified OICF (SOICF). Our results show significant reduction of the PAPR problem compared with the earlier SOICF scheme albeit with some degradation in the bit error ratio (BER) performance that can be under 1.0 dB depending on the chosen clipping threshold. In addition, we also illustrate the results of the performances and the theoretical relationships between the error vector magnitude (EVM) and PAPR, between clipping ratio (CR) and EVM, and lastly the inter-dependencies of EVM, PAPR, the number of OFDM subcarriers, and the CR

An Enhanced Nonlinear Companding Scheme for Reducing PAPR of OFDM Systems

A new companding scheme for reducing the peak-to-average power ratio (PAPR) of orthogonal frequency-division multiplexing (OFDM) systems is proposed in this study. It proceeds from speech signal processing similar to the earliest μ -law companding (MC) model. The proposed scheme compands (compresses and expands) the amplitudes of OFDM signals to a maximum of 1 V. Besides significantly reducing the PAPR, the proposed technique is also able to function as a limiter, thus reducing the system complexity and limiting the amplitudes of OFDM symbols to a unity maximum voltage, which does not exist in other companding PAPR techniques. Over frequency-selective fading channels with frequency domain equalization and using minimum mean square error (MMSE) to minimize the noise overhead, the proposed technique outperforms four other companding schemes over light and severe fading conditions. Finally, we demonstrate that PAPR reduction using companding can dispense with corresponding decompanding scheme at the receiver as it amplifies the distortion noise, thereby reducing the bit error ratio performance and increasing the receiver complexity. We investigate the out-of-band interference of the proposed scheme and also show that it outperforms the other existing techniques by up to 5 dB

Precoding of correlated symbols for STBC systems design

© ICST Institute for Computer Sciences, Social Informatics and Telecommunications Engineering 2017. A problem with transmitting correlated symbols over multiple transmit channel paths is that there is no diversity gain achieved at the receiver. Precoding technique provides a smart approach to achieving diversity gains at the receiver even when correlated symbols are transmitted; by phase variation, amplitude variation or both provided by the precoder. The space-time block code (STBC) technique, for example, is well-known when transmitting the same symbols by making them appear as different symbols using conjugation. We observe that correlated symbols can be transmitted over multiple transmit channel paths over STBC scheme while still achieving diversity. The correlated symbols can be made to appear as different symbols by using precoders; this enables diversity and improves data rate. Combining the proposed with the equivalent channel matrix (EVCM) permits the proposed design to outperform the conventional precoding of uncorrelated symbols technique by 2 dB at all bit error ratio (BER) for 2 × 1 and 2 × 2 antenna configurations. This is useful in increasing data rates with better BER performance

Agile gravitational search algorithm for cyber-physical path-loss modelling in 5G connected autonomous vehicular network

Based on the characteristics of the 5 G standard defined in Release 17 by 3GPP and that of the emerging Beyond 5 G (or the so-called 6 G) network, cyber-physical systems (CPSs) used in smart transport network infrastructures, such as connected autonomous vehicles (CAV), will significantly depend on the cellular networks. The 5 G and Beyond 5 G (or 6 G) will operate over millimetre-wave (mmWave) bands. These network standards require suitable path loss (PL) models to guarantee effective communication over the network standards of CAV. The existing PL models suffer heavy signal losses and interferences at mmWave bands and may not be suitable for cyber-physical (CP) signal propagation. This paper develops an Agile Gravitational Search Algorithm (AGSA) that mitigates the PL and signal interference problems in the 5G–NR network for CAV. On top of that, a modified Okumura-Hata model (OHM) suitable for deployment in CP terrestrial mobile networks is derived for the CAV-CPS application. These models are tested on the real-world 5 G infrastructure. Results from the simulated models are compared with measured data for the modified, enhanced model and four other existing models. The comparative evaluation shows that the modified OHM and AGSA performed better than existing OHM, COST, and ECC-33 models by 90%. Also, the modified OHM demonstrated reduced signal interference compared to the existing models. In terms of optimisation validation, the AGSA scheme outperforms the Genetic algorithm, Particle Swarm Optimisation, and OHM models by at least 57.43%. On top of that, the enhanced AGSA outperformed existing PL (i.e., Okumura, Egli, Ericson 999, and ECC-33 models) by at least 67%, thus presenting the potential for efficient service provisioning in 5G-NR driverless car applications

Low-Power Wide Area Network Technologies for Internet-of-Things: A Comparative Review

The rapid growth of Internet-of-Things (IoT) in the current decade has led to the the development of a multitude of new access technologies targeted at low-power, wide area networks (LP-WANs). However, this has also created another challenge pertaining to technology selection. This paper reviews the performance of LP-WAN technologies for IoT, including design choices and their implications. We consider Sigfox, LoRaWAN, WavIoT, random phase multiple access (RPMA), narrow band IoT (NB-IoT) as well as LTE-M and assess their performance in terms of signal propagation, coverage and energy conservation. The comparative analyses presented in this paper are based on available data sheets and simulation results. A sensitivity analysis is also conducted to evaluate network performance in response to variations in system design parameters. Results show that each of RPMA, NB-IoT and LTE-M incurs at least 9 dB additional path loss relative to Sigfox and LoRaWAN. This study further reveals that with a 10% improvement in receiver sensitivity, NB-IoT 882 MHz and LoRaWAN can increase coverage by up to 398% and 142% respectively, without adverse effects on the energy requirements. Finally, extreme weather conditions can significantly reduce the active network life of LP-WANs. In particular, the results indicate that operating an IoT device in a temperature of -20∘C can shorten its life by about half; 53% (WavIoT, LoRaWAN, Sigfox, NB-IoT, RPMA) and 48% in LTE-M compared with environmental temperature of 40C

Root-Based Nonlinear Companding Technique for Reducing PAPR of Precoded OFDM Signals

Orthogonal frequency division multiplexing (OFDM) signals are characteristically independent and identically distributed Gaussian random variables that follow Rayleigh distribution. The signals also exhibit high peak-toaverage power ratio (PAPR) problem due to the infinitesimal amplitude component distributed above the mean of the Rayleigh distribution plot. Since the amplitudes are nonlinearly and non-monotonically increasing, applying roots to the amplitude distribution is shown in this work to change the probability density function (PDF) and thus reduces the PAPR. We exemplify these by imposing this constraint on standard μ-law companding (MC) technique in reducing PAPR of OFDM signals which is known to expand the amplitudes of low power signals only without impacting the higher amplitude signals. This limits the PAPR reduction performance of the MC scheme. Since companding involves simultaneously compressing/expanding high/low amplitude OFDM signals respectively, in this study, we refer to the new method as a root-based MC (RMC) scheme that simultaneously expands and compresses OFDM signal amplitudes unlike MC. In addition, we express a second transform independent of the MC model. The results of the two proposed schemes outperform four other widely used companding techniques (MC, log-based modified (LMC), hyperbolic arc-sine companding (HASC) and exponential companding (EC)). Besides these, we precode the OFDM signals using discrete Hartley Transform (DHT) in order to further reduce the PAPR limits achieved by RMC by distorting the phase. While preserving the BER, DHT-precoded RMC outperforms all four other companding schemes (MC, EC, HASC, LMC) in terms of PAPR

Impacts des effluents liquides industriels sur l’environnement urbain d’Abidjan - Côte D’Ivoire

Au cours de ces dernières années, les pouvoirs publics ivoiriens ont fait de l’industrialisation l’un des maillons essentiels du développement, après le succès de l’agriculture. Mais la mise en oeuvre de cette politique pose parfois des problèmes d’environnement à Abidjan. La présente étude a pour objectif principal d’évaluer à travers six paramètres (T °C, pH, DCO, DBO5, MES et MGT), les impacts environnementaux négatifs des effluents industriels dans le milieu urbain d’Abidjan. Pour ce faire, des analyses physico-chimiques de 36 échantillons de rejets industriels, ont été réalisées. A l’exception du pH et de la température, les valeurs extrêmes des paramètres de pollution (DCO, DBO5, MES et MGT respectivement de 1392,83 mg O2/l, 910,03 mg O2/l, 231,53 mg/l et 332,67 mg/l) sont largement supérieures à la norme ivoirienne. Ce qui indique que la zone urbaine d’Abidjan est polluée. Par ailleurs, l’activité industrielle a favorisé aux alentours des zones industrielles d’Abidjan (Yopougon et Port-Bouët), des habitats précaires avec leurs corolaires de maladies (paludisme (68,4%), fièvre typhoïde (12,2%), etc.) et les mauvaises conditions de vie (53,4%). Au regard de ce qui précède, il serait recommandable aux industriels de mettre l’accent sur l’abattement des paramètres en deçà des normes. Les structures de contrôle étatique devraient assurer leur rôle régalien au sein des zones industrielles. © 2013 International Formulae Group. All rights reserved.Mots clés: Entreprises industrielles, Abidjan, paramètres physico-chimiques, Environnement, Impacts, pollution

Cooperative hybrid wireless-powerline channel transmission for peer-to-peer energy trading and sharing system

The Peer-to-Peer (P2P) energy trading and sharing (ETS) network derives from the conventional smart-grid systems. The smart-grids operate smart meters that may be equipped with both wireless and powerline communication standards. In this study, we extend this communication strategy to a hybrid wireless-powerline communication scheme operating in cooperation and involves transmitting the same information over these two channel infrastructure and combining the received signals using maximal ratio combining (MRC) at the receiver. To maximize the received signal strengths with improved bit error ratio (BER) at the receiver side, we form the characteristic channels into a matrix and use singular value decomposition (SVD) to process the signals. Compared to either zero-forcing (ZF) or minimum mean square error (MMSE) detection scheme, the proposed SVD processing achieves 5dB and 7dB better than ZF and MMSE respectively at 10-5BER performance when operated with 10-2impulsive noise probability

Optimization of Impulsive Noise Mitigation Scheme for PAPR Reduced OFDM Signals Over Powerline Channels

The IEEE 1901 powerline standard can be deployed using orthogonal frequency division multiplexing (OFDM) since it is robust over impulsive channels. However, the powerline channel picks up impulsive interference that the conventional OFDM driver cannot combat. Since the probability density function (PDF) of OFDM amplitudes follow the Rayleigh distribution, it becomes difficult to correctly predict the existence of impulsive noise (IN) in powerline systems. In this study, we use companding transforms to convert the PDF of the conventional OFDM system to a uniform distribution which avails the identification and mitigation of IN. Results show significant improvement in the output signal-to-noise ratio (SNR) when nonlinear optimization search is applied. We also show that the conventional PDF leads to false IN detection which diminishes the output SNR when nonlinear memoryless mitigation scheme such as clipping or blanking is applied. Thus, companding OFDM signals before transmission helps to correctly predict the optimal blanking or clipping threshold which in turn improves the output SNR performance