Irregular repetition code hybrid ARQ in wireless system

Error control consists of error detection and error correction in the communication system. The purpose of this research work is to reduce error in the wireless communication system by using the advantages of both error correction techniques which are forward error correction (FEC) and automatic repeat request (ARQ). Thus, error can be corrected without retransmission and also via retransmission(s) when needed. Combination of FEC and ARQ is known as Hybrid ARQ. In this paper, Hybrid ARQ system is designed using three components which are the irregular repetition code (IRC) as a simple code, bit-interleaved coded modulation with iterative decoding (BICM-ID) as a simple Turbo processing and ARQ. The HARQ system is enhanced by the extended mapping (EM) adopted in the mapping system. The performance of the systems is evaluated in the additive white Gaussian noise (AWGN). The results show the Hybrid ARQ with extended mapping (Hybrid ARQ-EM) outperforms Hybrid ARQ with standard mapping (Hybrid ARQ-SM). Hybrid ARQ-EM achieves low bit error rate BER (10-5) at low signal-to-noise ratio SNR which only 3.03dB close to the theoretical limit. The proposed system Hybrid ARQ-EM achieves 52 percent gain enhancement of SNR gap from the theoretical limit compared to Hybrid ARQ-SM. Hybrid ARQ-EM gives better performance although in worse channel condition

Generation of Q-switched thulium-doped fiber laser (TDFL) using differentsaturable absorbers

A Q-switched Thulium-doped Fiber Laser (TDFL) operating at approximately 2 µm wavelength is successfully generated by using four different saturable absorbers (SAs) which are nitrogen-doped graphene in PVA (NG:PVA), nitrogen-doped graphene in PEO (NG:PEO), single-walled carbon nanotube in PVA (SWCNT:PVA), and high pressure carbon monoxide carbon nanotube in PVA (CNTHiPCO:PVA). The SAs integrated in the cavity were able to provide the real saturable absorption in modulating the intra-cavity losses. SWCNT gives the best results with the highest repetition rate and lowest pulse width of 57.45 kHz and 1.958 nJ correspondingly as compared to the other three SAs

Fractal Characteristic of Electrical Trees Grown in Silicone Rubber under Environmental Stress

One of the degradations of insulation is in the form of electrical treeing in which classified as a pre-breakdown phenomenon of electrical insulation. The electrical tree is commonly forming in the shape of tree-like or root-like which may have fractal structures. Due to this fractal structure, electrical treeing formation and patterns are analysed via fractal dimension and lacunarity to study the self-similarity patterns of electrical treeing. Many types of research have been conducted to study the fractal dimension and lacunarity of electrical treeing to fully understand the electrical tree mechanism and characteristics. However, fractal and lacunarity structures o

Comparison of habitual visual acuity and stereoacuity between children attending KEMAS and urban private preschools

The assessment of a preschooler’s visual status is important as it forms part of the measure to assess the child’s school readiness. However, not all children attending preschools have equal opportunity to undergo vision screening programmes. In this study, we measured presenting habitual near and distance visual acuity and stereoacuity in 6-year-old children (n=385). These parameters were measured in and compared between preschoolers attending urban, privately-run kindergartens and those attending KEMAS preschools, which were typically from suburban and rural areas with families of very low income. Seven percent of KEMAS preschoolers failed the distance visual acuity test while the failure rate for private preschoolers was 6.0%. For near visual acuity, a higher percentage of private preschoolers failed the test (8.7%) than KEMAS preschoolers (4.9%). A slightly higher percentage of private preschoolers had weak stereopsis (3.3%) compared to KEMAS preschoolers (2.5%). However, the differences found between the two preschooler groups were not statistically significant (all p>0.05). The proportion of children who failed each of the screening criteria for distance vision, near vision, and stereopsis was similar between KEMAS and private preschools. Therefore, an universally inclusive vision screening programme should be conducted for all preschool types to detect, diagnose, treat, and potentially prevent any visual impairment

Essential knowledge transfer process model to support disaster management

There is a lack of knowledge transfer modeling that focuses on the essence of the knowledge transfer process. This paper aims to identify the processes that are common and essential in the implementation of knowledge transfer from multiple senders to one receiver using the star topology as the architecture. This study extracts the actual processes involved during the flow of knowledge from the source to the receiver identified from the literature review and existing theories. The processes are identified as: acquire, convert, implement and store (ACIS). The model is illustrated in a case study of flood management in Malaysia. The utilization of the identified essential processes of knowledge transfer will provide stakeholders with a concrete way of transferring knowledge by standardizing the actual process of knowledge transfer. These processes may be applied in various domains that use the star topology as the communication architecture

Dynamic Mechanical Analysis of Bio-Based and Synthetic Petroleum Based Polymer Foams with Powder Type Organic Filler at Prolonged Ultra-Violet Exposure

Wood powder filler that have been added in the bio-based and epoxy polymer foams can be proved that it have ability to strengthen the structure of polymer foams. In this study, ‘Meranti’ type wood filler has been used as the filler. This study was developed to observe the pore size of each sample when expose to different hours of UV irradiation exposure using Optical Microscopy (OM). This study was also to compare the mechanical properties of every sample with different ratio filler of 0 wt%, 5 wt%, 10 wt%, 15wt% and 20 wt% at different hours of UV irradiation exposure which is 0 hour until 6,000 hours with increment of 2,000 hours. The testing was run by DMA Q800 TA machine. The samples that have 40 x 10 x 5 mm size were clamped in the machine to get the result of their mechanical properties. From the DMA testing, the results will show the value of tan delta, loss modulus and storage modulus. The value of tan delta shows that higher ratio filler will give the high value of tan delta. The epoxy polymer foams with powder filler have the highest value of tan delta compare to bio-based polymer foams. It proves that the higher filler ratio, the lower value of tan delta can be recorded.  The result of storage and loss modulus was found to increase as the more filler ratio filler in the polymer foams. The higher the loss modulus and storage modulus, the lower the temperature. Bio-based polymer foams with high powder filler ratio can dissipate more energy as energy are lost as heat during UV irradiation exposure

Effect of Lithium Chloride (Licl) Dopant on The Performance of Catalysts for the Oxidative Coupling of Methane

The present study reports effects of lithium chloride (LiCl) doping on MgO, La2O3, SnO2, CaO and ZnO catalysts. All the catalysts were prepared by the impregnation method. The catalysts were tested at reaction temperature of 775oC. The feed flow rate of methane, oxygen and nitrogen was carried out in the ratio of 3:1:2 giving a weight hourly space velocity (WHSV) of 0.375 g.s/cm3. La2O3 showed the highest C2+ selectivity among the undoped catalysts. All the catalysts were doped with LiCl to compare their methane conversion, selectivity and product yield. The 2.0 mol% LiCl doped into La2O3 was the best catalyst formulation having achieved 46.7% of C2+ selectivity with CH4 conversion of 29.0% and the increase in selectivity was attributed to the presence of chlorine. Hydrogen production was more pronounced for MgO based catalysts and believed to be generated by surfacecatalyzed reactions

Penggunaan Metode Semiempirik AM1 Untuk Pemilihan Monomer Fungsional Efektif Pada Prasintesis Polimer Tercetak Diazinon

Pemilihan monomer fungsional yang efektif untuk sintesis Molecular Imprinted Polymer (MIP)untuk diazinon dapat dilakukan dengan pendekatan kimia komputasi dengan menerapkan metode semiempirik AM1. Proses seleksi menggunakan parametermomen dipol, energi interaksi, dan ikatan hidrogen yang terbentuk. Energi interaksi yang optimum menunjukkan kompleks yang terbentuk stabildan mengindikasikan MIP akan dapat terbentuk baik.Semua perhitungan pada penelitian ini dilakukan dengan menggunakan software Hyperchem 7.5. Hasil penelitian menunjukkan monomer fungsional efektif untuk prasintesis polimer tercetak diazinon yaitu akrilamida, asam akrilat, asam metakrilat, hidroksi etil metakrilat, asam urokanat, asam itakonat, dan asam urokanat etil ester. Hasil ini secara teoritik dapat memberikan informasi mengenai monomer fungsional efektif yang dapat digunakan sebagai pertimbangan sintesis MIP untuk diazinon dengan selektivitas relatif baik

Analysis of AC-DC Converter Circuit Performance With Difference Piezoelectric Transducer Array Connection

This research presents a simulation analysis for the AC-DC converter circuit with a different configurations of the array connection of the piezoelectric sensor. The selection of AC-DC converter circuits is full wave bridge rectifier (FWBR), parallel SSHI (P-SSHI) and parallel voltage multiplier (PVM) with array configuration variation in series (S), parallel (P), series-parallel (SP) and parallel-series (PS). The system optimizes with different load configurations ranging from 10 kΩ to 1 MΩ. The best configuration of AC-DC converter with an appropriate array piezoelectric connection producing the optimum output of harvested power is presented. According to the simulation results, the harvested power produced by using P-SSHI converter connected with 3 parallel piezoelectric transducer array was 85.9% higher than for PVM and 15.88% higher than FWBR

Diuretic properties of Orthosiphon stamineus Benth.

Ethnopharmacological relevance: Orthosiphon stamineus has been used in traditional medicine for centuries especially to treat diseases of the urinary system. Aim of the study: To investigate the diuretic activity, to elucidate its possible mechanism and to evaluate the renal effects of Orthosiphon stamineus extract. Materials and methods: Water extracts were administered orally at doses of 5 and 10 mg/kg to Sprague-Dawley rats and the control groups were given commercial diuretic drugs either furosemide or hydrochlorthiazide at 10 mg/kg. Urine volume, urine pH, urine density and urine electrolytes were determined every hour for 4 h. Blood was assayed for glucose, albumin, blood urea nitrogen (BUN) and creatinine. Results: O. stamineus extract exhibited dose-dependent diuretic activity. However, excretion of Na+ and Cl- was not markedly elevated, but urinary excretion of K+ was significantly increased. O. stamineus extracts slightly increased the serum BUN, creatinine and blood glucose level. Although these levels were statistically significant when compared to control, these levels were still within normal range. Conclusions: O. stamineus exhibited diuretic activity, but was less potent than furosemide and hydrochlorothiazide. Care should be taken when consuming this herb as slight increase of kidney function enzymes was recorded