Hydroxyapatite (HA) is widely explored as a biocompatible filler to enhance the mechanical and functional properties of glass ionomer cements (GICs). HA of particle sizes 15 µm and 30 µm were added as a fill...Hydroxyapatite (HA) is widely explored as a biocompatible filler to enhance the mechanical and functional properties of glass ionomer cements (GICs). HA of particle sizes 15 µm and 30 µm were added as a filler into a matrix, composed of calcium aluminosilicate GICs and Poly-acrylic acid (PAA) in varying ratios. The tested ratios were Glass:PAA = 2:1 and Glass:HA:PAA = 2:0.5:1 to improve the mechanical strength of a conventional GIC. Mechanical properties, including compressive, flexural, and diametral tensile strength were studied at different setting times. The compressive strength (CS) was improved with hydroxyapatite addition and prolonged setting time while diametral tensile strength (DTS) did not follow any specific trend. The flexural strength (FS) of the composite cement was increased with increasing setting time regardless of the particle size of hydroxyapatite. The FTIR spectra of hydroxyapatite of particle sizes 15 μm and 30 μm are similar but for HA-GIC composites, the FTIR spectra, the peak around 1460 cm−1 are due to C-H and the peak at 1553 cm−1 is due to calcium carboxylate with calcium in a bridging mode which would be an excellent material that chemically bonds to the tooth structure, making it effective for both restorative procedures and cavity fillings. Scanning electron microscopy (SEM) microstructural study revealed that the glass particles were wrenched out, which was a cohesive fracture. The X-ray diffraction (XRD) pattern showed that the hydroxyapatite has a crystalline single-phase, hexagonal structure. The sharp peaks between the 2-theta range of 30 - 40 degrees are the same as in enamel powder. The spectra indicate the pure set cement as amorphous since there is no prominent peak, but with the addition of hydroxyapatite filler, the peak in the 2-theta range of 20 - 35 degrees is ascribed to crystalline apatite structure. The results indicate that incorporating hydroxyapatite into GIC significantly enhances its mechanical properties and structural integrity, suggesting its potential as an improved material for dental and restorative applications.展开更多
Network lifetime is one of the important metrics that indicate the performance of a sensor network. Different techniques are used to elongate network lifetime. Among them, clustering is one of the popular techniques. ...Network lifetime is one of the important metrics that indicate the performance of a sensor network. Different techniques are used to elongate network lifetime. Among them, clustering is one of the popular techniques. LEACH (Low-Energy Adaptive Clustering Hierarchy) is one of the most widely cited clustering solutions due to its simplicity and effectiveness. LEACH has several parameters that can be tuned to get better performance. Percentage of cluster heads is one such important parameter which affects the network lifetime significantly. At present it is hard to find the optimum value for the percentage of cluster head parameter due to the absence of a complete mathematical model on LEACH. A complete mathematical model on LEACH can be used to tune other LEACH parameters in order to get better performance. In this paper, we formulate a new and complete mathematical model on LEACH. From this new mathematical model, we compute the value for the optimal percentage of cluster heads in order to increase the network lifetime. Simulation results verify both the correctness of our mathematical model and the effectiveness of computing the optimal percentage of cluster heads to increase the network lifetime.展开更多
Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group fr...Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group from Comilla region in Bangladesh. Three sets of samples were prepared for three different wt% (5%, 10% and 20%) of fiber contents. The mechanical (tensile strength, flexural stress, micro hardness, Leeb’s rebound hardness) and physical (bulk density and water absorption) properties were measured. The observed result reveals that the tensile strength (TS) and flexural stress (FS) were decreased with increasing fiber contents in the PF-ABS composites except 10% fiber content.展开更多
Stability is one of the major concerns in advancement of Wireless Sensor Networks (WSN). A number of applications of WSN require guaranteed sensing, coverage and connectivity throughout its operational period. Death o...Stability is one of the major concerns in advancement of Wireless Sensor Networks (WSN). A number of applications of WSN require guaranteed sensing, coverage and connectivity throughout its operational period. Death of the first node might cause instability in the network. Therefore, all of the sensor nodes in the network must be alive to achieve the goal during that period. One of the major obstacles to ensure these phenomena is unbalanced energy consumption rate. Different techniques have already been proposed to improve energy consumption rate such as clustering, efficient routing, and data aggregation. However, most of them do not consider the balanced energy consumption rate which is required to improve network stability. In this paper, we present a novel technique, Stable Sensor Network (SSN) to achieve balanced energy consumption rate using dynamic clustering to guarantee stability in WSN. Our technique is based on LEACH (Low-Energy Adaptive Clustering Hierarchy), which is one of the most widely deployed simple and effective clustering solutions for WSN. We present three heuristics to increase the time before the death of first sensor node in the network. We devise the algorithm of SSN based on those heuristics and also formulate its complete mathematical model. We verify the efficiency of SSN and correctness of the mathematical model by simulation results. Our simulation results show that SSN significantly improves network stability period compared to LEACH and its best variant.展开更多
Potatoes have to be stored after harvest for a shorter or longer period in order to maintain even supply to the market throughout the year for direct human consumption as well as for the processing industry. The prese...Potatoes have to be stored after harvest for a shorter or longer period in order to maintain even supply to the market throughout the year for direct human consumption as well as for the processing industry. The present study focused on the storage potentialities of six exotic varieties of potato viz., Diamant, Cardinal, Granola, Felsina, Provento and Asterix at farmers’ condition. The experiment was conducted during winter (December to March) for cultivation, and spring and summer (March to August) for storage at Domar Foundation Seed Potato Production Farm, BADC, Nilphamari, Bangladesh. Results revealed that there were significant variations in storage behavior among the varieties of potato tubers. Asterix showed minimum weight loss (7.10%) which was statistically identical with Cardinal (7.85%) while it was maximum in Felsina (18.83%) followed by Provento (13.41%) during four months storage conditions practicing by farmers (farmers’ conditions). In respect of rotting, significantly highest degree was found in Felsina (18.72%) followed by Provento (15.01%) and the lowest was in Asterix (2.02%) identically similar with Granola (2.22%). The highest percentage of water loss was found in Provento (27.01%) and the lowest was recorded in Asterix (17.03%). Dormancy period and sprouts per tuber were found highest in Asterix (70 days and 9.67) while the lowest dormancy was in Diamant (56 days) and the lowest sprouting was in Granola (2.50). Asterix was found to produce significantly highest amount of dry matter content (20.50%) along with higher amount of edible stored tubers (80.21%) compared to those of other varieties at the end of four months storage. Under the same condition, Diamant was the second highest producer of dry matter (20%) which was statistically similar with Asterix, and had good storage ability that retained 69.07% edible tubers, whereas Felsina contained the lowest amount of dry matter (16%) and showed poor storage ability retaining 55.85% edible tubers. Based on the results, Asterix possessed better keeping quality with long dormancy, minimum weight loss, higher tuber dry matter with edible tuber, excellent storage ability, low storage losses and rotting. However, the variety Asterix may be recommended for commercial storage under ordinary storage condition or farmers’ practice. Diamant ranked in second position considering the above circumstances, although showed better performances compared to the rest of the studied varieties.展开更多
The existence of various geo-location applications and their accuracy requirements enhance the necessities for suitable processing techniques to solve the indoor geo-location problems. Since, Impulse Radio Ultra-Wideb...The existence of various geo-location applications and their accuracy requirements enhance the necessities for suitable processing techniques to solve the indoor geo-location problems. Since, Impulse Radio Ultra-Wideband (IR-UWB) signals have very short duration pulses;they can provide very accurate ranging and geo-location capability in short range indoor radio propagation environments. Our research puts emphasis on indoor geo-location using UWB signaling considering both of non line-of-sight (NLOS) and LOS radio propagation environments. In this paper, we introduce and investigate a noble approach which makes a hybrid combination of Channel Impulse Response (CIR)-based finger-printing (FP) method with polygonal arrangement of reference nodes (or tags) and an iterative-TOA based real-time geo-location method using UWB signaling for wireless ad hoc networks. The proposed hybrid approach assures significant improvement in positioning accuracy compared to TOA only, FP only and conventional iterative-TOA geo-location methods by mitigating NLOS errors effectively in the indoor environment. Besides, this hybrid approach minimizes the calculation complexity of the FP method while maintaining improved geo-location accuracy in the dense multipath propagation environment.展开更多
Six modern varieties of potatoes (Diamant, Cardinal, Granola, Felsina, Provento and Asterix) were investigated for their growth parameters and yield to determine their suitability for production in Bangladesh. Results...Six modern varieties of potatoes (Diamant, Cardinal, Granola, Felsina, Provento and Asterix) were investigated for their growth parameters and yield to determine their suitability for production in Bangladesh. Results indicate significant variations among the varieties in the yield and morphological characteristics and no difference in the number of main stems per hill. Among the six studied varieties, Asterix produced the greatest yield (29.60 t/ha), the greatest number of tubers per hill (13 tubers/hill), the largest percentage (84%) of medium sized tubers (28 - 55 mm diameter), and the greatest plant height (61.33 cm). Diamant performed second after Asterix with a yield of 28.33 t/ha, and a plant height of 59.0 cm. Felsina produced the lowest yield (25.13 t/ha) and the lowest number of tubers per hill (8.67 tubers/hill). In a farmers’ perception study, where farmers scored the yield and resistance to diseases and insect damage of the six varieties, from 1 to 6 (6 being the highest and 1 being the lowest), Asterix was the most preferred variety by farmers with scores of 6, 5.67 and 5.83 for yield, disease resistance and insect resistance respectively. Provento was the least preferred by farmers with a score of overall performance of 4. The results of this study indicate that Asterix and Diamant have the potential to be grown successfully by the farmers in Bangladesh.展开更多
The composite materials are replacing the conventional materials, owing to their excellent properties. The developments of new materials are on the anvil and are thriving day by day. Natural fiber composites such as p...The composite materials are replacing the conventional materials, owing to their excellent properties. The developments of new materials are on the anvil and are thriving day by day. Natural fiber composites such as palm fiber (PF) polymer composites became more enchanting because of their high specific strength, low weight and biodegradability. Mixing of natural fiber like PF with acrylonitrile butadiene styrene (ABS) polymer is finding increased applications. In this work, PF reinforced ABS composites PF-ABS was fabricated by Injection Moulding Machine. The effect of UV-Visible radiation on PF-ABS composites was studied by means of ultraviolet-visible spectroscopy in the wavelength 200 - 1000 nm at room temperature. The present investigation shows that the addition of palm fiber modifies the absorption property of the materials. The absorption ability is maximal for 10% PF-ABS composites while minimal for 20% PF-ABS composites in the visible region of the spectrum. Optical constant like direct band gap energy, Urbach energy and Steepness parameter were determined using absorbance data. The values of direct energy band gap, Urbach energy as well as Steepness parameter were found to be in the range 2.6 - 3.9 eV, 0.40 - 0.85 eV and 0.03 - 0.06, respectively. It was observed that the value of direct band gap energy as well as Urbach energy is higher while the value of Steepness parameter is lower for PF-ABS composites with 10% palm fiber.展开更多
Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with n...Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with no implant residues in the surrounding tissues.In recent years,three classes of BMs have been extensively investigated,including magnesium(Mg)-based,iron(Fe)-based,and zinc(Zn)-based BMs.Among these three BMs,Mg-based materials have undergone the most clinical trials.However,Mg-based BMs generally exhibit faster degradation rates,which may not match the healing periods for bone tissue,whereas Fe-based BMs exhibit slower and less complete in vivo degradation.Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates,which fall between those of Mg-based BMs and Fe-based BMs,thus requiring extensive research to validate their suitability for biomedical applications.In the present study,recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs.The underlying roles of alloy composition,microstructure,and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.展开更多
文摘Hydroxyapatite (HA) is widely explored as a biocompatible filler to enhance the mechanical and functional properties of glass ionomer cements (GICs). HA of particle sizes 15 µm and 30 µm were added as a filler into a matrix, composed of calcium aluminosilicate GICs and Poly-acrylic acid (PAA) in varying ratios. The tested ratios were Glass:PAA = 2:1 and Glass:HA:PAA = 2:0.5:1 to improve the mechanical strength of a conventional GIC. Mechanical properties, including compressive, flexural, and diametral tensile strength were studied at different setting times. The compressive strength (CS) was improved with hydroxyapatite addition and prolonged setting time while diametral tensile strength (DTS) did not follow any specific trend. The flexural strength (FS) of the composite cement was increased with increasing setting time regardless of the particle size of hydroxyapatite. The FTIR spectra of hydroxyapatite of particle sizes 15 μm and 30 μm are similar but for HA-GIC composites, the FTIR spectra, the peak around 1460 cm−1 are due to C-H and the peak at 1553 cm−1 is due to calcium carboxylate with calcium in a bridging mode which would be an excellent material that chemically bonds to the tooth structure, making it effective for both restorative procedures and cavity fillings. Scanning electron microscopy (SEM) microstructural study revealed that the glass particles were wrenched out, which was a cohesive fracture. The X-ray diffraction (XRD) pattern showed that the hydroxyapatite has a crystalline single-phase, hexagonal structure. The sharp peaks between the 2-theta range of 30 - 40 degrees are the same as in enamel powder. The spectra indicate the pure set cement as amorphous since there is no prominent peak, but with the addition of hydroxyapatite filler, the peak in the 2-theta range of 20 - 35 degrees is ascribed to crystalline apatite structure. The results indicate that incorporating hydroxyapatite into GIC significantly enhances its mechanical properties and structural integrity, suggesting its potential as an improved material for dental and restorative applications.
文摘Network lifetime is one of the important metrics that indicate the performance of a sensor network. Different techniques are used to elongate network lifetime. Among them, clustering is one of the popular techniques. LEACH (Low-Energy Adaptive Clustering Hierarchy) is one of the most widely cited clustering solutions due to its simplicity and effectiveness. LEACH has several parameters that can be tuned to get better performance. Percentage of cluster heads is one such important parameter which affects the network lifetime significantly. At present it is hard to find the optimum value for the percentage of cluster head parameter due to the absence of a complete mathematical model on LEACH. A complete mathematical model on LEACH can be used to tune other LEACH parameters in order to get better performance. In this paper, we formulate a new and complete mathematical model on LEACH. From this new mathematical model, we compute the value for the optimal percentage of cluster heads in order to increase the network lifetime. Simulation results verify both the correctness of our mathematical model and the effectiveness of computing the optimal percentage of cluster heads to increase the network lifetime.
文摘Palm fiber (PF) reinforced acrylonitrile butadiene styrene (ABS) composite matrix was prepared by employing Injection Moulding Machine (IMM). Palm fiber was collected from ten different trees of different age group from Comilla region in Bangladesh. Three sets of samples were prepared for three different wt% (5%, 10% and 20%) of fiber contents. The mechanical (tensile strength, flexural stress, micro hardness, Leeb’s rebound hardness) and physical (bulk density and water absorption) properties were measured. The observed result reveals that the tensile strength (TS) and flexural stress (FS) were decreased with increasing fiber contents in the PF-ABS composites except 10% fiber content.
文摘Stability is one of the major concerns in advancement of Wireless Sensor Networks (WSN). A number of applications of WSN require guaranteed sensing, coverage and connectivity throughout its operational period. Death of the first node might cause instability in the network. Therefore, all of the sensor nodes in the network must be alive to achieve the goal during that period. One of the major obstacles to ensure these phenomena is unbalanced energy consumption rate. Different techniques have already been proposed to improve energy consumption rate such as clustering, efficient routing, and data aggregation. However, most of them do not consider the balanced energy consumption rate which is required to improve network stability. In this paper, we present a novel technique, Stable Sensor Network (SSN) to achieve balanced energy consumption rate using dynamic clustering to guarantee stability in WSN. Our technique is based on LEACH (Low-Energy Adaptive Clustering Hierarchy), which is one of the most widely deployed simple and effective clustering solutions for WSN. We present three heuristics to increase the time before the death of first sensor node in the network. We devise the algorithm of SSN based on those heuristics and also formulate its complete mathematical model. We verify the efficiency of SSN and correctness of the mathematical model by simulation results. Our simulation results show that SSN significantly improves network stability period compared to LEACH and its best variant.
文摘Potatoes have to be stored after harvest for a shorter or longer period in order to maintain even supply to the market throughout the year for direct human consumption as well as for the processing industry. The present study focused on the storage potentialities of six exotic varieties of potato viz., Diamant, Cardinal, Granola, Felsina, Provento and Asterix at farmers’ condition. The experiment was conducted during winter (December to March) for cultivation, and spring and summer (March to August) for storage at Domar Foundation Seed Potato Production Farm, BADC, Nilphamari, Bangladesh. Results revealed that there were significant variations in storage behavior among the varieties of potato tubers. Asterix showed minimum weight loss (7.10%) which was statistically identical with Cardinal (7.85%) while it was maximum in Felsina (18.83%) followed by Provento (13.41%) during four months storage conditions practicing by farmers (farmers’ conditions). In respect of rotting, significantly highest degree was found in Felsina (18.72%) followed by Provento (15.01%) and the lowest was in Asterix (2.02%) identically similar with Granola (2.22%). The highest percentage of water loss was found in Provento (27.01%) and the lowest was recorded in Asterix (17.03%). Dormancy period and sprouts per tuber were found highest in Asterix (70 days and 9.67) while the lowest dormancy was in Diamant (56 days) and the lowest sprouting was in Granola (2.50). Asterix was found to produce significantly highest amount of dry matter content (20.50%) along with higher amount of edible stored tubers (80.21%) compared to those of other varieties at the end of four months storage. Under the same condition, Diamant was the second highest producer of dry matter (20%) which was statistically similar with Asterix, and had good storage ability that retained 69.07% edible tubers, whereas Felsina contained the lowest amount of dry matter (16%) and showed poor storage ability retaining 55.85% edible tubers. Based on the results, Asterix possessed better keeping quality with long dormancy, minimum weight loss, higher tuber dry matter with edible tuber, excellent storage ability, low storage losses and rotting. However, the variety Asterix may be recommended for commercial storage under ordinary storage condition or farmers’ practice. Diamant ranked in second position considering the above circumstances, although showed better performances compared to the rest of the studied varieties.
文摘The existence of various geo-location applications and their accuracy requirements enhance the necessities for suitable processing techniques to solve the indoor geo-location problems. Since, Impulse Radio Ultra-Wideband (IR-UWB) signals have very short duration pulses;they can provide very accurate ranging and geo-location capability in short range indoor radio propagation environments. Our research puts emphasis on indoor geo-location using UWB signaling considering both of non line-of-sight (NLOS) and LOS radio propagation environments. In this paper, we introduce and investigate a noble approach which makes a hybrid combination of Channel Impulse Response (CIR)-based finger-printing (FP) method with polygonal arrangement of reference nodes (or tags) and an iterative-TOA based real-time geo-location method using UWB signaling for wireless ad hoc networks. The proposed hybrid approach assures significant improvement in positioning accuracy compared to TOA only, FP only and conventional iterative-TOA geo-location methods by mitigating NLOS errors effectively in the indoor environment. Besides, this hybrid approach minimizes the calculation complexity of the FP method while maintaining improved geo-location accuracy in the dense multipath propagation environment.
文摘Six modern varieties of potatoes (Diamant, Cardinal, Granola, Felsina, Provento and Asterix) were investigated for their growth parameters and yield to determine their suitability for production in Bangladesh. Results indicate significant variations among the varieties in the yield and morphological characteristics and no difference in the number of main stems per hill. Among the six studied varieties, Asterix produced the greatest yield (29.60 t/ha), the greatest number of tubers per hill (13 tubers/hill), the largest percentage (84%) of medium sized tubers (28 - 55 mm diameter), and the greatest plant height (61.33 cm). Diamant performed second after Asterix with a yield of 28.33 t/ha, and a plant height of 59.0 cm. Felsina produced the lowest yield (25.13 t/ha) and the lowest number of tubers per hill (8.67 tubers/hill). In a farmers’ perception study, where farmers scored the yield and resistance to diseases and insect damage of the six varieties, from 1 to 6 (6 being the highest and 1 being the lowest), Asterix was the most preferred variety by farmers with scores of 6, 5.67 and 5.83 for yield, disease resistance and insect resistance respectively. Provento was the least preferred by farmers with a score of overall performance of 4. The results of this study indicate that Asterix and Diamant have the potential to be grown successfully by the farmers in Bangladesh.
文摘The composite materials are replacing the conventional materials, owing to their excellent properties. The developments of new materials are on the anvil and are thriving day by day. Natural fiber composites such as palm fiber (PF) polymer composites became more enchanting because of their high specific strength, low weight and biodegradability. Mixing of natural fiber like PF with acrylonitrile butadiene styrene (ABS) polymer is finding increased applications. In this work, PF reinforced ABS composites PF-ABS was fabricated by Injection Moulding Machine. The effect of UV-Visible radiation on PF-ABS composites was studied by means of ultraviolet-visible spectroscopy in the wavelength 200 - 1000 nm at room temperature. The present investigation shows that the addition of palm fiber modifies the absorption property of the materials. The absorption ability is maximal for 10% PF-ABS composites while minimal for 20% PF-ABS composites in the visible region of the spectrum. Optical constant like direct band gap energy, Urbach energy and Steepness parameter were determined using absorbance data. The values of direct energy band gap, Urbach energy as well as Steepness parameter were found to be in the range 2.6 - 3.9 eV, 0.40 - 0.85 eV and 0.03 - 0.06, respectively. It was observed that the value of direct band gap energy as well as Urbach energy is higher while the value of Steepness parameter is lower for PF-ABS composites with 10% palm fiber.
基金support for this research by the Australian Research Council(ARC)through the discovery grant DP170102557 and ARC Future Fellowship(FT160100252)YL is also supported through an ARC Future Fellowship(FT160100252).
文摘Biodegradable metals(BMs)gradually degrade in vivo by releasing corrosion products once exposed to the physiological environment in the body.Complete dissolution of biodegradable implants assists tissue healing,with no implant residues in the surrounding tissues.In recent years,three classes of BMs have been extensively investigated,including magnesium(Mg)-based,iron(Fe)-based,and zinc(Zn)-based BMs.Among these three BMs,Mg-based materials have undergone the most clinical trials.However,Mg-based BMs generally exhibit faster degradation rates,which may not match the healing periods for bone tissue,whereas Fe-based BMs exhibit slower and less complete in vivo degradation.Zn-based BMs are now considered a new class of BMs due to their intermediate degradation rates,which fall between those of Mg-based BMs and Fe-based BMs,thus requiring extensive research to validate their suitability for biomedical applications.In the present study,recent research and development on Zn-based BMs are reviewed in conjunction with discussion of their advantages and limitations in relation to existing BMs.The underlying roles of alloy composition,microstructure,and processing technique on the mechanical and corrosion properties of Zn-based BMs are also discussed.
