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The performance of a joint in airport rigid pavements can be evaluated using load transfer efficiency (LTE). Various existing methods to calculate LTE using different parameters were reviewed in this paper, illustrating how the performance of a joint that performs well is underestimated. To address this concern, a new parameter obtained from the deflection time history output of HWD (Heavy Weight Deflectometer) is being proposed to calculate LTE. Field measurements and FEM (Finite Element Method) modeling were employed to validate the proposed calculation in comparison with the conventional calculations of LTE. Based on the statistical analysis, the proposed method shows low variance and error compared to the conventional calculation of LTE in airport pavements. Moreover, core samples were collected along the tested joints to verify if the calculated values manifest the internal condition of the joints. The calculated results from the proposed LTE show a good agreement not only with the surface condition of the joints, but also with the collected core samples.

Block pavements require efficient distress detection and segmentation methods for quality control and pavement management systems. This research proposes TransUNet, a hybrid model for block and distress segmentation, combining convolutional neural networks (CNNs) and Vision transformers. The model adopts transfer learning to achieve accurate block segmentation, pre-training the model on a large wall image dataset and then fine-tuning it on a smaller set of block pavement images. This approach yields promising results with 77% intersection over union (IoU), 96.8% precision, 99.5% recall, and 98.1% F1-score, surpassing conventional CNN-based models, UNet and UNet +  + . The use of transfer learning not only enhances accuracy but also significantly reduces training time and computational resources, as it eliminates the need for a large dataset. For the block distress segmentation model, the proposed hybrid TransUNet model obtained a mIoU of 71.3% outperforming CNN-based models. The CNN models often struggle to handle the diverse distress types commonly found in block pavements, resulting in sub-optimal distress segmentation outcomes. By automating block and distress segmentation, the proposed models contribute to efficient maintenance planning and the development of sustainable infrastructure.

Intramolecular cyclization of 1,1‐diisopropyl‐ or diphenyl‐bis(phenylethynyl)‐silanes (2aand 2b) followed by bromination or trimethylsilylation were carried out to yield 1,1‐diisopropyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐dibromo‐siloles (3aand 3b) and 1,1‐diisoproyl‐ or ‐diphenyl‐3,4‐diphenyl‐2,5‐bis(trimethylsilyl)‐siloles (4aand 4b), respectively. The structures of 3a,band 4a,bwere confirmed using 1H, 13C, and 29Si NMR as well as FTIR spectroscopy. The absorption bands of the siloles 3a,band 4a,bin THF were measured at 303–325 nm with the molar absorptivities of 1.85 × 103~ 2.18 × 103cm−1·M−1. The excitation bands were measured at 347–376 nm and the emission peaks were measured at 409–445 nm. Cyclic voltammograms of 3aand 3bindicated oxidation peaks at 0.90 and 0.80 V and reduction peaks at −1.20 and −1.20 V, respectively. The cyclic voltammograms of 4aand 4bindicated two oxidation peaks between −0.05 and −0.95 V and two reduction peaks between −0.10 and −0.93 V, respectively. Compound 4aexhibits a better long cycle performance by almost 1000 cycles as compared that of 3aand 4b. The rate performance test of the anodes Li‐3aand Li‐4aexhibited better performance properties at various C rate than Li‐4b. According to discharge–charge curves, 4ashows one plateau at approximately 0.58 V of the first discharge curve and the initial discharge specific capacity of 972 mAh/g. The electrochemical impedance spectroscopy of 4aindicates low charge transfer resistance, good conductivity of the electrolyte, and fast chemical adsorption/desorption rate of electrolyte ions on electrode surface, due to the electronic structure of 4a. 1,1‐Diisopropyl‐ or ‐Diphenyl‐2,5‐dibromo‐ or ‐bis(trimethylsilyl)‐3,4‐diphneyl‐siloles and Discharge and charge curves

The type of payment is one of the important factors that has an effect on the health of employees, as a basic working condition. In the conventional research field of occupational safety and health, only the physical, chemical, biological, and ergonomic factors are treated as the main hazardous factors. Managerial factors and basic working conditions such as working hours and the type of payment are neglected. This paper aimed to investigate the association of the type of payment and the exposure to the various hazardous factors as an heuristic study.

Due to the growing the standard of living, bicycle interest has increased which concerns a negative effect in transportation. Although, bicycle road construction is increasing continuously, distress problem is occurred by empirical design which is conventionally used. To determine the optimum joint spacing, thin porous concrete pavement was constructed and measured with vibrating wire strain gauges. Joint spacing is varied in 1.5m, 3.0m, 6.0m intervals, with slab thickness 7cm. Early age behavior of thin porous concrete pavement is measured. As expected, more restraint occurred at the longer slabs.

Because of its superior ability to bond to substrate materials and its good resistance to freezing and thawing cycles, polymer concrete has been widely used for repairing airfield pavements. However, polymer concretes used in repairing airport pavements in South Korea have not lasted as long as originally predicted; this premature failure may be attributable to the incompatibility of the coefficient of thermal expansion (CTE) between the polymer concrete and the substrate concrete material. To lower the CTE of the polymer concrete, the amount of polymer must be decreased and the amount of coarse aggregates increased. To determine the optimum amounts of polymer and coarse aggregates, a new concept of film thickness is proposed. In this research, the laboratory evaluation was performed on the mixtures of polymer concrete to measure compressive strength and CTE. On the basis of these test results, it was discovered that a larger amount of coarse aggregates lowered the CTE value and increased the film thickness; these changes resulted in a higher compressive strength than that of a typical polymer concrete with fine aggregates. As expected, the CTE of the polymer concrete decreased as the amount of polymer decreased. On the basis of limited laboratory test results, a film thickness of 33.5 μm is recommended to satisfy the minimum requirement of compressive strength (21 MPa) for repair material in South Korea. This minimum film thickness can be achieved with a mix of 8.2% polymer and 91.8% sand. However, if coarse aggregates are substituted for 40% of the sand, the same film thickness can be maintained if the amount of polymer is reduced to 6.35%.

Because of its superior ability to bond to substrate materials and its good resistance to freezing and thawing cycles, polymer concrete has been widely used for repairing airfield pavements. However, polymer concretes used in repairing airport pavements in South Korea have not lasted as long as originally predicted; this premature failure may be attributable to the incompatibility of the coefficient of thermal expansion (CTE) between the polymer concrete and the substrate concrete material. To lower the CTE of the polymer concrete, the amount of polymer must be decreased and the amount of coarse aggregates increased. To determine the optimum amounts of polymer and coarse aggregates, a new concept of film thickness is proposed. In this research, the laboratory evaluation was performed on the mixtures of polymer concrete to measure compressive strength and CTE. On the basis of these test results, it was discovered that a larger amount of coarse aggregates lowered the CTE value and increased the film thickness; these changes resulted in a higher compressive strength than that of a typical polymer concrete with fine aggregates. As expected, the CTE of the polymer concrete decreased as the amount of polymer decreased. On the basis of limited laboratory test results, a film thickness of 33.5 Μm is recommended to satisfy the minimum requirement of compressive strength (21 MPa) for repair material in South Korea. This minimum film thickness can be achieved with a mix of 8.2% polymer and 91.8% sand. However, if coarse aggregates are substituted for 40% of the sand, the same film thickness can be maintained if the amount of polymer is reduced to 6.35%.

An aerobic digestion coupled with membrane filtration (ADMF) system was investigated to determine the influence of various operating conditions to the efficiency of sludge thickening. Three different parameters were studied: the effect of hydraulic retention time (HRT), aeration and addition of coagulant. The effect of varying HRT was noticeable with the decrease in viscosity with increasing HRT. Transmembrane pressure, which indicates the extent of membrane fouling, increased with the decrease in HRT. Effect of aeration on the rate of increase in mixed liquor suspended solid concentration was observed to be insignificant, indicating that the aeration rate affected the filtration performance rather than the sludge reduction efficiency. Study on the effect of coagulant was evaluated by comparing two kinds of coagulants, organic and inorganic, at different concentrations. Dead-end filtration experiment and determination of critical flux were conducted to investigate the permeate performance according to coagulant addition. Higher value of critical flux was obtained with the addition of inorganic coagulant, while the total resistance was decreased with increasing coagulant concentration. Results show that while the addition of inorganic coagulant enhanced the ADMF system by improving membrane permeability, it is recommended that the system be operated at high HRT and aeration rate.

An aerobic digestion coupled with membrane filtration (ADMF) system was investigated to determine the influence of various operating conditions to the efficiency of sludge thickening. Three different parameters were studied: the effect of hydraulic retention time (HRT), aeration and addition of coagulant. The effect of varying HRT was noticeable with the decrease in viscosity with increasing HRT. Transmembrane pressure, which indicates the extent of membrane fouling, increased with the decrease in HRT. Effect of aeration on the rate of increase in mixed liquor suspended solid concentration was observed to be insignificant, indicating that the aeration rate affected the filtration performance rather than the sludge reduction efficiency. Study on the effect of coagulant was evaluated by comparing two kinds of coagulants, organic and inorganic, at different concentrations. Dead-end filtration experiment and determination of critical flux were conducted to investigate the permeate performance according to coagulant addition. Higher value of critical flux was obtained with the addition of inorganic coagulant, while the total resistance was decreased with increasing coagulant concentration. Results show that while the addition of inorganic coagulant enhanced the ADMF system by improving membrane permeability, it is recommended that the system be operated at high HRT and aeration rate.

The study investigated the effect of organic loading on nutrient and organic matter removal in a lab-scale membrane bioreactor (MBR). The effect of powdered activated carbon (PAC) addition on the performance of MBR was also considered. The results showed that the organic loading changes greatly affected the removal of total phosphorus (TP). At the end of the step increase in chemical oxygen demand (COD) from 300 mg/L to 2400 mg/L, the TP removal was completely removed. The COD and total nitrogen (TN) removals were 90% and 80%, respectively. When the COD was reduced to 1200 mg COD/L and 600 mg COD/L, the TP removal was 10% for MBR without PAC and 19% for MBR with PAC. The addition of PAC had no effect on nutrient and organic matter removal of the MBR. It only reduced membrane fouling; hence extending the operation time for MBR before membrane cleaning. The study demonstrated that MBR could maintain high effluent quality at high organic loading changes. Under low organic loading changes, TP removal deteriorated more than did the COD and TN removals. It was suggested that the dynamics of organic loading also be considered for the MBR process to sustain high effluent quality especially during start-up.

The study investigated the effect of organic loading on nutrient and organic matter removal in a lab-scale membrane bioreactor (MBR). The effect of powdered activated carbon (PAC) addition on the performance of MBR was also considered. The results showed that the organic loading changes greatly affected the removal of total phosphorus (TP). At the end of the step increase in chemical oxygen demand (COD) from 300 mg/L to 2400 mg/L, the TP removal was completely removed. The COD and total nitrogen (TN) removals were 90% and 80%, respectively. When the COD was reduced to 1200 mg COD/L and 600 mg COD/L, the TP removal was 10% for MBR without PAC and 19% for MBR with PAC. The addition of PAC had no effect on nutrient and organic matter removal of the MBR. It only reduced membrane fouling; hence extending the operation time for MBR before membrane cleaning. The study demonstrated that MBR could maintain high effluent quality at high organic loading changes. Under low organic loading changes, TP removal deteriorated more than did the COD and TN removals. It was suggested that the dynamics of organic loading also be considered for the MBR process to sustain high effluent quality especially during start-up.

The performance of a lab-scale membrane bioreactor (MBR) was evaluated based on its microbial community as well as the mechanism of membrane fouling. The growth of unwanted microorganisms in the system was observed, affecting effluent water quality. The MBR achieved a total-nitrogen removal of 56%. Nitrification and denitrification processes were most likely affected by the presence of Thiosphaera pantotropha, a bacterium capable of nitrification and denitrification processes. Phosphorus removal of 51% was attained, which is comparably lower than other existing systems. Furthermore, a chemical oxygen demand removal of 98% indicated the presence of active microbial community. However, this does not guarantee the existence of the target microorganisms. It was found that the increase in transmembrane pressure was caused by sludge-cake resistance rather than membrane-pore fouling. This conclusion was made by analyzing particle-size distribution and quantifying extracellular polymeric substances particularly soluble microbial products. The fouling mechanism was investigated by analyzing the membrane surface image generated by confocal laser scanning microscopy and scanning electron microscopy, and confirmed that MBR sludge were easily removed by physical cleaning. Hindering the growth of undesirable organism and controlling the concentration of soluble microbial product, which causes severe fouling, could lead to an efficient performance of MBR system.

The performance of a lab-scale membrane bioreactor (MBR) was evaluated based on its microbial community as well as the mechanism of membrane fouling. The growth of unwanted microorganisms in the system was observed, affecting effluent water quality. The MBR achieved a total-nitrogen removal of 56%. Nitrification and denitrification processes were most likely affected by the presence of Thiosphaera pantotropha, a bacterium capable of nitrification and denitrification processes. Phosphorus removal of 51% was attained, which is comparably lower than other existing systems. Furthermore, a chemical oxygen demand removal of 98% indicated the presence of active microbial community. However, this does not guarantee the existence of the target microorganisms. It was found that the increase in transmembrane pressure was caused by sludge-cake resistance rather than membrane-pore fouling. This conclusion was made by analyzing particle-size distribution and quantifying extracellular polymeric substances particularly soluble microbial products. The fouling mechanism was investigated by analyzing the membrane surface image generated by confocal laser scanning microscopy and scanning electron microscopy, and confirmed that MBR sludge were easily removed by physical cleaning. Hindering the growth of undesirable organism and controlling the concentration of soluble microbial product, which causes severe fouling, could lead to an efficient performance of MBR system.

The effect of impurity on the grain-boundary conduction in Sr- and Mg-doped lanthanum gallate (, LSGM) was studied. The grain-boundary conduction of LSGM was slightly affected, even by the addition of 500-2000 ppm , while the apparent grain-boundary resistivity was increased up to times in gadolinia-doped ceria by the doping of 500-2000 ppm . The high tolerance of the grain-boundary conduction against siliceous impurity in the LSGM specimen was explained by the gathering of the acidic siliceous phase near the basic SrO component.

This study examined the effect of adding SrO on the grain-boundary conduction of (gadolinia-doped ceria) containing . The apparent grain-boundary resistivity at decreased drastically from upon doping with SrO, while the grain-interior resistivity increased gradually from as the SrO concentration was increased up to . Therefore, doping with SrO resulted in the minimum total resistivity. The electron probe X-ray microanalysis and the analysis of the lattice parameters suggest that the 140-500-fold enhancement in the grain-boundary conduction is attributed to the scavenging of the highly resistive siliceous phase by the SrO-containing phase.

CZT detector is one of the most promising radiation detectors for hard X-ray and γ-ray measurement. The energy spectrum of CZT detector has to be simulated to optimize the detector design. A CZT detector was fabricated with dimensions of 5 × 5 × 2 mm3. A Peltier cooler with a size of 40 × 40 mm2was installed below the fabricated CZT detector to reduce the operation temperature of the detector. Energy spectra of were measured with 59.5 keV γ-ray from 241Am. A Monte Carlo code was developed to simulate the CZT energy spectrum, which was measured with a planar-type CZT detector, and the result was compared with the measured one. The simulation was extended to the CZT detector with strip electrodes.

CZT is one of the most promising materials for X-ray and γ-ray radiation detectors operated at room temperature. We have studied the fabrication process of the CZT planar-type detector, which includes the physical and chemical surface treatment, the fabrication of metal contact, and the surface passivation. CZT planar-type detectors with various metal-semiconductor contacts were made. The dark current and the γ-rays from 241Am were measured with each detector, and they were compared. From the above studies, the effective fabrication method of CZT detector could be deduced. Our work could be helpful to fabricate the high resolution CZT detector, which could be used in various application areas such as nuclear medicine, radiation safety, X-ray and γ-ray astronomy and homeland security

This paper describes an approach to minimizing the amount of shrinkage cracking in a cement-treated base (CTB). CTB is a stiff base that features higher rutting resistance and reduced fatigue cracking because of its ability to distribute traffic loads. However, it has not been applied to asphalt pavement in South Korea because of the possibility of reflection cracks. The goal of this study was to develop a cement-treated base with a lower shrinkage and thereby prevent cracks. After factors contributing to dry shrinkage were identified and the composition and properties of each admixture were analyzed, laboratory and field tests were designed and performed. The preliminary test results suggested a mix design of 25% fly ash. The amount of cement was set at 7% for all mixes to satisfy the specification standard for allowed strength in South Korea. On the basis of the experiment results, and considering strength, shrinkage, and economic efficiency, two mix designs were selected: a mixture containing 25% fly ash and a mixture containing 25% fly ash with 10% expansive additive. The field tests focused on crack propagation suggested that the optimal mixing alternative of a cement-treated base was the mix design of 25% fly ash and 10% expansive additive.

This paper describes an approach to minimizing the amount of shrinkage cracking in a cement-treated base (CTB). CTB is a stiff base that features higher rutting resistance and reduced fatigue cracking because of its ability to distribute traffic loads. However, it has not been applied to asphalt pavement in South Korea because of the possibility of reflection cracks. The goal of this study was to develop a cement-treated base with a lower shrinkage and thereby prevent cracks. After factors contributing to dry shrinkage were identified and the composition and properties of each admixture were analyzed, laboratory and field tests were designed and performed. The preliminary test results suggested a mix design of 25% fly ash. The amount of cement was set at 7% for all mixes to satisfy the specification standard for allowed strength in South Korea. On the basis of the experiment results, and considering strength, shrinkage, and economic efficiency, two mix designs were selected: a mixture containing 25% fly ash and a mixture containing 25% fly ash with 10% expansive additive. The field tests focused on crack propagation suggested that the optimal mixing alternative of a cement-treated base was the mix design of 25% fly ash and 10% expansive additive.

A case study of flexible overlay performance on an old rigid pavement is presented. This special study was devised in cooperation with the Pavement Section of the Design Division of the Texas Department of Transportation to take advantage of a unique opportunity to study overlay effectiveness. Condition survey, roughness measurements, and deflection basins were taken before and after the removal of an old flexible overlay and after the construction of a new asphalt overlay. Subsequent analysis of the data shows that although the overlay restores the ride quality of a rigid pavement and eliminates dynamic loading caused by swelling subgrades, it can only slow, not reverse, fatigue in the underlying pavement structure.

A case study of flexible overlay performance on an old rigid pavement is presented. This special study was devised in cooperation with the Pavement Section of the Design Division of the Texas Department of Transportation to take advantage of a unique opportunity to study overlay effectiveness. Condition survey, roughness measurements, and deflection basins were taken before and after the removal of an old flexible overlay and after the construction of a new asphalt overlay. Subsequent analysis of the data shows that although the overlay restores the ride quality of a rigid pavement and eliminates dynamic loading caused by swelling subgrades, it can only slow, not reverse, fatigue in the underlying pavement structure.

The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). An attempt was made to find a reasonable solution for pavements with SRG. As a way to solve the performance problem observed from the SRG pavement, a blended aggregates mixture was suggested. Laboratory and field tests were performed to check the feasibility of their application in pavements. From the laboratory test, a 50:50 blending ratio was suggested after considering the effect on tensile strength and thermal coefficient of expansion. Field test sections were also constructed to verify previous performance observations for the two aggregates and to provide performance data for new variables such as blended aggregates and special curing methods. Unexpectedly, the blended mixture did not improve the performance of SRG pavement; rather it experienced worse cracking than SRG alone. A controlled experiment with additional field test sections is needed to verify or disprove this finding. The only definitive finding was that selection of aggregate in the concrete pavement is a vital consideration for the design of the pavement. The CRCP8 analytical program reasonably predicted crack spacing for both SRG and LS pavements, predicting mean crack spacing of 0.99 m (3.25 ft) for SRG and 1.98 m (6.41 ft) for the limestone. These values are somewhat below the actual spacing observed at 100 days. Data collected after the first winter period will be required to calibrate the program.

Finite-element models have been applied extensively to the design and analysis of pavement structures. Three types of models have been used to study multilayered pavement structures: plane strain, axisymmetric, and three-dimensional (3-D). The applicability of each these three models and their disadvantages and advantages are discussed. Within the research community, an issue frequently raised about the application of the finite-element method (FEM) to pavement structures is the dependence of the solution on the simplifications that are introduced to reduce computational time and mesh configurations and element size, type, and aspect ratio. This issue is discussed extensively with the primary objective of comparing the solutions derived from FEM models with those from classic mechanistic models. The FEM solutions were derived with a commercial software package, ABAQUS, which is designed as a flexible tool for the implementation of FEM. The solution from the BISAR layered theory model for the traffic loading results was chosen for comparisons with the FEM solution. The 3-D and axisymmetric FEM models yielded results suitable for the traffic loading analysis.

The effect of coarse aggregate on pavement performance has been attributed to the volume of aggregate used in pavement construction. The different patterns of crack development for limestone (LS) and siliceous river gravel (SRG) are a typical example of aggregate-induced variable performance in continuously reinforced concrete pavement (CRCP). An attempt was made to find a reasonable solution for pavements with SRG. As a way to solve the performance problem observed from the SRG pavement, a blended aggregates mixture was suggested. Laboratory and field tests were performed to check the feasibility of their application in pavements. From the laboratory test, a 50:50 blending ratio was suggested after considering the effect on tensile strength and thermal coefficient of expansion. Field test sections were also constructed to verify previous performance observations for the two aggregates and to provide performance data for new variables such as blended aggregates and special curing methods. Unexpectedly, the blended mixture did not improve the performance of SRG pavement; rather it experienced worse cracking than SRG alone. A controlled experiment with additional field test sections is needed to verify or disprove this finding. The only definitive finding was that selection of aggregate in the concrete pavement is a vital consideration for the design of the pavement. The CRCP8 analytical program reasonably predicted crack spacing for both SRG and LS pavements, predicting mean crack spacing of 0.99 m (3.25 ft) for SRG and 1.98 m (6.41 ft) for the limestone. These values are somewhat below the actual spacing observed at 100 days. Data collected after the first winter period will be required to calibrate the program.

Finite-element models have been applied extensively to the design and analysis of pavement structures. Three types of models have been used to study multilayered pavement structures: plane strain, axisymmetric, and three-dimensional (3-D). The applicability of each these three models and their disadvantages and advantages are discussed. Within the research community, an issue frequently raised about the application of the finite-element method (FEM) to pavement structures is the dependence of the solution on the simplifications that are introduced to reduce computational time and mesh configurations and element size, type, and aspect ratio. This issue is discussed extensively with the primary objective of comparing the solutions derived from FEM models with those from classic mechanistic models. The FEM solutions were derived with a commercial software package, ABAQUS, which is designed as a flexible tool for the implementation of FEM. The solution from the BISAR layered theory model for the traffic loading results was chosen for comparisons with the FEM solution. The 3-D and axisymmetric FEM models yielded results suitable for the traffic loading analysis.

The effect of SiO2impurity on the grain-boundary conduction in Sr- and Mg-doped lanthanum gallate (La0.8Sr0.2Ga0.8Mg0.2O3−δ, LSGM) was studied. The grain-boundary conduction of LSGM was slightly affected, even by the addition of 500–2000 ppm SiO2, while the apparent grain-boundary resistivity was increased up to ∼780times in gadolinia-doped ceria by the doping of 500–2000 ppm SiO2. The high tolerance of the grain-boundary conduction against siliceous impurity in the LSGM specimen was explained by the gathering of the acidic siliceous phase near the basic SrO component.

This study examined the effect of adding SrO on the grain-boundary conduction of Ce0.9Gd0.1O1.95(gadolinia-doped ceria) containing 500ppmSiO2. The apparent grain-boundary resistivity at 300°Cdecreased drastically from 746.7to0.90–1.97kΩcmupon doping with ⩾1mol%SrO, while the grain-interior resistivity increased gradually from 3.1to11.6kΩcmas the SrO concentration was increased up to 5mol%. Therefore, doping with 1mol%SrO resulted in the minimum total resistivity. The electron probe X-ray microanalysis and the analysis of the lattice parameters suggest that the 140–500-fold enhancement in the grain-boundary conduction is attributed to the scavenging of the highly resistive siliceous phase by the SrO-containing phase.