As the Editor-in-Chief of the Journal of Testing and Evaluation (JTE), I would like to sincerely thank the individuals listed here who provided reviews for the papers published in Volume 54 of JTE. Your time and efforts in providing constructive criticism for the authors help to maintain the high quality of our journal. Your generosity is greatly appreciated, and I do look forward to continuing your association with JTE in the future.
ABSTRACT The present study evaluates nano-encapsulated phase change materials (nano-PCMs [PCM-N]) incorporated into cementitious composites for thermally efficient building envelopes. Paraffin was encapsulated within a silica shell by a sol–gel route and incorporated into cementitious mixes at different dosages. Response surface methodology (RSM) based on a central composite design was used to optimize PCM dosage and curing time with thermal conductivity, latent heat capacity, and compressive strength as the response variables. Compared with the control mix, the PCM-N composite reduced thermal conductivity from 1.61 to 1.24 W/m·K, corresponding to an approximately 23 % reduction, whereas latent heat capacity reached 70.6 J/g at the highest dosage investigated. Thermal cycling results showed that the PCM-N system retained about 80–85 % of its initial thermal efficiency after 100 cycles, indicating better durability than the micro-PCM system. Under simulated solar loading, the PCM-N wall panel reduced the rear-face temperature from 42.6°C to 34.2°C, and building-scale simulation predicted an energy saving of 12.3 kWh with a carbon dioxide offset of 5.7 kg. The RSM analysis identified an optimal PCM-N dosage of 6.2 wt.% within the high-desirability region. These results demonstrate that silica-shelled PCM-Ns can improve the thermal regulation capability of cementitious composites, thereby maintaining acceptable mechanical performance for energy-efficient building envelope applications.
ABSTRACT This study systematically evaluated the mechanical response of Z-type and groove-type geomembranes under a combination of normal pressure (300–1,200 Pa) and slack allowance (1 %–3 %) using a self-developed geomembrane slack-allowance tensile testing device. The experiments show that the required tension of the Z-type geomembrane is linearly positively correlated with the normal pressure, and at 1,200 Pa, with a 3 % slack allowance, the required tension is 3.62 × 105 N/m, with the time-consumption curve showing nonlinear characteristics. Data integration reveals significant differences in the safety thresholds of the two methods. For geomembranes with a unidirectional Z-type slack allowance, when the slack allowance is 1 %, the maximum water head it can withstand is 71 m; when the slack allowance is 2 % and 3 %, the maximum water head is 53.5 and 51 m, respectively. For geomembranes with a unidirectional groove-type slack allowance, the maximum water heads they can withstand are 69 m when the slack allowances are 1 % and 2 % and 104 m when the slack is 3 %. The research results provide a quantitative basis for optimizing the slack allowance standards for HDPE geomembrane in hydraulic engineering.
ABSTRACT The performance of cement-stabilized macadam (CSM) is influenced by the duration of vibration compaction. However, the relationship between laboratory-prepared specimens under different compaction durations and the properties of field cores remains unclear. In this study, specimens were compacted using a vertical vibration compaction method for 90, 120, and 150 s (CSM-90, CSM-120, and CSM-150) to investigate the effect of compaction time on CSM performance. The unconfined compressive strength, indirect tensile strength, flexural tensile strength, fatigue, and shrinkage tests were conducted. Field core samples were used for comparison. The results showed the trend of mechanical and fatigue properties: CSM-120 > CSM-150 > field cores > CSM-90. The strength of CSM increased gradually, and the mixture became denser as the vibration compaction time increased. Compared with CSM-90, the compressive strength increase was the most obvious. CSM-120 and CSM-150 increased 34.71–48.43 % and 25.20–40.71 %. However, the long-time compaction resulted in aggregate breakage and large gradation variation, and the mechanical properties of CSM-150 decreased slightly. Compared with CSM-90, the drying shrinkage strains of CSM-120 and CSM-150 decreased by 29.21 % and 26.20 %, respectively. The drying shrinkage capacity of CSM increased with increasing vibration compaction time. However, the effect of compaction time on temperature shrinkage properties was insignificant. In conclusion, the performance of CSM could be improved by appropriately increasing the vibration compaction time, and the recommended compaction time was in the range of 90–120 s. This study could offer some advice for the practical application of CSM.
ABSTRACT This study explores the use of spark erosion machining for the manufacturing of circular profiles in ceramic composites composed of silicon nitride and titanium nitride (Si3N4–TiN). To address measuring criteria such as material removal rate, electrode wear rate, surface roughness, radial over cut, and geometric tolerances, four crucial machining factors have been taken into account: current, spark-on time, spark-off time, and dielectric pressure. Employing multi-criteria methods for making decisions such as technique for order preference by similarity to ideal solution (TOPSIS) and grey relational analysis (GRA), the optimal combination of machining configurations can be identified to optimize the efficiency of all replies. In conjunction with GRA, the teaching–learning-based optimization (TLBO) method—a metaheuristic or algorithm inspired by nature—determines the global ideal parameters. The magnitude of responses such as geometric tolerances, pulse-on time, and material removal rate is significantly affected by dielectric pressure, pulse-on time, and current. Two of the most crucial factors are the current and the pulse-on time, according to most respondents. The GRA and TOPSIS methodologies determined that a current of 3 A, a pulse-on duration of 5 μs, a pulse-off time of 10 μs, and a dielectric pressure of 15 kg/cm2 would get the best responses for Electrical Discharge Machining (EDMed). The best combination of process variables obtained from TLBO optimization is a current of 2.88 A, a pulse-on duration of 2.78 μs, a pulse-off time of 4 μs, and a dielectric pressure of 8.56 kg/cm2.
