Optimization of the Physical and Mechanical Properties of Grouting Material for Non-Soil-Squeezing PHC Pipe Pile

The physical and mechanical properties of grouting materials greatly affect the friction resistance and the bearing performance of a non-soil-squeezing PHC pipe pile. Orthogonal tests for four factors at five levels were carried out to optimize the proportion of the water–cement mixture by using Portland cement as a raw material and a water-reducing agent, expansion agent and early-strength agent as additives. The following conclusions were obtained: (1) Both the water–cement ratio and the dosage of water-reducing agent are positively correlated with the fluidity of the water–cement mixture and have the greatest influence on the fluidity, followed by the expansion agent and early-strength agent. The saturation point of the water-reducing agent is 1.5%. (2) The strength of the grouting body decreases linearly with the increase of the water–cement ratio, and the dosage of the water-reducing agent has no obvious effect on the strength. As the dosage of expansion agent increases, the strength of the grouting body decreases rapidly. The expansion agent mainly plays a key role in the middle and late stages of the hardening process of the slurry. Early-strength agents have a greater impact on the early strength, but less on the later strength. When the slurry is solidified for 3 h, the early-strength agent has the greatest impact on the strength with an optimal dosage of 5%. (3) The volume of the grouting body has an inverse relationship with the water–cement ratio, and the optimal amount of expansion agent is 12%. The incorporation of an expansion agent makes the volume increase of the grouting body exceed the volume shrinkage ratio caused by the hardening of the grouting body with a curing time of more than 3 days, ensuring a slight increase in the volume of the grouting body. After 3 days, even though the effect of the expansion agent is gradually weakened, it can still ensure that the volume of the grouting body does not shrink. With the increase of the amount of water-reducing agent, the volume of the grouting body gradually decreases. When the amount of water-reducing agent exceeds 1.5%, the volume of the grouting body no longer decreases. (4) The early-strength agent has almost no effect on the volume of the grouting body. When the curing time is 3 h, the water–cement ratio has the greatest influence on the volume of the grouting body, followed by the water-reducing agent, and, finally, the expansion agent. After 3 h, the water–cement ratio still has the greatest influence, and the influence of the expansion agent gradually exceeds that of the water-reducing agent. The water-reducing agent mainly affects the volume of the grouting body in the water separation stage, and the expansion agent mainly plays a role in the middle and late stages of the slurry solidification. After optimized ratio analysis, the fluidity of the water–cement mixture can be improved, the volume shrinkage ratio rate can be lowered and the early strength can be increased.

Research on the similarity of vibration characteristics of naval gun bracket based on similarity theory

The similar scale model experiment can provide some reference for the research and development of naval gun weapons. This paper takes the naval gun bracket as an example to explain. Based on the dimensional analysis, equation analysis and finite element method, the modal parameter similarity relationship between the original model for bracket and the shrinkage ratio model is established. The results show that the error of predicting the natural frequency of the original model based on similarity relation is less than 2% comparing with the results of finite element numerical simulation, and the error is less than 10% comparing with the experimental results, and the mode of shrinkage model is close to that of the original model. It is proved that the theoretical method in this paper is feasible and practical in engineering. Therefore, the vibration characteristics of the original model can be estimated by analyzing the vibration characteristics of the carrier shrinkage ratio model, which provides a reference for ship gun designers.

Effect of microwave, infrared, and convection hot-air on drying kinetics and quality properties of okra pods

Okra pods were dried using the following drying regimes; microwave (MWD), infrared (IRD) and convective hot-air drying (CHD). The objective of this investigate was to report the influences of drying methods on okra quality under different drying conditions. Data analysis showed that rehydration ratio and colour change increased with increase in drying air temperature and air velocity while specific energy consumption and shrinkage ratio decreased with increase in drying air temperature under (CHD). The rehydration ratio and colour of dried okra increased with increase in both infrared intensity but it also increased with a decrease in air velocity under (IRD). In the MWD method, drying time, specific energy consumption and shrinkage ratio decreased with increases in microwave power while the rehydration ratio and colour increased. Optimum drying period, specific energy consumption, colour, shrinkage and rehydration ratio were obtained for microwave drying. The model of Midilli et al. is the greatest for describing the drying curves of okra under all the drying processing conditions.

Study of the Impact of Protective Process Agents with Carbon Nanopowder Additives on Chip Forming Processes

The present study describes the impact of various protective process agents on chip forming processes. The research was conducted on NiCr20TiAl and 34NiCrMoV14-5 nickel-chromium alloys. New lubricant-cooling process agents with carbon nanopowder additives are studied. The optimal composition of the nanopowder additive and its effect during alloy cutting is examined. Experiments reveal the dependence of shrinkage ratio on cutting speed and various protective process agents. The values of H50 microhardness are also defined when cutting these alloys using protective process agents. Experimental studies found the positive effect of developed agents with nanopowder additives on the processes of NiCr20TiAl and 34NiCrMoV14-5 alloys chip formation.

PRA-PERLAKUAN BLANSING PADA PENGERINGAN TIPE BEKU (FREEZE DRYING) UNTUK MEMPERTAHANKAN KUALITAS PETAI (Parkia speciosa)

Petai (Parkia speciosa) merupakan salah satu jenis makanan yang memiliki ciri khas rasa yang unik serta nutrisi yang melimpah. Karakteristik tersebut membuat petai berpotensi untuk diolah menjadi sayuran eksotis dengan sasaran pasar nasional maupun internasional. Meskipun begitu, seperti halnya sayuran lain, kualitas petai sangat dipengaruhi oleh kondisi lingkungan. Salah satu solusi untuk penyimpanan petai adalah dengan proses pengeringan. Penelitian ini bertujuan untuk mengetahui pengaruh pra-perlakuan blansing terhadap kualitas fisik petai hasil pengeringan tipe beku (freeze-drying). Dua variasi jenis blansing, yaitu blansing dengan air panas (HWB) dan blansing dengan uap panas (SB) dilakukan sebelum proses pengeringan. Selain itu, pengeringan tipe cabinet juga dilakukan sebagai pembandingan. Kualitas yang diukur pada penelitian ini meliputi karakteristik pengeringan, kadar air, susut bobot, shrinkage ratio, kekerasan bahan, warna, dan kandungan klorofil. Pengering beku yang digunakan pada penelitian ini ialah pengering hasil rancangan sendiri yang berdimensi total 0,5 x 0,7 x 1,0 m. Hasil penelitian menunjukkan bahwa karakteristik penurunan kadar air pada proses pengeringan beku untuk petai secara baik dideskripsikan dengan model kinetika orde satu (R2 > 0,95; RMSE < 0,1). Kadar air akhir terendah didapatkan dari pengeringan beku, dengan rentang kadar air 2 – 3 % w.b. Pengeringan beku dapat mengurangi resiko discoloration pada petai, dibandingkan dengan pengering tipe cabinet. Pra-perlakuan blansing terbukti dapat membantu meningkatkan laju pengeringan sehingga pengeringan berlangsung lebih cepat, dan kandungan klorofil didalam petai dapat terjaga lebih baik.

Molecular dynamics study of alloying process of Cu–Au nanoparticles with different heating rates

In this paper, molecular dynamics (MD) simulation is utilized for the investigation of impact of heating rates on Au and Cu nanoparticles alloying process. Aggregation of contacted nanoparticles experiences three stages due to the contacting, while the alloying process can be distinguished into five regimes because of the contacting and melting. Different heating rates result in different contact temperatures. The decrease of the potential energy can be observed when the temperature reaches the melting temperature. When the temperature reaches the melting point, shrinkage ratio and relative gyration radius have drastic changes during the alloying process. It is shown that heating rates have an apparent effect on the shrinkage ratio and the relative gyration radius during the fusing process, and the shrinkage ratio and the relative gyration radius of Au and Cu alloying systems with lower heating rates have relative larger increasing ratio and decreasing ratio, respectively.

Effects of pretreatments on drying of Turkey berry in fluidized bed dryer

The influence of pre-treatment methods like physical, chemical, combined physical, and hybrid treatments on the Turkey berry fruits to enhance the water diffusion during drying was assessed due to the removal of a waxy layer on the peel. Pre-treated and untreated samples were dried at 70?C and 4 m/s of air flow in a fluidized bed dryer. Fruits pre-treated with combined abrasion and blanching have the lowest drying time, and favorable Vitamin-C content retention of 36%. The highest drying rate of 0.396 kg water/kg db min?1, maximum effective moisture diffusivity of 6.002 x 10-10 m2/s, and volumetric shrinkage ratio of 0.68 were obtained for fruits which undergone combined physical pre-treatment along with drying. The maximum change in color ?E = 14.75 and Chroma ?C = - 10.53 were obtained for the un-treated samples.