Шляхи підвищення ефективності використання виробничих ресурсів сільськогосподарських підприємств

Single-phase polycrystalline samples and single crystals of the complex boride phases Ti8Fe3Ru18B8 and Ti7Fe4Ru18B8 have been synthesized by arc melting the elements. The phases were characterized by powder and single-crystal X-ray diffraction as well as energy-dispersive X-ray analysis. They are new substitutional variants of the Zn11Rh18B8 structure type, space group P4/mbm (no. 127). The particularity of their crystal structure lies in the simultaneous presence of dumbbells which form ladders of magnetically active iron atoms along the [001] direction and two additional mixed iron/titanium chains occupying Wyckoff sites 4h and 2b. The ladder substructure is ca. 3.0 Å from the two chains at the 4h, which creates the sequence chain–ladder–chain, establishing a new structural and magnetic motif, the scaffold. The other chain (at 2b) is separated by at least 6.5 Å from this scaffold. According to magnetization measurements, Ti8Fe3Ru18B8 and Ti7Fe4Ru18B8 order ferrimagnetically below 210 and 220 K, respectively, with the latter having much higher magnetic moments than the former. However, the magnetic moment observed for Ti8Fe3Ru18B8 is unexpectedly smaller than the recently reported Ti9Fe2Ru18B8 ferromagnet. The variation of the magnetic moments observed in these new phases can be adequately understood by assuming a ferrimagnetic ordering involving the three different iron sites. Furthermore, the recorded hysteresis loops indicate a semihard magnetic behavior for the two phases. The highest Hc value (28.6 kA/m), measured for Ti7Fe4Ru18B8, lies just at the border of those of hard magnetic materials

Characterization of the Ngouache Landslide by Geotechnical Survey (Bafoussam, Cameroon)

The heavy rainfall during the night of October 28-29, 2019, caused a landslide in the Ngouache 4 neighborhood in Bafoussam in the West Cameroon region. This landslide caused 43 deaths, several missing persons and the destruction of several houses and plantations. The present investigation attempts to find the causesof this landslide. First, the landslide area was identified and heavy dynamic penetrometer surveys were conducted. Next, intact and reworked samples were taken and, finally, slopes were measured on the slide area to determine the soil parameters. The results of the heavy dynamic penetrometer showed the presence of altered clay layers which, when saturated, exert hydrostatic pressure and unbalance the soil. The granulometric analysis noted a soil with more than 50% of grains of ϕ>80µm with liquidity limits between (50-65.3%), a consistency index between (1.01-1.24), a low cohesion between (0.22-0.30 bars) for a high internal friction angle (20.72°-23.86°), slopes between 48° and 56° and a degree of saturation Sr between (80.5° and 139.9°). These characteristics associated with the large water columns of the night of October 28 to 29, 2019 demonstrated that the water had exerted a hydrostatic pressure having made the clay material reach the limit of plasticity to the creep and raised the level of the water table. Thistherefore promoted the saturation of the substrate yet the increase in the water content reduces the cohesion of the materials and that triggered the saturation at the origin of this deadly slide. The results of the present research may help the public authorities in the decision making regarding the characterization and the securing of risk zones

Damage process in a discrete disordered model and consequences on disordered composites

No Abstract Available Journal des Sciences pour l\'Ingenieur Vol 5 2005: 53-5

Study of Water Absorption in Raffia vinifera Fibres from Bandjoun, Cameroon

The study is focused on the water diffusion phenomenon through the Raffia vinifera fibre from the stem. The knowledge on the behavior of those fibres in presence of liquid during the realization of biocomposite, is necessary. The parameters like percentage of water gain at the point of saturation, modelling of the kinetic of water absorption, and the effective diffusion coefficient were the main objectives. Along a stem of raffia, twelve zones of sampling were defined. From Fick’s 2nd law of diffusion, a new model was proposed and evaluated compared to four other models at a constant temperature of 23°C. From the proposed model, the effective diffusion coefficient was deduced. The percentage of water gain was in the range of 303–662%. The proposed model fitted better to the experimental data. The estimated diffusion coefficient was evaluated during the initial phase and at the final phase. In any cross section located along the stem of Raffia vinifera, it was found that the effective diffusion coefficient increases from the periphery to the centre during the initial and final phases