Adult cold tolerance and potential North American distribution of Myllocerus undecimpustulatus undatus (Coleoptera: Curculionidae)

Cold tolerance and potential distribution of Myllocerus undecimpustulatus undatus Marshall, a polyphagous pest in the United States, were investigated. Adult survivorship after 2 days at 0 °C and − 5 °C averaged 60% and 18%, respectively. Four days of exposure resulted in survivorship of 11% at 0 °C and 4% at − 5 °C, respectively. Summer-collected weevils at − 5 °C through repeated cold exposure of 2 h survived 3 times longer than those subjected to sustained cold period of 10 h. Leaf consumption did not differ among summer-collected weevils at constant 20 °C and repeated cold exposure treatments; weevils under sustained cold exposure consumed less than weevils in repeated cold exposure treatments. Leaf area consumed after cold exposure was 2–4 times greater in winter-collected weevils compared to summer-collected weevils. Leaf consumption by winter-collected weevils decreased as the number of repeated cold exposure periods increased. Locality data from collections in Florida during 2000–2012 were used to produce a correlative model complemented by a mechanistic model from the cold tolerance data to project the potential distribution of M. undecimpustulatus undatus in North America. The models support the hypothesis that M. undecimpustulatus undatus could spread to areas of the southeastern and western United States. The predicted northern distribution followed an isothermal line about 33° North. The niche model defined an area along the western Gulf Coast as unsuitable for the weevil, possibly because the area receives greater annual rainfall than other areas of the southeastern United States and has aquic or udic soil unlike the well-drained sandy soil of peninsular Florida.

Simulasi numerik kombinasi perpindahan panas konveksi alami dan radiasi pada square cavity

Natural convection is very important in some cases such as glass windows, solar collectors, electronic measuring devices (cooling devices for electronic instruments) and building materials that use insulation. In this research, will be seen the phenomenon of natural convection that occurs in square cavity. The method used for simulation is computational fluid dynamics or CFD. The model used is the 2D cavity model. In this simulation the value of Rayleigh Number (Ra) was varied i.e. 103,104,105 and 106. From this research, it is found that the higher the value of Ra in cavity, the higher the value of the average Nusselt Number (𝑁̅𝑢 ) on the wall which has a high temperature. Ra = 103 so that 𝑁̅𝑢 = 1.17. Ra =104, so that 𝑁̅𝑢 = 2.2. Ra = 105, so that 𝑁̅𝑢 = 4.47. Ra = 106, and then so that 𝑁̅𝑢 = 8.95. Based on the value and contour of the flow the smaller the Ra value in the square cavity, the isothermal line phenomenon that appears will be more vertical. The greater the Ra value in the cavity, the contour of the stream function will change to an ellipse and finally two vortices will appear.Keywords: Numerical simulation, konveksi, radiasi, square cavity.

IMPROVEMENT OF POWER SUPPLY OUTPUT VOLTAGE TEMPERATURE STABILITY BY MEANS OF ANISOTROPY OF ITS CONSTRUCTION THERMAL FIELD

The article considers the method of thermal stabilization for precision power supply output voltage by means of anisotropy of the construction thermal field. Interdependency between schematic and design-topological aspects of precision power supply temperature assurance is shown. In theoretical part of the paper, the concept of electronic component local group arranged on isothermal line of the supporting structure plane is introduced. The local group characteristics and conditions for ensuring topological thermocompensation are formulated. The authors propose the solution for two basic applied problems that provides temperature stabilization of electronic devices output parameters by topological temperature compensation using regression analysis. The experimental part of the paper provides the analysis of the output voltage temperature stability for two design versions which differ by availability of topological thermocompensation. The reason of foreign element base use for the purposes of the experimental part of the study is explained. It is shown that the global mathematical model for providing topological thermocompensation for a design option with improved temperature stability is the temperature error equation. A comparative analysis of the two construction options shows 8 % improvement of output voltage temperature stability due to topological thermocompensation. The obtained result may prove to be satisfactory under technical assignment for the use of a different element base and / or other methods of thermal stabilization.

Soil freezing and the depth of spread foundations

This paper presents the possibility for setting heated building foundations at a depth lower than the level of „zero” isothermal line. In order for the foundation not to be susceptible to damage due to its exposure to negative temperatures, an appropriate thermal insulation was proposed. For the suggested thermal insulation - by means of numerical methods - a calculation of temperature distribution in the vicinity of the foundations was carried out. Based on the analysis of the obtained results, an optimal setting depth for insulated foundations was proposed.

PHASE EQUILIBRIUM IN YbTe–Yb3Ge5 SYSTEM

For citation:Mukhtarova Z.M. Phase equilibrium in Ybte–Yb3Ge5 system. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 1. P. 64-67.Study of properties of semiconductors developed in close connection with their technical applications. The present work was devoted to study of phase equilibria and character of interaction in YbTe–Yb3Ge5 system. The section of YbTe–Yb3Ge5 in ternary system Ge–Te–Yb is not only scientific, but also practical interest. The section of YbTe–Yb3Ge5 was studied by methods of physical-chemical analysis: differential-thermal (DTA), high temperature differential-thermal (HTDT), X-ray phase, microstructural analysis (MSA), as well as measurement of density and micro hardness. DTA was performed with pyrometer HTP-75 in quartz ampoule pimped off till 0.1333 Pa. HTDT was performed with HTDT-8m (Tmelt.≥1500÷2000K) by analogical method. X-ray phase analysis was performed by powder method with X-ray diffractometer DRON-2 (CuKα- radiation with Ni-filter). MSA was performed with microscope MIM 8. Micro hardness of alloys was measured with micro hardness tester PMT-3.Density of alloys was determined by pycnometer test. During investigations of the system we used germanium B–4, tellurium B–3, ytterbium Yb–1. Alloys were synthesized at 1450–1700 K temperature range and at this temperature ampoule was kept 5–6 h. Cooling was performed slowly. DTA shows that on thermograms of alloys of the system have two effects. Obtained effects are endothermic reversible.For confirming the data of DTA, microstructural analysis, as well as measurement of micro hardness were performed with X-ray analysis. As the data show, at the concentration of 15–80 mol% of Yb3Ge5 monotectic conversion occurs which is confirmed with isothermal line at 1025 K. Thus, it was established that the section of 4YbTe–Yb3Ge5 is quasibinary cross-section of ternary system Ge–Te–Yb and its diagram is related to eutectic type with monotectics.Eutectic of the system 4YbTe–Yb3Ge5 corresponds to composition of 85% mol% of Yb3Ge5 and temperature of 915 K.

Vertical Movement of Isothermal Lines in Water

We experimentally investigated the development and vertical movement of isothermal lines in cooling columns of confined water. The isothermal line develops spontaneously whenever the bottom of the column cools to ∼4°C before the top. The width of these lines was typically less than 1 cm, with up to a 3°C thermal gradient across these lines. The velocity was inversely proportional to the diameter of the column. The velocity was 1.4±0.1 cm/min when the column diameter was 2.2 cm, and decreases to 0.4±0.1 cm/min when the diameter was increased to 12.5 cm. Data presented here also raise serious questions about the claim of new phase transitions in water made by Esposito et al. (2008, “Mpemba Effect and Phase Transitions in the Adiabatic Cooling of Water Before Freezing,” Physica A, 387, pp. 757–763).

Effects of Lubricant Rheology and Kinematic Conditions on Micro-Elastohydrodynamic Lubrication

The effects of lubricant rheology and surface kinematic conditions on micro-elastohydrodynamic (EHD) lubrication are analyzed under isothermal line-contact conditions. Micro-EHD lubrication is modeled by introducing a surface irregularity in the form of an asperity or a furrow into the contact zone. Under simple sliding conditions, the pressure generated in the vicinity of the irregularity and the resulting surface deformation depend strongly on the lubricant rheology. The surface kinematic conditions have profound effects on micro-EHD lubrication. In general, a stationary surface irregularity produces a relatively strong downstream effect when it is in the inlet region of the contact, and a moving surface irregularity produces a relatively strong upstream effect after it enters the Hertzian central region. The simulated results agree qualitatively with previous experimental measurements and observations.