For a description of the wood of the conifers see Bulletin 101 of the Department of Agriculture. RESISTANCE OE HARDWOODS TO CREOSOTE. 3 wood. These rings are more or less conspicuous in the hardwoods of temperate regions, especially in those of the ring-porous group. In general, the springwood is more open and has fewer thick-walled cells than the summerwood. Medullary rays.-The medullary rays (silver grain) which extend like the spokes in a wheel from the bark toward the pith at the center of the tree, are very conspicuous in some hardwoods, such as oak, beech, and sycamore.. MICROSCOPIC STRUCTURE. The microscopic structure of the hardwoods is illustrated b}^Plates I, II, III, and IV. Plate I is a photograph, taken through the microscope, of a section of maple. This wood belongs to the diffuse-porous group of hardwoods, which is so called because the pores or vessels (V) are scattered with considerable uniformity throughout the annual ring (AE). In this group the pores in the springwood (SP) are generally but little larger than those in the summerwood (SW). Plate II shows red oak, an example of ring-porous wood. In the springwood of this species there is a noticeable group of large pores. When seen on the cross-section of a log these make conspicuous concentric rings around the pith. In this wood the pores are not distributed uniformly through the annual ring and there is a very considerable difference in the sizes of those in the springwood and the summerwood. The springwood pores in a ring-porous wood are usually considerably larger than the corresponding pores in a diffuseporous wood. Although these two species are typical of the two groups, yet in each group it is possible to find variations from the types of structure shown. Some diffuse-porous woods, for example, are more porous than maple ; that is, t\\Qj have more pores per square inch in proportion to the number of fibers and the like than others do. Some of the ring-porous woods have the large springwood vessels blocked with cell-like growths called tyloses 1 (T, Plate IV). These are visible to the naked eye as glistening fragments in the pores of such woods as white oak or hickory. T3 r loses are also present in the diffuse-porous woods, although somewhat less abundantly and uniformly developed. They occur in the vessels which are not active in the transfer of sap ; therefore, they .are most numerous and completely developed in the older sapwood and the heartwood. Medullary rays.-The medullary rays (ME) are generally rather conspicuous in the hardwoods, although in woods like aspen and 1 " Tyloses : Their occurrence and practical significance in some American woods,"

This paper demonstrates the effectiveness of a Modified Linear Integral Resonant Controller (MIRC) based on its original LTI cousin, known just as the 'IRC', for suppressing Jump-Phenomenon and hysteresis found in Micro-Cantilevers. A Method of Multiple Scales frequency response is derived, explored and compared with a Runge-Kutta based numerical integration method in order to understand any shortcomings in approximate analytical methods for the analysis of closed-loop nonlinear systems with the inclusion of a stability analysis. It is found that there exist some mild inconsistencies when comparing closed-loop Method of Multiple Scales to traditional numerical integration. A suitably designed Modified Integral Resonant Controller is implemented in closed-loop. Both analytical and numerical results agree with each other and show significant damping performance. Efficacy of the proposed control scheme is validated via frequency response plots, phase portraits and quiver plots.

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In this work, performance of a modified-integral resonant controller with integral tracking is investigated numerically under the effects of actuator delay and actuation constraints. Actuation delay and constraints naturally limit controller performance, so much so that it can cause instabilities. A 2-DOF drill-string m with nonlinear bit–rock interactions is analysed. The aforementioned control scheme is implemented on this system and analysed under the effects of actuation delay and constraints and it is found to be highly effective at coping with these limitations. The scheme is then compared to sliding-mode control and shows to be superior in many regimes of operation. Lastly, the scheme is analysed in detail by varying its gains as well as varying system parameters, most notably that of actuation delay.

Petrol is one of the most commonly used liquid accelerants in arson cases. It is identified by the presence of an abundance of aromatic compounds whose peaks cluster in specific patterns. The positive identification of these target compounds suggests the presence of the petrol in the debris. This information can assist a fire investigator in determining the cause of the fire, including whether or not arson is suspected. The current research aims at studying the legitimate background products in fire debris, including their identification and characterisation. A range of substrates commonly encountered at fire scenes in Mauritius were analysed in the presence and absence of petrol using the passive headspace absorption method. In unburnt samples, a number of interfering products were identified and some of the hydrocarbons liberated were those commonly found in petrol. When comparing the results of the burnt with the unburnt samples, it was found that only a small proportion of the volatiles detected in the burnt items were due to pyrolytic products and the rest were attributed to residues originally present in the unburnt items. Samples analysed in the presence of petrol, revealed that the concentration of these interfering products were below the detection limit for the accelerant and thus did not cause misinterpretation of the data.