An intelligent hammer: a novel concept for automating nail and pile driving

Some interesting novel ideas on how the compliance needs of manipulators may be met by changing the stiffness of a structure have been presented in a paper by Ang and Andeen [1]. The purpose of the present note is to outline a novel concept for another variable-stiffness mechanism that may be useful in automating the process of driving nails or piles

Embedding negative structures to model holes and cut-outs

It has now been established that geometric boundary conditions and continuity conditions can be modelled by using either positive or negative stiffness or inertia type penalty term [1-5]. The experience of working with negative stiffness and inertial parameters has led to the question: what if both stiffness and mass were to be taken as negative? Changing the sign of all stiffness and inertial terms of a structure is simply equivalent to multiplying both sides of an eigenvalue equation by minus one, which does not change its frequencies or modes. Basically, a negative structure in such a sense has the same vibratory properties as that of its positive counterpart, although the structure itself may not have a physical meaning

The use of pseudo-inertia in asymptotic modelling of constraints in boundary value problems

In recent publications, the validity of using positive and negative inertial penalty parameters and the advantage of this approach over the conventional positive penalty function approach have been established for linear eigenvalue problems. This paper shows how this method may be applied to solve a boundary value problem. A steady-state 2-D heat transfer problem is used to demonstrate the method. First, the governing partial differential equation is modified by adding a pseudo-inertial term that results in an equation, which is mathematically identical to the equation governing the free vibration of a membrane. The essential boundary conditions of zero temperature along a specified line are imposed using inertial penalty parameters. The characteristic vibration modes found in this way are used to generate the complementary function to the heat transfer problem. This solution satisfies all natural boundary conditions (adiabatic) and zero temperature conditions using the inertial penalty parameter. To satisfy any additional temperature distribution imposed on the system, two sets of corrector terms are superimposed resulting in the final solution. The results are compared with constrained solutions obtained using the Lagrangian multiplier method and the ordinary penalty method

Transient vibration analysis of a completely free plate using modes obtained by Gorman's superposition method

This paper shows that the transient response of a plate undergoing flexural vibration can be calculated accurately and efficiently using the natural frequencies and modes obtained from the superposition method. The response of a completely free plate is used to demonstrate this. The case considered is one where all supports of a simply supported thin rectangular plate under self weight are suddenly removed. The resulting motion consists of a combination of the natural modes of a completely free plate. The modal superposition method is used for determining the transient response, and the natural frequencies and mode shapes of the plates used are obtained by Gorman's superposition method. These are compared with corresponding results based on the modes using the Rayleigh–Ritz method using the ordinary and degenerated free–free beam functions. There is an excellent agreement between the results from both approaches but the superposition method has shown faster convergence and the results may serve as benchmarks for the transient response of completely free plates

On the bipenalty method: why is it advantageous to add stiffness and mass

In a recent paper, Askes et al [1] proposed the simultaneous use of stiffness and inertia of large magnitude to model constraints in time domain analysis. From a frequency domain perspective, as stiffness and inertia have opposite effects on the natural frequencies, this seems counter-intuitive. With increasing stiffness, the natural frequencies either increase or remain unchanged, whereas the opposite is true for inertia. However, it can be shown, through very simple illustrative examples, that the natural frequencies and modes of continuous systems can be found in this way, and that there are advantages in using both stiffness and mass simultaneously

A passively adaptive screwdriver: a novel concept for controlling off-diagonal stiffness

A concept for an automated screw driving mechanism is presented. The proposed mechanism has a self-adjusting axial stiffness that depends on the torsional resistance against screwing. It delivers a greater axial thrust when the torsional resistance is greater, for example, towards the final stage of a screwing operation

European corn borer resistance in sorghum compared with maize

A total of 211 sorghum, Sorghum bicolor (L), genotypes were evaluated (1981, 1982, and 1983) for resistance to leaf feeding by 1st-generation European corn borer (ECB), Ostrinia nubilalis Hubner, larvae under heavy infestation conditions (ca. 750 eggs/plant). All sorghum hybrids were resistant. Some sorghum hybrids were not as resistant, however, as a highly resistant inbred line of maize, Zea mays L;First-generation larval mortality was rapid on four sorghum hybrids (92.2 - 97.7% mortality within 6 days after egg hatch), but larval mortality was not as rapid on four sorghum hybrids as was larval mortality on a resistant maize inbred (99.1 - 99.7% mortality within 6 days after egg hatch). The majority of 22,827 1st-generation larvae fed on leaf tissue in the moist area deep in the whorl of sorghum and maize plants. Resistance in sorghum, as in maize, to 1st-generation ECBs, therefore, is resistance to leaf feeding (a high level of antibiosis against 1st- and 2nd-instar larvae). Dried-ground leaves (substituted for wheat germ in a meridic diet) of resistant genotypes of sorghum and maize had no deleterious effect on survival and development of ECB larvae compared with a diet containing leaves of susceptible maize and compared with a standard wheat germ diet;Second-generation larval mortality was rapid on four sorghum hybrids (93.9 - 98.9% mortality within 6 days after egg hatch) and on two resistant maize inbreds (92.6 - 97.8% mortality within 6 days after egg hatch). The majority of 33,690 2nd-generation larvae fed on sheath-collar tissue through 35 days after egg hatch of sorghum plants and through 15 days after egg hatch on maize plants. Resistance in sorghum to 2nd-generation ECBs as in maize, therefore, is resistance to sheath-collar feeding (a high degree of antibiosis against 1st- and 2nd-instar larvae)

Vibration Behaviour Of In-plane Loaded Thin Rectangular Plates With Initial Geometrical Imperfections

The effect of in-plane loading on the natural frequencies of simply supported thin rectangular plates with initial geometrical imperfection is investigated theoretically and experimentally. It is shown that the natural frequencies depend on applied in-plane load, initial geometrical imperfection and the in-plane boundary conditions.;In the theoretical analysis, the natural frequencies, out-of-plane static displacements and in-plane stress distribution are calculated using the Rayleigh-Ritz minimization technique. A concept of \u27connection coefficients\u27 has been used to reduce the computational work. In this concept, the relationship between the out-of-plane and in-plane displacement coefficients are first determined by solving the equations resulting from the minimization of the total potential energy with respect to the in-plane displacement coefficients. This relationship is then substituted into the equations obtained by minimizing the total potential energy with respect to the out-of-plane displacement coefficients.;In the experimental side of the work, tests were carried out on several thin (thickness ranging from 0.56 mm to 1.15 mm) mild steel plates (300 mm x 250 mm). Uniaxial in-plane loading was applied through two \u27V\u27 grooved edge beams. The other two edges were supported between two rows of ball bearings placed in \u27V\u27 grooves, carefully adjusted to minimize the friction along these edges.;The agreement between the measured and calculated values of natural frequencies, out-of-plane central displacements and static strain distribution is very good. An interesting observation from the result is that a simple approximate linear relationship between a load-frequency parameter (involving the fundamental natural frequency and the state of in-plane stress) and the square of the central deflection is obtained. Further experimental and theoretical work in this field is strongly recommended

A Study on the Influence of Human Resources Practices on Turnover Intention Among a Telecommunication Company Employees

While performing their duties in an organization, an employee tied up to a human resource practices which consists of internal career opportunity, training, result oriented appraisals, Employment security, participation and job description to retain in an organization. This research title is aimed to determine the influences of internal career opportunity, training, result oriented appraisals, employment security, participation and job description on turnover intention. The objective of this study is; to understand the influence of the selected human resource practices on turnover intention. A total of 169 questionnaires were distributed to one of the selected Telecommunication company. Data were analyzed using both descriptive and inferential statistical analysis to interpret data. Research fmdings revealed there was turnover intentions exist among the respondents. Significant values for each element in independent variable which the item of reward such as result oriented appraisal, training, and participation. The higher significant value of independent variables are result oriented appraisal and item benefits, 0.538 > 0.05

Evaluation Of Cholera Vaccine Candidates VCUSM2 (0139), VCUSM4 (El Tor) And Its Bivalent Vaccine Formulation [RA644.C3 K96 2008 f rb].

Kolera pernah berlaku di hampir kesemua pelusuk dunia dan dua kumpulan-sera telah dikenalpasti sebagai penyebab kolera iaitu V. cholerae O1 and V. cholerae O139. Cholera has been implicated in many parts of the worlds and two serogroup identified for causing epidemic cholera are the V. cholerae O1 and V. cholerae O139