Search results

THE use of liquid oxygen as an oxidizer for various fuels in liquid rocket propellent systems is not new. Professor Goddard used liquid oxygen in his rocket experiments and the well known German V‐2 rockets used this material as an oxidizer. However, its effect on non‐metallic materials ordinarily used in rocket systems was not investigated until recent years. This investigation was prompted by phenomena which had been experienced by rocket engine and rocket aircraft manufacturers and by suppliers of the material. It was observed that when some organic materials came in intimate contact with liquid oxygen they became prone to detonation when subjected to certain impact energies. This was undoubtedly due to the formation of unstable organo‐peroxide compounds which when impacted released high levels of energy resulting in an explosion. Specifically, when liquid oxygen was accidently spilled on asphalt and inadvertently stepped on, the asphalt would often explode. Also, leather gaskets immersed in liquid oxygen and subjected to surge impact detonated with disastrous effects.

With the pressing need for environmental conservation, regulatory authorities are actively looking for measures to prevent global warming. In the proposed inventory model for deteriorating items, demand is dependent on the selling price and green technology investment (or carbon reduction investment) for the green product (GP), as well as an investment in price-based preservation technology to slow down the pace of deterioration. Furthermore, emission reduction measures are put in place to reduce carbon emissions (CEs).

The current study executed a thorough literature review to determine how to improve supply chain management performance. Furthermore, assumptions are made to fill research gaps, and a mathematical model is created to address the problem mentioned above. To collect the data, the available inventory literature was reviewed. Additionally, numerical illustrations and sensitivity analyses are presented to emphasize the model's robustness.

The research indicates that it is more prudent to invest in preservation technology based on its selling price in order to control the rate of deterioration. In addition, the proposed model facilitates the management of deteriorated waste through salvage trading and emission reduction investment. The findings validate sustainable practices with a 20.86% increase in profit and a 21.4% decrease in CEs, thereby signifying environmental and economic benefits.

The proposed model enhances understanding of the impact of investments in price-based preservation technology and carbon reduction efforts on consumer perceptions of their intention to purchase GPs. Moreover, the study provides valuable insights by identifying important recommendations for policymakers regarding areas that require further investigation. This guideline can help identify both current and unexplored gaps, enabling researchers to direct future research efforts toward producing new products.

In the paper the optimization procedure of a direct current motor with a hybrid excitation has been presented. The excitation system consists of a shunt field winding disposed around field pole and permanent magnet, both acting in parallel. The field distribution in motor for various magnet and field pole dimensions has been determined using finite element method. The flux linkage with the armature winding has been computed. Demagnetizing effect of armature current was taken into account. The optimal permanent magnet and the field pole dimensions, ensuring minimum total cost of purchase and work during assumed period of time were calculated. Motor characteristics e.g. rated torque, rated current, speed regulation limit were used as constraints. In worked up algorithm and computer program Carroll internal penalty function method was used. Some basic suggestions tor design of optimal hybrid excited dc motors with parallel permanent magnet and electromagnetic excitation are given.

In the course of development of human communities towards industrially advanced societies of today, there have been changes not only in economic conditions in the majority of fields of human activity but also in the ways of providing for food, which went hand in hand with changes in living conditions. Large‐scale industrial production has brought about major changes in the way of life of the population. The development of industrial agglomerations results in a growing number of city dwellers, most of whom have no chance of producing foodstuffs of their own in kind. The distance between residential and industrial areas has been growing, the number of employed women has risen considerably. These are but a few factors affecting the way of boarding, particularly in households.

By hot‐dip galvanizing steel and iron objects and constructions the corrosion resistance obtained is already very high and in the majority of cases no paint system is required as a supplementary protective coating. In practice, however, six cases can be shown where it is necessary or desirable to paint hot‐dip galvanized steel.

Casual inexcused absenteeism is considered to be one of the major contributing factors for increased operating costs for companies which have work flowing through a group of workers, each worker performing an operation on it and then passing it on to the next. Many researchers have indicated that in most of the cases, workers are not assigned to perform the tasks for which they have the requisite capabilities. The resulting stress on the worker is considered to be a major factor causing the worker to absent from work. Psychologists have developed many measures of human skills. Industrial Engineers and others concerned with the prediction of human performance have developed predetermined motion time systems. Well tested skill tests, i.e., eye‐hand coordination, finger dexterity, decision making, etc. (a battery of twelve such tests), and breaking down manual tasks into different categories such as amount of control needed over motions, precision required, manipulation of material involved, etc. (a total of thirty‐two job requirements), have resulted in a general scheme of “scoring.” A computer program has been developed to match the worker capabilities to the task requirements. It is hoped that such a scheme, in addition to minimizing absenteeism, may result in improved product quality.

The purpose of this paper is to find an omnidirectional robust gust response stabilization (GRS) scheme with anti-disturbance and state-limited features.

Disturbance observer and barrier Lyapunov techniques, which can, respectively, estimate the lumped disturbances of the dynamic system in real-time and ensure the middle states within some prescribed ranges according to some flight safety indexes.

In the existing literature, almost all of the GRS controllers are either only for the longitudinal dynamics or only for the latitudinal dynamics. Few studies have considered the gust response alleviation problem with omnidirectional wind disturbance and full aircraft model.

This paper proposes a fresh scheme to deal with a more holistic GRS problem; the disturbance observer based (DOB) barrier Lyapunov backstepping longitudinal controller has been put forward; DOB nonlinear dynamic inversion to handle the multi-input-multi-output lateral dynamics; and to closely connect the two loops of the latitudinal dynamics, a manipulating variable conversion method is proposed.

The purpose of this paper is to identify how three types of socialization tactics – content, context and social tactics – influence fit perceptions, and then how three types of fit perceptions – person–organization (P–O) fit, person–job (P–J) fit and person–group (P–G) fit – mediate the relationship between socialization tactics and positive socialization outcomes: organizational commitment, job satisfaction and intent to quit.

Responses from participants – 207 Korean youth workers – were subjected to ordinary least squares path analyses with bootstrapping to test the hypotheses.

First, this study found that socialization tactics promote youth workers’ perceived fit with organization, job, and people. Then, the mediation model showed that content socialization tactics do not influence dependent variables (socialization outcomes) through mediators (fits), while context tactics influence through perceived P–O fit and P–G fit for organizational commitment only, and social tactics through perceived P–O, P–J and P–G fit for organizational commitment, job satisfaction and intent to quit.

The results of this study suggest that institutionalized social tactics can serve as a key socialization method for new employees. In addition, youth organizations need to implement jointly formal and collective training programs with follow-up social workplace learning (e.g. mentoring and study circle) to help newcomers share the values of the organization and integrate well into it.

This study contributes for understanding the socialization process of new employees working in educational and social work fields and role of fit perception between socialization tactics and their career successes.

Gives a bibliographical review of the finite element methods (FEMs) applied for the linear and nonlinear, static and dynamic analyses of basic structural elements from the theoretical as well as practical points of view. The range of applications of FEMs in this area is wide and cannot be presented in a single paper; therefore aims to give the reader an encyclopaedic view on the subject. The bibliography at the end of the paper contains 2,025 references to papers, conference proceedings and theses/dissertations dealing with the analysis of beams, columns, rods, bars, cables, discs, blades, shafts, membranes, plates and shells that were published in 1992‐1995.

This paper focuses on how the producer inspires his cooperative research partner to reduce carbon emission, by developing a menu of incentive contracts both in research and development (R&D) stage and recycling stage.

The proposed mechanism combines the researcher with the producer in a two-staged closed-loop system. Based on the concept that the producer takes the environmental responsibility, this paper designs a dynamically updating contract for the producer to encourage low-carbon efforts. Meanwhile, the producer offers a menu of contracts against the asymmetric information, that is, the R&D partner owns private information on his low-carbon R&D capability. According to incentive mechanism, the researcher decides whether to tell the truth and how much effort she would exert in R&D and recycling stages.

Discriminating between different types of researchers hurts the producer’s profit. But the updated screening contract can inspire researchers to tell the truth and is beneficial in reducing carbon emissions in the two stages. The results give the optimal solutions of the incentive mechanism. The low-type researcher only obtains reservation profit, whereas the high-type is given more to induce the information.

This paper proposes a strategy of updating the contract factors for avoiding adverse selection and moral hazard. Considering the environmental responsibility of waste products, the producer would like to encourage low-carbon designs among the R&D partners in a closed-loop supply chain.