scholarly journals The sensitiveness of explosives - The effect of compression on the sensitiveness of initiators

The sensitiveness of the following initiators has been compared when used loose, and when compressed up to 2300 kg./cm. Crystalline Service azide (crystals 75 X 10-4 cm.). Powdered Service azide (fragments 1 to 25 x 10~4 cm.). Dextrinated lead azide. Mercury fulminate. Sensitiveness to heat was measured by determining the induction period at various temperatures, and also by evaluating threshold temperatures below which no detonation was observed for various masses of initiators. Tests were also made to see how far the action of flame, and of percussion, could be correlated with the action of heat on these initiators. Compression reduces the induction period in all cases, but the values of E and B (see text) are differently affected in the case of different initiators. Compression also lowers the threshold temperature below which a given mass of initiator will not detonate. Thus in all cases sensitiveness to heat is increased by compression. On the other hand, compression lessens the sensitiveness of mercury fulminate to flash and percussion, corresponding with the well-known phenomenon of ‘dead-pressing’. If anything, compression increases the sensitiveness of lead azide to flash and percussion. A new detonation mechanism has been observed for both service and dextrinated lead azides. The experimental results throw further light on the build-up of the detonation wave in explosives. When the volume of explosive ‘primarily’ involved in the sensitiveness phenomenon is small, as is usually the case for initiators, the mechanism of build-up differs from the ‘self-heating’ mechanism which may overtake it with larger volumes of explosive. A simple explanation is suggested for the ‘dead-pressing’ of explosives, which is to be expected when ‘self-heating’ is the mechanism controlling the build-up of detonation.

2020 ◽  
Vol 1004 ◽  
pp. 953-959
Author(s):  
Benedikt Lechner ◽  
Yaren Huang ◽  
Stefan Schaub ◽  
Gerhard Wachutka

The activation of bipolar conduction was investigated for two 4H-SiC 10 kV JBS-diodes which differ in the area ratio between p-doped and n-doped regions (Ws/WPin). Quasi-static measurements at low electric current densities (j < 2.5 Acm-2) were performed in a temperature range between 25°C and 500°C. The lower ratio (Ws/WPin) leads to a higher threshold voltage. On the other hand lower electric power density is neccessary to trigger temperature enhanced bipolar activation. Moreover, the lower ratio improves the leakage currents in blocking direction. Dynamic surge current investigations were performed in a temperature range between 25°C and 250°C. The turning voltages, which indicate the transition from unipolar to bipolar conduction, are lower for the diode with smaller ratio (Ws/WPin) but the self-heating of the device is more severe in comparison to the other diode with the larger ratio. Both devices are stable under extreme conditions (high temperatures/ surge current) and exhibit special benefits for different applications.


1947 ◽  
Vol 25b (6) ◽  
pp. 548-565 ◽  
Author(s):  
A. S. Hawkes ◽  
C. A. Winkler

The minimum explosion temperatures for service and dextrin azides (about 315 °C. and 275 °C., respectively) are increased considerably by increase of surface: volume ratio of the container and by compressing or wetting the charge with dibutyl phthalate before explosion. When wetted, the two azides were found to be similar in respect of minimum explosion temperatures and induction periods prior to explosion. Sensitization of service azide by preheating was found to be permanent. A limit to sensitization below the minimum explosion temperature was observed, and probably exists also for sensitization above this temperature. Wetting the charge with phthalate nullifies the sensitization. Although dextrin azide alone is more thermally sensitive than service azide, mixtures of the two containing 70% or more service azide show a sharp change to service azide properties; the mixtures apparently are not exploded by the dextrin azide they contain. The value of E in the expression [Formula: see text] + constant, where t is the induction period, has been determined for both the initial and final stages of reaction preceding explosion and found to be essentially unaltered. Minimum explosion temperature of single large crystals was shown to increase with crystal size. The data are interpreted as showing that the thermal explosion of lead azide may result from self-heating, the heat of the pre-explosion reaction not being sufficiently dissipated from the material.


2019 ◽  
Vol 78 (1-2) ◽  
pp. 69-75 ◽  
Author(s):  
Mikaël De Clercq ◽  
Charlotte Michel ◽  
Sophie Remy ◽  
Benoît Galand

Abstract. Grounded in social-psychological literature, this experimental study assessed the effects of two so-called “wise” interventions implemented in a student study program. The interventions took place during the very first week at university, a presumed pivotal phase of transition. A group of 375 freshmen in psychology were randomly assigned to three conditions: control, social belonging, and self-affirmation. Following the intervention, students in the social-belonging condition expressed less social apprehension, a higher social integration, and a stronger intention to persist one month later than the other participants. They also relied more on peers as a source of support when confronted with a study task. Students in the self-affirmation condition felt more self-affirmed at the end of the intervention but didn’t benefit from other lasting effects. The results suggest that some well-timed and well-targeted “wise” interventions could provide lasting positive consequences for student adjustment. The respective merits of social-belonging and self-affirmation interventions are also discussed.


Author(s):  
Stefan Krause ◽  
Markus Appel

Abstract. Two experiments examined the influence of stories on recipients’ self-perceptions. Extending prior theory and research, our focus was on assimilation effects (i.e., changes in self-perception in line with a protagonist’s traits) as well as on contrast effects (i.e., changes in self-perception in contrast to a protagonist’s traits). In Experiment 1 ( N = 113), implicit and explicit conscientiousness were assessed after participants read a story about either a diligent or a negligent student. Moderation analyses showed that highly transported participants and participants with lower counterarguing scores assimilate the depicted traits of a story protagonist, as indicated by explicit, self-reported conscientiousness ratings. Participants, who were more critical toward a story (i.e., higher counterarguing) and with a lower degree of transportation, showed contrast effects. In Experiment 2 ( N = 103), we manipulated transportation and counterarguing, but we could not identify an effect on participants’ self-ascribed level of conscientiousness. A mini meta-analysis across both experiments revealed significant positive overall associations between transportation and counterarguing on the one hand and story-consistent self-reported conscientiousness on the other hand.


2019 ◽  
Vol 50 (2) ◽  
pp. 80-93
Author(s):  
Jort de Vreeze ◽  
Christina Matschke

Abstract. Not all group memberships are self-chosen. The current research examines whether assignments to non-preferred groups influence our relationship with the group and our preference for information about the ingroup. It was expected and found that, when people are assigned to non-preferred groups, they perceive the group as different to the self, experience negative emotions about the assignment and in turn disidentify with the group. On the other hand, when people are assigned to preferred groups, they perceive the group as similar to the self, experience positive emotions about the assignment and in turn identify with the group. Finally, disidentification increases a preference for negative information about the ingroup.


2014 ◽  
Vol 4 (2) ◽  
Author(s):  
Tamara Feldman

This paper is a contribution to the growing literature on the role of projective identification in understanding couples' dynamics. Projective identification as a defence is well suited to couples, as intimate partners provide an ideal location to deposit unwanted parts of the self. This paper illustrates how projective identification functions differently depending on the psychological health of the couple. It elucidates how healthier couples use projective identification more as a form of communication, whereas disturbed couples are inclined to employ it to invade and control the other, as captured by Meltzer's concept of "intrusive identification". These different uses of projective identification affect couples' capacities to provide what Bion called "containment". In disturbed couples, partners serve as what Meltzer termed "claustrums" whereby projections are not contained, but imprisoned or entombed in the other. Applying the concept of claustrum helps illuminate common feelings these couples express, such as feeling suffocated, stifled, trapped, held hostage, or feeling as if the relationship is killing them. Finally, this paper presents treatment challenges in working with more disturbed couples.


Author(s):  
Milen Dimov

The present study traces the dynamics of personal characteristics in youth and the manifested neurotic symptoms in the training process. These facts are the reason for the low levels of school results in the context of the existing theoretical statements of the problem and the empirical research conducted among the trained teenagers. We suggest that the indicators of neurotic symptomatology in youth – aggression, anxiety, and neuroticism, are the most demonstrated, compared to the other studied indicators of neurotic symptomatology. Studies have proved that there is a difference in the act of neurotic symptoms when tested in different situations, both in terms of expression and content. At the beginning of the school year, neurotic symptoms, more demonstrated in some aspects of aggressiveness, while at the end of school year, psychotism is more demonstrated. The presented summarized results indicate that at the beginning of the school year, neurotic symptoms are strongly associated with aggression. There is a tendency towards a lower level of social responsiveness, both in the self-assessment of real behavior and in the ideal “I”-image of students in the last year of their studies. The neurotic symptomatology, more demonstrated due to specific conditions in the life of young people and in relation to the characteristics of age.


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