UTJECAJ COVID-19 KRIZE NA RUDARSKU DJELATNOST U REPUBLICI HRVATSKOJ

Mining as a human activity shares the fate of humanity in all global situations that affect the planet. These are, to a lesser extent, positive effects such as the opening of the world market, the industrial revolution, etc., and, to a greater extent, negative effects such as various conflicts or pandemics that have a global character. The COVID-19 pandemic has had an unprecedented impact on all sectors of human society, justifying a scientific interest in assessing its impact at global and local levels. Recently, the World Health Organization declared the end of the pandemic, after which the Croatian government did the same. This also marks the end of the research period for the preparation of this paper. The paper is about the study of the impact of the pandemic on the Croatian mining sector in Croatia. In addition to statistical data on production and the number of employees in the mining sector, the results of a survey of economic entities and conclusions about the management of companies in crisis situations were processed.Rudarstvo kao ljudska djelatnost dijeli sudbinu čovječanstva u svim globalnim situacijama koje pogađaju planet. To su manjim dijelom pozitivni učinci poput otvaranja svjetskoga tržišta, industrijske revolucije i sl., a većim dijelom negativni učinci poput raznih sukoba ili pandemija koje imaju globalni karakter. COVID-19 pandemija imala je nezapamćen utjecaj na sve sektore društva, što opravdava znanstveni interes za procjenu njezina utjecaja na globalnoj i lokalnoj razini. Nedavno je Svjetska zdravstvena organizacija proglasila kraj pandemije, nakon čega je to učinila i Vlada Republike Hrvatske, što je ujedno i kraj istraživačkoga razdoblja za izradu ovoga rada. U radu je procijenjen utjecaj pandemije na hrvatski rudarski sektor. Uz statističke podatke o proizvodnji obrađeni su rezultati ankete gospodarskih subjekata iz područja rudarstva te su izneseni zaključci o upravljanju poduzećima u kriznim situacijama

Model of cumulative process forming and performance analysis of linear shaped explosive charges : doctoral thesis

Kumulativni eksplozivni naboji kod kojih je jedna dimenzija značajno veća od drugih nazivaju se linearni (linijski) kumulativni rezači (eng. linear shaped charge - LSC). Linearni kumulativni rezači koriste se u različitim granama industrije te se primjenjuju unutar pojedinih tehnologija: za rezanje metala, primjerice kod rušenja čeličnih konstrukcija, odvajanje iskorištenih spremnika goriva raketa, razminiranje, probijanje otvora u preprekama u vatrogastvu i slično. Budući da se kumulativni naboji koriste u rudarstvu i naftnom rudarstvu, poznavanje svojstava djelovanja i mogućnost primjene pojedinih izvedbi je od važnosti kako u razini teoretskog razmatranja djelovanja tako i u primjeni. Nastajanje kumulativnoga efekta eksplozivnih naboja proces je koji je prema fizikalnim značajkama i ponašanju materijala obloge različit u slučaju usmjeravanje energije u točku, kod kumulativnih perforatora, od usmjeravanja energije u pravac, kod linearnih rezača. Temeljitije istražen proces kumulativnih perforatora osnova je za razmatranje linearnih kumulativnih rezača koji je složeniji s obzirom na to da se materijal obloge simultano deformira i u uzdužnoj osi rezača. Ubrzavanje i deformiranje obloge kumulativnih rezača posljedica je djelovanja visokih tlakova detonacije eksplozivnog naboja i odvija se u vrlo kratkom vremenu. Prikazani rezultati mjerenja doprinose boljem razumijevanju kumulativnog procesa linijskih kumulativnih rezača i načina djelovanja linijskih kumulativnih rezača. Kvantificirani i kvalificirani su utjecajni čimbenici koji utječu na učinkovitost linijskih kumulativnih rezača. Na osnovi rezultata mjerenja određena je ovisnost utjecaja pojedinoga čimbenika na dubinu reza linijskih kumulativnih rezača. Razvijene su i validirane metode mjerenja tlaka i brzine ubrzane metalne obloge, odnosno mlaza linijskih kumulativnih rezača. Rezultati mjerenja su analizirani s obzirom na postojeće teorije i spoznaje o načinu djelovanja linijskih kumulativnih rezača. Pored toga, u radu je dan pregled drugih postupaka obrade metala energijom eksploziva.Shaped explosive charges with one dimension significantly larger than the other are called linear shaped charges. Linear shaped charges are used in various industries and they are applied within specific technologies for metal cutting, such as demolition of steel structures, separating spent rocket tanks, demining, cutting holes in the barriers for fire service, etc. Since the linear shaped charges are used in mining and petroleum engineering, understanding properties of function and applicability of different types of linear shaped charges is of great importance for theoretical analysis and for engineering application. Formation of cumulative effect of explosive charges is a process, which is different, according to the physical properties and behaviour of liner material, in the case of focusing energy to a point (conical shaped charge) and when the energy is focused to a line (linear shaped charge). More researched area of conical shaped charges is a basis for research of linear shaped charges. The cumulative effect of linear shaped charges is more complex since liner material is deformed simultaneously both in vertical and longitudinal axis of a linear shaped charge. Acceleration and deformation of liner material is caused by high pressure due to detonation and is characterized by short duration. Presented measurement results contribute to a better understanding of the cumulative effect of linear shaped charges and their function. The most important factors that affect efficiency of linear shaped charges are quantified and qualified. Correlation between particular factors and cut depth achieved by the linear shaped charges is determined according to measured results. Methods for measuring pressure and velocity of linear shaped charge jet are developed and validated. The measurement results are analysed with respect to existing theories and knowledge on the linear shaped charges. An overview of other explosive metalworking technologies is also presented in the paper

Model of cumulative process forming and performance analysis of linear shaped explosive charges : doctoral thesis

Kumulativni eksplozivni naboji kod kojih je jedna dimenzija značajno veća od drugih nazivaju se linearni (linijski) kumulativni rezači (eng. linear shaped charge - LSC). Linearni kumulativni rezači koriste se u različitim granama industrije te se primjenjuju unutar pojedinih tehnologija: za rezanje metala, primjerice kod rušenja čeličnih konstrukcija, odvajanje iskorištenih spremnika goriva raketa, razminiranje, probijanje otvora u preprekama u vatrogastvu i slično. Budući da se kumulativni naboji koriste u rudarstvu i naftnom rudarstvu, poznavanje svojstava djelovanja i mogućnost primjene pojedinih izvedbi je od važnosti kako u razini teoretskog razmatranja djelovanja tako i u primjeni. Nastajanje kumulativnoga efekta eksplozivnih naboja proces je koji je prema fizikalnim značajkama i ponašanju materijala obloge različit u slučaju usmjeravanje energije u točku, kod kumulativnih perforatora, od usmjeravanja energije u pravac, kod linearnih rezača. Temeljitije istražen proces kumulativnih perforatora osnova je za razmatranje linearnih kumulativnih rezača koji je složeniji s obzirom na to da se materijal obloge simultano deformira i u uzdužnoj osi rezača. Ubrzavanje i deformiranje obloge kumulativnih rezača posljedica je djelovanja visokih tlakova detonacije eksplozivnog naboja i odvija se u vrlo kratkom vremenu. Prikazani rezultati mjerenja doprinose boljem razumijevanju kumulativnog procesa linijskih kumulativnih rezača i načina djelovanja linijskih kumulativnih rezača. Kvantificirani i kvalificirani su utjecajni čimbenici koji utječu na učinkovitost linijskih kumulativnih rezača. Na osnovi rezultata mjerenja određena je ovisnost utjecaja pojedinoga čimbenika na dubinu reza linijskih kumulativnih rezača. Razvijene su i validirane metode mjerenja tlaka i brzine ubrzane metalne obloge, odnosno mlaza linijskih kumulativnih rezača. Rezultati mjerenja su analizirani s obzirom na postojeće teorije i spoznaje o načinu djelovanja linijskih kumulativnih rezača. Pored toga, u radu je dan pregled drugih postupaka obrade metala energijom eksploziva.Shaped explosive charges with one dimension significantly larger than the other are called linear shaped charges. Linear shaped charges are used in various industries and they are applied within specific technologies for metal cutting, such as demolition of steel structures, separating spent rocket tanks, demining, cutting holes in the barriers for fire service, etc. Since the linear shaped charges are used in mining and petroleum engineering, understanding properties of function and applicability of different types of linear shaped charges is of great importance for theoretical analysis and for engineering application. Formation of cumulative effect of explosive charges is a process, which is different, according to the physical properties and behaviour of liner material, in the case of focusing energy to a point (conical shaped charge) and when the energy is focused to a line (linear shaped charge). More researched area of conical shaped charges is a basis for research of linear shaped charges. The cumulative effect of linear shaped charges is more complex since liner material is deformed simultaneously both in vertical and longitudinal axis of a linear shaped charge. Acceleration and deformation of liner material is caused by high pressure due to detonation and is characterized by short duration. Presented measurement results contribute to a better understanding of the cumulative effect of linear shaped charges and their function. The most important factors that affect efficiency of linear shaped charges are quantified and qualified. Correlation between particular factors and cut depth achieved by the linear shaped charges is determined according to measured results. Methods for measuring pressure and velocity of linear shaped charge jet are developed and validated. The measurement results are analysed with respect to existing theories and knowledge on the linear shaped charges. An overview of other explosive metalworking technologies is also presented in the paper

Model of cumulative process forming and performance analysis of linear shaped explosive charges : doctoral thesis

Kumulativni eksplozivni naboji kod kojih je jedna dimenzija značajno veća od drugih nazivaju se linearni (linijski) kumulativni rezači (eng. linear shaped charge - LSC). Linearni kumulativni rezači koriste se u različitim granama industrije te se primjenjuju unutar pojedinih tehnologija: za rezanje metala, primjerice kod rušenja čeličnih konstrukcija, odvajanje iskorištenih spremnika goriva raketa, razminiranje, probijanje otvora u preprekama u vatrogastvu i slično. Budući da se kumulativni naboji koriste u rudarstvu i naftnom rudarstvu, poznavanje svojstava djelovanja i mogućnost primjene pojedinih izvedbi je od važnosti kako u razini teoretskog razmatranja djelovanja tako i u primjeni. Nastajanje kumulativnoga efekta eksplozivnih naboja proces je koji je prema fizikalnim značajkama i ponašanju materijala obloge različit u slučaju usmjeravanje energije u točku, kod kumulativnih perforatora, od usmjeravanja energije u pravac, kod linearnih rezača. Temeljitije istražen proces kumulativnih perforatora osnova je za razmatranje linearnih kumulativnih rezača koji je složeniji s obzirom na to da se materijal obloge simultano deformira i u uzdužnoj osi rezača. Ubrzavanje i deformiranje obloge kumulativnih rezača posljedica je djelovanja visokih tlakova detonacije eksplozivnog naboja i odvija se u vrlo kratkom vremenu. Prikazani rezultati mjerenja doprinose boljem razumijevanju kumulativnog procesa linijskih kumulativnih rezača i načina djelovanja linijskih kumulativnih rezača. Kvantificirani i kvalificirani su utjecajni čimbenici koji utječu na učinkovitost linijskih kumulativnih rezača. Na osnovi rezultata mjerenja određena je ovisnost utjecaja pojedinoga čimbenika na dubinu reza linijskih kumulativnih rezača. Razvijene su i validirane metode mjerenja tlaka i brzine ubrzane metalne obloge, odnosno mlaza linijskih kumulativnih rezača. Rezultati mjerenja su analizirani s obzirom na postojeće teorije i spoznaje o načinu djelovanja linijskih kumulativnih rezača. Pored toga, u radu je dan pregled drugih postupaka obrade metala energijom eksploziva.Shaped explosive charges with one dimension significantly larger than the other are called linear shaped charges. Linear shaped charges are used in various industries and they are applied within specific technologies for metal cutting, such as demolition of steel structures, separating spent rocket tanks, demining, cutting holes in the barriers for fire service, etc. Since the linear shaped charges are used in mining and petroleum engineering, understanding properties of function and applicability of different types of linear shaped charges is of great importance for theoretical analysis and for engineering application. Formation of cumulative effect of explosive charges is a process, which is different, according to the physical properties and behaviour of liner material, in the case of focusing energy to a point (conical shaped charge) and when the energy is focused to a line (linear shaped charge). More researched area of conical shaped charges is a basis for research of linear shaped charges. The cumulative effect of linear shaped charges is more complex since liner material is deformed simultaneously both in vertical and longitudinal axis of a linear shaped charge. Acceleration and deformation of liner material is caused by high pressure due to detonation and is characterized by short duration. Presented measurement results contribute to a better understanding of the cumulative effect of linear shaped charges and their function. The most important factors that affect efficiency of linear shaped charges are quantified and qualified. Correlation between particular factors and cut depth achieved by the linear shaped charges is determined according to measured results. Methods for measuring pressure and velocity of linear shaped charge jet are developed and validated. The measurement results are analysed with respect to existing theories and knowledge on the linear shaped charges. An overview of other explosive metalworking technologies is also presented in the paper

UČINAK MALIH RUČNO IZRAĐENIH KUMULATIVNIH NABOJA

Shaped charges are widely used in many different fields. The two main users of shaped charges are the military, where shaped charges are used as a weapon against armoured targets, and the oil industry, to perforate wells. Very often, shaped charges are the subject of scientific research focused on optimising shaped charge parameters and increasing the efficiency of shaped charges. Considering a significant number of parameters affecting the penetration depth, the optimization of shaped charge parameters is a complex process. This paper describes research on the efficiency of small handmade shaped charges. In this research, two methods are used, the first one involves simulations with numerical software and the second one is site testing. AUTODYN software was used for the numerical simulations. One of the simulations was focused on the shape and velocity of the shaped charge jet and the second on the penetration of the jet into the target material. On-site efficiency of shaped charges at different standoff distances was tested. The experimental result was compared with the AUTODYN simulation result for hand-made shaped charges placed at a distance of 90 mm from the target material. The results of the simulations agree very well with the results of the site tests. Some advantages and disadvantages of each approach are also observed.Kumulativni naboji imaju široku upotrebu u različitim područjima. Dva su glavna korisnika kumulativnih naboja: vojska, gdje se koriste kao oružje protiv oklopnih ciljeva, i naftna industrija, gdje se koriste za perforiranje bušotina. Vrlo često predmet su znanstvenih istraživanja usmjerenih na optimizaciju parametara i povećanje učinkovitosti. Uzimajući u obzir znatan broj parametara koji utječu na dubinu prodiranja, optimizacija parametara kumulativnih naboja složen je postupak. U radu su opisana istraživanja učinkovitosti malih ručno izrađenih naboja. U ovome istraživanju korištene su dvije metode, prva je simulacija u numeričkome softveru, a druga je testiranje na terenu. Za numeričku simulaciju korišten je softver AUTODYN. Jedna od simulacija bila je usmjerena na oblik i brzinu mlaza kumulativnoga naboja, a druga na prodiranje mlaza u ciljni materijal. Na terenu je ispitana učinkovitost kumulativnih naboja na različitim udaljenostima od ciljanoga materijala. Eksperimentalni rezultat uspoređen je s rezultatom AUTODYN simulacije za kumulativni naboj postavljen na udaljenosti od 90 cm od ciljanoga materijala. Rezultat simulacije vrlo se dobro slaže s rezultatom testa. Osim toga istaknute su prednosti i nedostatci pojedinoga pristupa

UTJECAJ MATERIJALA OBLOGE NA DETONACIJSKE PARAMETRE ANFO EKSPLOZIVA

Due to the low manufacturing cost and ease of handling, ammonium nitrate-fuel oil (ANFO) is one of the most popular mining explosives. ANFO explosive is a typical representative of non-ideal explosives, which means that its detonation properties are strongly dependent on the charge diameter and the existence and properties of the confinement. In this work, the effect of different confining materials on the detonation properties of ANFO explosive is studied experimentally, and by hydrocode simulation by varying charge diameter, and the type and thickness of the confining materials. The results show that, along with the diameter of the charge, density and thickness of the confining material have a key impact on the detonation properties. An empirical confinement model, applicable in the range 0.3 < mC/mE < 15, is proposed. The model enables the estimation of detonation velocity of confined ANFO charges with a mean absolute percentage error (MAPE) of 14.25%.S obzirom na dobru učinkovitost miniranja, sigurnost i cijenu, ANFO eksploziv najčešće je korišteni eksploziv za civilnu primjenu. ANFO eksploziv tipičan je predstavnik neidealnih eksploziva, što znači da njegova detonacijska svojstva jako ovise o promjeru punjenja te postojanju i svojstvima obloge. U radu se eksperimentalno i simulacijom pomoću hidrokoda proučava utjecaj različitih materijala obloge na detonacijska svojstva ANFO eksploziva mijenjanjem promjera naboja te vrste i debljine obloge. Rezultati pokazuju da uz promjer naboja ključan utjecaj na detonacijska svojstva imaju gustoća i debljina materijala obloge. Predložen je empirijski model obloge, primjenjiv u rasponu od 0,3 < mC/mE < 15. Model omogućuje procjenu brzine detonacije ANFO naboja s oblogom od različitih materijala sa srednjom apsolutnom postotnom pogreškom (MAPE) od 14,25 %

A phenomenological study of superintendents of high-performing, high-poverty school districts as servant leaders

Includes bibliographical references (pages [102]-107).This research study examines the servant-leadership characteristics expressed by public school superintendents of high-performing, high-poverty elementary school districts. The degree to which public schools and public school districts are being held accountable has increased in recent years. The No Child Left Behind Act was enacted in part to close the achievement gap between the different subgroups that are identified in the act itself. Students who are classified as low income or high poverty have consistently performed below the levels of students not classified as low income or high poverty. The superintendent, in demonstrating servant-leadership characteristics, can have a positive impact on the achievement of all students, including those from high poverty. A phenomenological study of eight public school superintendents was completed through personal interviews. The superintendents selected led kindergarten through eighth-grade public school districts with 50% or more of their students classified as low income and 60% or more of their students meeting or exceeding state standards on this midwestern state’s standardized test. Transcripts of the interviews were coded based on 15 servant-leadership characteristics. The servant-leadership characteristics, identified by Spears and Walker, were listening, empathy, healing, awareness, persuasion, conceptualization, foresight, stewardship, commitment to the growth of people building community, sense of calling, love, shared power, integrity, and serving. The study was informed by the writings of Greenleaf, Spears, DePree, Wheatley, Bennis and others. Based on the research results, servant-leadership characteristics are identified in the superintendents of this study. All of the participating superintendents expressed the servant-leadership characteristics of listening and shared power. Three of the eight superintendents expressed five or fewer servant-leadership characteristics. The manifestation of servant-leadership characteristics may contribute to highacademic achievement by students of poverty. Recommendations include further research on servant-leadership characteristics among superintendents of low-achieving schools and research on servant-leadership characteristics of superintendents of schools not considered low income. Perhaps, through comparisons and contrasts of the expressed servant-leadership characteristics, the most important attributes of servant leadership could emerge and be utilized in leadership education and training.Ed.D. (Doctor of Education

THEORIES OF ROCK BREAKAGE WITH EXPLOSIVES

Promatranje i predviđanje prirode i veličine zona oštećenja u stijenskoj masi okolnoj minskoj bušotini kao i razumijevanje mehanizama frakturiranja i drobljenja stijenske mase jedan je od najvažnijih parametara potrebnih pri projektiranju miniranja radi dobivanja željene granulacije odminirane stijenske mase i smanjenja potencijalno štetnih utjecaja miniranja na okoliš. U radu je prikazan pregled objavljenih teorija drobljenja i loma stijene detonacijom oslobođene energije eksploziva.The prediction and observation of the nature and dimensions of damaged zones in the surrounding rock mass and understanding the mechanisms of fracturing and crushing of the rock mass with explosives is one of the most important parameters in blasting design in order to obtain preferred granulation and reduce dama¬ging effects of blasting on the environment. An overview of existing rock breakage theories with the energy released by the detonation of explosives is given in this paper

The efficiency of linear shaped charges

Učinkovitost linijskih kumulativnih rezača ocjenjuje se na osnovu dubine penetracije u ciljanom materijalu. S obzirom na značajan broj parametara koji utječu na dubinu reza, optimiziranje konstrukcijskih parametara linijskih kumulativnih rezača je složen proces. Utjecaj pojedinoga parametra moguće je odrediti eksperimentalno ili teorijski predvidjeti primjenom računalnih programa, koji na temelju hidrodinamičke teorije simuliraju proces nastajanja i penetriranja mlaza linijskih kumulativnih rezača. Računalnim simulacijama moguće je predvidjeti brzinu i dubinu penetracije mlaza s određenom točnosti. Stoga su terenska mjerenja neophodna za validaciju računalne simulacije. U radu je prikazan eksperimentalni način određivanja utjecaja materijala obloge i udaljenosti rezača od mete na dubinu penetracije linijskih kumulativnih rezača. Utvrđena je ovisnost dubine penetracije o pojedinom čimbeniku te je ustanovljen međusobni odnos pojedinih čimbenika za slučaj najveće dubine penetracije.The efficiency of a linear shaped charge is estimated based on the penetration depth in a target material. Taking into consideration a significant number of parameters that affect the penetration depth, the optimization of the linear shaped charge parameters is a complex process. The effect of a certain parameter can be determined experimentally or predicted theoretically by using hydrodynamic computer programmes that simulate the formation of jet and penetration process of the linear shaped charges. The computer simulation can predict the jet velocity and penetration depth with certain accuracy. Therefore, field measurements are essential for the validation of computer simulation. This paper presents experimental determination of the effect of a mass of explosive, liner material and standoff distance on the penetration depth of the linear shaped charges. The relation between the penetration depth and various factors is established, as well as the relation between the various factors in the case of the maximum penetration depth

Personal narratives, well-being, and gender in adolescence

Relations between narratives, especially the inclusion of internal state language within narratives, and well-being have been found in adults. However, research with adolescents has been sparse and the findings inconsistent. We examined gender differences in adolescents’ personal autobiographical narratives as well as relations between internal state language and emotional well-being. Mirroring previous research with different age groups, we found that females narrate both positive and negative personal experiences in more emotional ways than do males. Also, adolescent females include more cognitive processing words indicative of self-reflection than do adolescent males. Adolescent males who told personal narratives richer in internal state language displayed higher levels of well-being, but there were no relations between internal state language in personal narratives and well-being for adolescent females. These results are interpreted in terms of gender differences in emotional processing and understanding. Directions for future research are discussed