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Эвристическая модель прогнозирования работоспособности полупроводниковых приборов
Get PDFThe threshold logic method used for electronic products when assessing their reliability in the form of predicting the performance class of products for a given operating time (K1 is a class of operable ones, K0 is a class of inoperable copies) provides for the transformation into a binary code of informative parameters obtained at the initial moment of time, and allows to build a forecasting model in the form of a table showing which code combinations correspond to the instances of the K1 class. The use of a binary transformation simplifies the forecasting procedure, but the reliability of the predictions is slightly reduced. It is relevant to obtain a forecasting model that has the simplicity of its application and provides a higher reliability of forecasting a class of products than with a binary transformation of parameters. On the example of bipolar transistors of the KT872A type, the regularities of electrical parameters used as informative ones are established, and for their transformation into a code, it is proposed to consider three areas of parameter change: the first area is the range of values between the mathematical expectations obtained separately for instances of the classes K1 and K0; the other two areas are the parameter values to the left and right of this range. Parameter values falling within the range are assigned the R code (from the word Range), outside the specified range - the code 1 (one) or 0 (zero), depending on the pattern of the informative parameter. It is explained how to convert parameters to codes 1, 0 and R and get a prediction model in the form of a logical table built from these codes. Basing on the example of the investigated transistors, it is shown that the proposed heuristic model provides the best forecasting results, practically keeping the simplicity of the basic method of threshold logic.Метод пороговой логики, применяемый для изделий электронной техники при оценке их надежности в виде прогнозирования класса работоспособности изделий для заданной наработки (K1 – класс работоспособных, K0 – класс неработоспособных экземпляров), предусматривает преобразование в двоичный код информативных параметров, полученных в начальный момент времени, и позволяет построить модель прогнозирования в виде таблицы, показывающей, каким комбинациям кода соответствуют экземпляры класса K1. Использование двоичного преобразования упрощает процедуру прогнозирования, но немного снижается достоверность прогнозов. Актуальным является получение модели прогнозирования, обладающей простотой ее применения и обеспечивающей более высокую достоверность прогнозирования класса изделий, нежели при двоичном преобразовании параметров. На примере биполярных транзисторов типа КТ872А установлены закономерности электрических параметров, используемых в качестве информативных, и для их преобразования в код предложено рассматривать три области изменения параметра: первая область – диапазон значений между математическими ожиданиями, полученными отдельно для экземпляров классов K1 и K0; две другие области – значения параметра, находящиеся слева и справа от этого диапазона. Значениям параметра, попадающим в диапазон, присваивается код R (от слова Range – диапазон), за пределами указанного диапазона – код 1 (единица) или 0 (нуль) в зависимости от закономерности информативного параметра. Поясняется, как выполнять преобразование параметров в коды 1, 0 и R и получать модель прогнозирования в виде логической таблицы, построенной из этих кодов. На примере исследуемых транзисторов показано, что предлагаемая эвристическая модель обеспечивает лучшие результаты прогнозирования, практически сохраняя простоту базового метода пороговой логики
Перестраиваемый сферотрон сантиметрового диапазона
Get PDFThe effect of the systematic component appearance (deceleration and acceleration) during asynchronous electron interaction with an inhomogeneous electromagnetic field suggests not only the academic interest [1–4] (as a new physical phenomenon), but can also have practical usage in special microwave generators of various ranges. Earlier, the following types of devices were proposed: a coaxial diode generator-diotron [5] and a spherotron based on a two-spherical resonator [6, 7]. Along with some advantages, these devices have a significant disadvantage: the frequency tuning of such generators is difficult due to the fixed resonator oscillation type by the given geometry. This article proposes and analyzes a new type of spherotron, the resonator of which consists of a coaxial line segment loaded on a two-spherical capacitor, in which the interaction between radially converging electron beams and an increasing radial electric field of the resonator run. In the coaxial line (the inductive resonator component) there is an impedance transformer (adjustable waveguide transformer with two dielectric plates) [8] consisting of movable quarter-wave washers. Their movement togather changes the resonator frequency and the mutual moving towards and away from each other is the relation with the load. The coaxial line is connected by the pin to the output waveguide. The proposed spherotron calculation showed the possibility of achieving an efficiency of up 30 % and being tuned in the given band of up 30 % with changing the accelerating voltage V0 = 1.12 V. This generator type is demanded in special (small-sized) communication systems, Doppler radar, electronic warfare with frequency tuning [9], in biochemical research and technology [10], in biological research [11], and in molecular synthesis.Эффект появления систематической составляющей (торможения и ускорения) при несинхронном взаимодействии электронов с неоднородным электромагнитным полем представляет не только академический интерес [1–4] (как новое физическое явление), но и может найти практическое использование в специальных генераторах СВЧ различных диапазонов. Ранее были предложены приборы такого типа: коаксиальный диодный генератор-диотрон [5] и сферотрон на двусферическом резонаторе [6, 7]. Наряду с некоторыми преимуществами эти приборы обладают существенным недостатком: перестройка по частоте таких генераторов затруднена из-за фиксированного заданной геометрией резонатора типа колебаний. В настоящей статье предложен и проанализирован новый тип сферотрона, резонатор которого состоит из отрезка коаксиальной линии, нагруженной на двусферическую емкость, в которой происходит взаимодействие радиально сходящихся электронных пучков с возрастающим радиальным электрическим полем резонатора. В коаксиальной линии (индуктивная составляющая резонатора) расположен трансформатор полных сопротивлений [8], состоящий из подвижных четвертьволновых шайб. Его перемещение меняет частоту резонатора, а взаимное сближение или расхождение – связь с нагрузкой. Коаксиальная линия через штырь связана с выходным волноводом. Расчет предложенного сферотрона показал возможность достижения КПД до 30 % и перестройки в полосе 30 % при изменении ускоряющего напряжения V0 = 1,12 кВ. Такой тип генератора востребован в специальных (малогабаритных) системах связи, доплеровской радиолокации, радиоэлектронной борьбы с перестройкой частоты [9], в биохимических исследованиях и технологиях [10], в биологических исследованиях [11], в молекулярном синтезе
Modeling of optical properties of hybrid metal-organic nanostructures
Get PDFTo model spectral characteristics of hybrid metal-organic nanostructures, the extended Mie theory was used, which makes it possible to calculate the extinction efficiency factor (Qext) and the scattering efficiency factor in the near zone (QNF) of two-layer spherical particles placed in an absorbing matrix. Two-layer plasmon nanospheres consisting of a metallic core (Ag, Cu) coated with dielectric shells and located into the copper phthalocyanine (CuPc) matrix were considered. The influence of dielectric shell thickness and refractive index on the characteristics of the surface plasmon resonance of absorption (SPRA) was studied. The possibility of the SPRA band tuning by changing the optical and geometrical parameters of dielectric shells was shown. It was established that dielectric shells allow to shift the surface plasmon resonance band of plasmonic nanoparticles absorption both to short- and long-wavelength spectral range depending on the relation between shell and matrix refractive indexes.To model spectral characteristics of hybrid metal-organic nanostructures, the extended Mie theory was used, which makes it possible to calculate the extinction efficiency factor (Qext) and the scattering efficiency factor in the near zone (QNF) of two-layer spherical particles placed in an absorbing matrix. Two-layer plasmon nanospheres consisting of a metallic core (Ag, Cu) coated with dielectric shells and located into the copper phthalocyanine (CuPc) matrix were considered. The influence of dielectric shell thickness and refractive index on the characteristics of the surface plasmon resonance of absorption (SPRA) was studied. The possibility of the SPRA band tuning by changing the optical and geometrical parameters of dielectric shells was shown. It was established that dielectric shells allow to shift the surface plasmon resonance band of plasmonic nanoparticles absorption both to short- and long-wavelength spectral range depending on the relation between shell and matrix refractive indexes
Использование лазерной интерферометрии для определения времени окончания плазмохимического травления слоев p-GaN и AlGaN гетероструктуры p-GaN/AlGaN/GaN с двумерным электронным газом
Get PDFRegularities of the reflected signal intensity changing in time, recorded by the detector of the laser interferometer with the operating frequency of 670 nm during the inductively coupled plasma reactive ion etching in a Cl2/N2/O2 atmosphere of GaN, p-GaN and AlGaN in AlGaN/GaN and p-GaN/AlGaN/GaN heterostructures has been established by laser interferometry and scanning electron microscopy methods due to the changes in refractive indices and etching rates. During inductively coupled plasma reactive ion etching of GaN and p-GaN layers, the intensity of the reflected signal changes according to a periodic law with the thickness change period of about 144 nm, and for AlGaN layers about 148 nm, which is due to differences in their refractive indices and etching rates. During the crossing of the p-GaN/AlGaN and AlGaN/GaN interface, there is an abrupt change in the intensity of the reflected signal within 2.7–9.5 % for 20–40 s, due to changes in the aluminum concentration, refractive indices, and etching rate at the interfaces. The change in the periodicity of the interferogram, which is accompanied by a jump in intensity when passing through the etching front through the p-GaN/AlGaN and AlGaN/GaN interface, makes it possible to determine the end time of the inductively coupled plasma reactive ion etching of the AlGaN and p-GaN layers using laser interferometry in real time in AlGaN/GaN and p-GaN/AlGaN/GaN heterostructures with two-dimensional electron gas. The obtained results can be used to form microwave and power electronics devices elements which are based on the AlGaN/GaN heterostructures.Методом лазерной интерферометрии и сканирующей электронной микроскопии установлены закономерности изменения во времени интенсивности отраженного сигнала, регистрируемого детектором лазерного интерферометра с рабочей частотой 670 нм в процессе реактивного ионного травления в индуктивно-связанной плазме в атмосфере Cl2/N2/O2 слоев GaN, p-GaN и AlGaN в гетероструктурах типов AlGaN/GaN и p-GaN/AlGaN/GaN, обусловленные изменениями их показателей преломления и скоростей травления. При реактивном ионном травлении в индуктивносвязанной плазме слоев GaN и p-GaN интенсивности отраженного сигнала изменяются по периодическому закону с периодом изменения толщины порядка 144 нм, а для слоев типа AlGaN – порядка 148 нм, что обусловлено различиями их показателей преломления и скоростей травления. При переходе границы раздела p-GaN/AlGaN и AlGaN/GaN наблюдается скачкообразное изменение интенсивности отраженного сигнала в пределах 2,7–9,5 % в течение 20–40 с, обусловленное изменениями концентрации алюминия, показателей преломления и скорости травления на границах раздела. Изменение периодичности интерферограммы, сопровождающееся скачком интенсивности при переходе фронта травления через границу раздела p-GaN/AlGaN и AlGaN/GaN, позволяет с помощью лазерной интерферометрии в реальном масштабе времени определять время окончания процесса реактивного ионного травления в индуктивно-связанной плазме слоев AlGaN и p-GaN в гетероструктурах типов AlGaN/GaN и p-GaN/AlGaN/GaN с двумерным электронным газом. Полученные результаты могут быть использованы для формирования элементов устройств СВЧ и силовой электроники на основе гетероструктур типа AlGaN/GaN
Ab initio calculations of electronic band structure of CdMnS semimagnetic semiconductors
Get PDFThis work is devoted to theoretical investigations of Cd1-xMnxS semimagnetic semiconductors (SMSC). The purpose of this work was to calculate the electronic band structure of ideal and defective Cd1- xMnxS SMSC in both antiferromagnetic (AFM) and ferromagnetic (FM) phases. Ab initio, calculations are performed in the Atomistix Toolkit (ATK) program within the Density Functional Theory (DFT) and Local Spin Density Approximation (LSDA) on Double Zeta Double Polarized (DZDP) basis. We have used Hubbard U potential UMn = 3.59 eV for 3d states for Mn atoms. Supercells of 8 and 64 atoms were constructed. After the construction of Cd1-xMnxS (x = 6.25 %; 25 %) supercells and atom relaxation and optimization of the crystal structure were carried out. Electronic band structure and density of states were calculated, the total energy has been defined in antiferromagnetic (AFM) and ferromagnetic (FM) phases. Our calculations show that the band gap increases with the increase in Mn ion concentration. It has been established that Cd or S vacancy in the crystal structure leads to the change of band gap, Fermi level shifts towards the valence or conduction band.This work is devoted to theoretical investigations of Cd1-xMnxS semimagnetic semiconductors (SMSC). The purpose of this work was to calculate the electronic band structure of ideal and defective Cd1- xMnxS SMSC in both antiferromagnetic (AFM) and ferromagnetic (FM) phases. Ab initio, calculations are performed in the Atomistix Toolkit (ATK) program within the Density Functional Theory (DFT) and Local Spin Density Approximation (LSDA) on Double Zeta Double Polarized (DZDP) basis. We have used Hubbard U potential UMn = 3.59 eV for 3d states for Mn atoms. Supercells of 8 and 64 atoms were constructed. After the construction of Cd1-xMnxS (x = 6.25 %; 25 %) supercells and atom relaxation and optimization of the crystal structure were carried out. Electronic band structure and density of states were calculated, the total energy has been defined in antiferromagnetic (AFM) and ferromagnetic (FM) phases. Our calculations show that the band gap increases with the increase in Mn ion concentration. It has been established that Cd or S vacancy in the crystal structure leads to the change of band gap, Fermi level shifts towards the valence or conduction band
First-principles study of stability and electronic properties of single-element 2D materials
Get PDFWe have estimated stability of single-element 2D materials (C2, N2, Si2, P2, Ge2, As2, Sn2, Sb2, Pb2, and Bi2) by ab initio calculations. The calculations of structural and mechanical properties of 2D materials were performed using the VASP software package. The results of calculations of stiffness tensors, Young's modulus, and Poisson's ratios show that all studied single-element 2D materials are mechanically stable. Dynamic stability was investigated by calculating the phonon dispersion of the materials using the finite displacement method. Only Pb2 has imaginary modes in the phonon dispersion curves and therefore it has dynamic unstable structure at low temperatures. The analysis of the band structures indicates the presence of insulators (N2), semiconductors (P2, As2, Bi2, Sb2), semimetals, and metals among the studied group of single-element 2D materials.We have estimated stability of single-element 2D materials (C2, N2, Si2, P2, Ge2, As2, Sn2, Sb2, Pb2, and Bi2) by ab initio calculations. The calculations of structural and mechanical properties of 2D materials were performed using the VASP software package. The results of calculations of stiffness tensors, Young's modulus, and Poisson's ratios show that all studied single-element 2D materials are mechanically stable. Dynamic stability was investigated by calculating the phonon dispersion of the materials using the finite displacement method. Only Pb2 has imaginary modes in the phonon dispersion curves and therefore it has dynamic unstable structure at low temperatures. The analysis of the band structures indicates the presence of insulators (N2), semiconductors (P2, As2, Bi2, Sb2), semimetals, and metals among the studied group of single-element 2D materials
Influence of exchange-correlation functional on the structural and electronic properties of periodic structures with transition metal atoms
Get PDFThe influence of the exchange-correlation functional on the crystal fundamental property calculation is shown. CrGeTe3, compound with transition metals, was used for the simulation of structural and electronic properties. The calculations were carried out using such functional classes as LDA and GGA. It has been shown that LDA exhibits 0.4 % and 5.2 % overestimations of the lattice constants for a and c, respectively. GGA (OR) overestimates a by 0.58 % and underestimates c by 4 %. The influence of the Hubbard correction on the band gap was also investigated. If Ueff is applied to the d-electrons, then the band gap will decrease. This is due to the hybridization of the p-electrons of the chalcogen and the d-electrons of the transition metal. Thus, GGA demonstrates better agreement with the experiment. The convergence of the calculation of the total energy with a change in the k-points and the cutoff energy were also investigated.The influence of the exchange-correlation functional on the crystal fundamental property calculation is shown. CrGeTe3, compound with transition metals, was used for the simulation of structural and electronic properties. The calculations were carried out using such functional classes as LDA and GGA. It has been shown that LDA exhibits 0.4 % and 5.2 % overestimations of the lattice constants for a and c, respectively. GGA (OR) overestimates a by 0.58 % and underestimates c by 4 %. The influence of the Hubbard correction on the band gap was also investigated. If Ueff is applied to the d-electrons, then the band gap will decrease. This is due to the hybridization of the p-electrons of the chalcogen and the d-electrons of the transition metal. Thus, GGA demonstrates better agreement with the experiment. The convergence of the calculation of the total energy with a change in the k-points and the cutoff energy were also investigated
Влияние термической нагрузки при формировании контактов Al-Al на электрические параметры интегральных микросхем с контактами алюминий-поликремний
Get PDFThis work is devoted to establishing the effect of using rapid thermal processing (RTP) method (450 °C, 7 s) to form an ohmic contact between two layers of aluminum metallization on the electrical parameters and reliability of integrated circuits. The resistance values of contact chains aluminum-silicon, aluminum-polysilicon, polysilicon-silicon n+, aluminum-silicon n+, current-voltage characteristics of the tested bipolar transistors, as well as the results of the reliability analyses by conducting thermal field tests were chosen as the analyzed parameters of this microcircuit. Comparison of these parameters was carried out with respect to the microcircuits manufactured using standard RTP method (450 °C, 20 min) to form this contact. An analysis of the results of the resistance value of various contact chains showed that, regardless of the type of thermal treatment, all contact chains, with the exception of the aluminum-polysilicon contact chain, have almost the same resistance. By analyzing the elemental composition of the cleavage in the area of this contact by scanning electron microscopy, it was found that during rapid heat treatment, the depth of penetration of aluminum into polysilicon is 2 times less than during its standard formation due to a 2-fold reduction in the time of exposure to high temperature compared to the standard process. This leads to a lower concentration of the aluminum in the silicon and as a result to a higher contact resistance between the aluminum and polysilicon. An analysis of the currentvoltage characteristics showed that they are all identical, except for the course of the direct branch of the base current value from the emitter-base voltage. The deviation of the linear nature of this dependence in the region of their low voltage values (£ 200 mV) in the case of the formation of ohmic Al-Si and Al-Al contacts with the use of long-term heat treatments is due to the predominance of the generation-recombination current in this region associated with an increased density of traps in the depleted region and on the surface of the semiconductor. The ideal behavior of the base current versus the emitter-based voltage is maintained by applying rapid RTP method to form an Al-Al contact by eliminating traps both in the depletion layer and on the surface of the semiconductor. The tests carried out on the reliability of these products showed that it does not depend on the type of formation of ohmic contacts between the metallization layers.Статья посвящена установлению влияния применения быстрой термической обработки (450 °С, 7 с) для формирования омического контакта между двумя слоями алюминиевой металлизации на электрические параметры и надежность интегральных микросхем. В качестве анализируемых параметров выбраны величины сопротивлений контактных цепочек алюминий-кремний, алюминийполикремний, поликремний-кремний n+, алюминий-кремний n+, вольт-амперные характеристики тестовых биполярных транзисторов, а также результаты анализа их надежности путем проведения термополевых испытаний. Сравнение этих параметров проводилось относительно микросхем, изготовленных с применением стандартной термообработки (450 °С, 20 мин) для формирования данного контакта. Анализ результатов величины сопротивления различных контактных цепочек показал, что независимо от вида термообработки все контактные цепочки, за исключением цепочки контактов алюминий-поликремний, имеют практически одинаковое сопротивление. Путем анализа элементного состава скола в области данного контакта методом растровой электронной микроскопии установлено, что при быстрой термической обработке глубина проникновения алюминия в поликремний в два раза меньше, чем при стандартном его формировании, за счет уменьшения в два раза времени воздействия высокой температуры. Это приводит к более низкой концентрации алюминия в кремнии и, как результат, – к более высокому контактному сопротивлению между алюминием и поликремнием. Анализ вольт-амперных характеристик показал, что все они идентичны за исключением хода прямой ветви зависимости величины базового тока от напряжения эмиттер-база. Отклонение линейного характера данной зависимости в области малых значений напряжения (£ 200 мВ) в случае формирования омических контактов Al-Si и Al-Al с применением длительных термических обработок обусловлено преобладанием в данной области генерационно-рекомбинационного тока, связанного с повышенной плотностью ловушек в обедненной области и на поверхности полупроводника. Идеальное поведение базового тока в зависимости от напряжения эмиттер-база сохраняется с применением быстрой термообработки по формированию контакта Al-Al за счет устранения ловушек как в обедненном слое, так и на поверхности полупроводника. Проведенные испытания на надежность таких изделий показали, что она не зависит от вида формирования омического контакта между слоями металлизации
Вложенное преобразование с сохранением семантики исходных данных
Get PDFIn the modern world, the data used to describe objects is often presented as sparse vectors with a large number of features. Working with them can be computationally inefficient, and often leads to overfitting; therefore, the data dimension reduction algorithms are used, one of which is auto encoders. In this article, we propose a new approach for evaluating the properties of the obtained vectors of lower dimension, as well as a loss function based on this approach. The idea of the suggested loss function is to evaluate the quality of preserving the semantic structure in the embedding space, and to add that metric to loss function to save object relations in the embedding space and thus save more useful information about objects. The results obtained show that using a combination of the mean squared loss function together with the suggested one allows to improve the quality of the embeddings.В современном мире данные, используемые для описания объектов, часто представлены в виде разряженных векторов с большим количеством признаков. Работа с такими данными является вычислительно неэффективной, что зачастую приводит к переобучению при моделировании. Поэтому используются алгоритмы понижения размерности данных, одними из которых являются автокодировщики. В статье предложен новый подход для оценки свойств полученных векторов меньшей размерности, а также основанная на этом подходе функция потерь. Идея предложенной функции потерь состоит в вычислении качества сохранения семантической структуры в пространстве вложений и добавлении этой метрики в функцию потерь, что позволяет сохранить отношения объектов в пространстве вложений и таким образом сохранить больше полезной информации об объектах. Полученные результаты показывают, что использование комбинации среднеквадратичной функции потерь вместе с предложенной позволяет улучшить качество полученных вложений
Refined Analysis of the Correlation Between the Accepted Maximum Permissible Levels of Radio Frequency Electromagnetic Fields for the Population and the Lethality Rate of Covid-19
Get PDFIn this paper, the results of a refined analysis of the correlation, previously discovered by the author, between the accepted maximum permissible levels (MPL) of radio frequency electromagnetic fields (RF EMF) for population and the mortality rate of COVID-19, carried out using the data samples from the World Health Organization (WHO), taken monthly from May 2020 to July 2021, are presented. To explain the results obtained, correlation between the accepted MPL for RF EMF, the level of vaccination of population against COVID-19, and the level of gross domestic product per capita in different countries were analyzed additionally. Analysis results confirm the presence of a noticeable correlation between the RF EMF MPLs and the COVID-19 mortality rate, especially in the first months of the analyzed period. The subsequent decrease in correlation between them by the end of analyzed period is a result of significantly larger efforts in struggle against COVID-19 in those countries where high RF EMF MPLs are adopted taking into account only the danger of thermal effects in human body, in comparison with countries where more stringent standards that take into account the danger of non-thermal bioeffects, are used. The first of these countries, having on average a higher level of economic development, ensured mass COVID-19 testing of population, imposition of tougher and longer restrictions (quarantines, lockdowns, etc.), as well as significantly higher rates of vaccination of the population. The presence of a confirmed correlation between these characteristics does not necessarily mean the existence of an unambiguous causal relationship between them. In countries of the first group with passive regulation of population protection from environmental factors, this principle is used not only in relation to RF EMF, but also in relation to the other factors. This determines the relevance of a deeper system analysis of the impact of the adopted legal systems for protecting the population from the entire set of anthropogenic factors on its health and collective immunity.In this paper, the results of a refined analysis of the correlation, previously discovered by the author, between the accepted maximum permissible levels (MPL) of radio frequency electromagnetic fields (RF EMF) for population and the mortality rate of COVID-19, carried out using the data samples from the World Health Organization (WHO), taken monthly from May 2020 to July 2021, are presented. To explain the results obtained, correlation between the accepted MPL for RF EMF, the level of vaccination of population against COVID-19, and the level of gross domestic product per capita in different countries were analyzed additionally. Analysis results confirm the presence of a noticeable correlation between the RF EMF MPLs and the COVID-19 mortality rate, especially in the first months of the analyzed period. The subsequent decrease in correlation between them by the end of analyzed period is a result of significantly larger efforts in struggle against COVID-19 in those countries where high RF EMF MPLs are adopted taking into account only the danger of thermal effects in human body, in comparison with countries where more stringent standards that take into account the danger of non-thermal bioeffects, are used. The first of these countries, having on average a higher level of economic development, ensured mass COVID-19 testing of population, imposition of tougher and longer restrictions (quarantines, lockdowns, etc.), as well as significantly higher rates of vaccination of the population. The presence of a confirmed correlation between these characteristics does not necessarily mean the existence of an unambiguous causal relationship between them. In countries of the first group with passive regulation of population protection from environmental factors, this principle is used not only in relation to RF EMF, but also in relation to the other factors. This determines the relevance of a deeper system analysis of the impact of the adopted legal systems for protecting the population from the entire set of anthropogenic factors on its health and collective immunity