bluuebunny/crossref_metadata_2025 huggingface dataset:
Static and Dynamic Properties of SPC/E Water Model
Authors: Nunia Khushi , Bayen Moushila , Ansary Sahire Azam , Kumar Anupam , Mishra Pankaj
Published: December 2023

In this work, we have studied static and dynamic properties of bulk water using SPC/E water model. We have considered 1500 water molecules confined to a three dimensional box. LAMMPS software has been used to perform molecular dynamic simulation under canonical ensemble. The partial radial distribution functions, diffusion coefficients, velocity autocorrelation functions, and mean square displacements have been calculated at 300K for different densities ranging from 900 kg/m3 to 1000 kg/m3. The principle peak heights of the partial radial distribution functions are found to decrease with increase in high density regime showing abnormal behaviour in this density regime.
A simulation study of the soft and hard radiations using jets at the LHC
Authors: Haroon R F , Roy D
Published: December 2023

In this work, different aspects of the high-energy radiation are looked at considering the LHC scenario. An event-shape variable and several jet substructure observables are studied with the Mote Carlo event simulators at the 13 TeV center of mass energy scale to mimic the current LHC environment. The event-shape and the jet substructure observables are chosen such that they are not only sensitive to the different aspects of the high energy radiation measurement but also exhibit promising features to distinguish the possible existence of new physics that considers a dark matter candidate decaying into semi-visible jet. It is verified that the observables exhibit significant sensitivities to disentangle two jets to multi-jet radiations, presence of a final state and initial state radiations, presence of a large amount of missing transverse energy as a strong indication of the possible existence of a dark matter as well as couple of promising features of a semi-visible jet are explored.
Restoration and enhancement optimization of blurred images based on SRGAN
Authors: Yuan Ziqi
Published: December 2023

Blurred images pose a significant challenge in many applications, including medical imaging, remote sensing, and surveillance systems. These images suffer from low resolution, noise, and missing data, which can hinder their interpretation and analysis. Traditional methods for image restoration and enhancement have their limitations, such as low quality and slow processing times. To overcome these challenges, this paper proposes an innovative method using Super-resolution Generative Adversarial Networks (SRGANs) to enhance image quality and fidelity. The proposed method employs adversarial training, perceptual loss, residual learning, and feature reconstruction to generate visually realistic and high-quality super-resolution (SR) images from low-resolution (LR) inputs. The SRGANs approach outperforms traditional methods, demonstrating its potential to advance image restoration and enhancement techniques. The paper also discusses possible improvements and future directions for this technique.
Identification of language from multi-lingual dataset using classification algorithms
Authors: Abinaya N , Jayadharshini P , Priyanka S , Keerthika S , Santhiya S
Published: December 2023

The process of automatically identifying the language used in a text or document is known as language identification. Language identification might represent a critical step in Natural Language Processing (NLP). It entails making an effort to foresee a text‘s natural language. Before any actions can be conducted, it is crucial to understand the language of the text. We must build a model that can anticipate the given language using the text as a guide. This provides an answer for many computational linguists and Artificial Intelligence (AI) applications. In this study, the language in the provided text was identified using machine learning algorithms and vectorization techniques. The performance of different classification algorithms like Naïve bayes, Logistic Regression, Decision Tree and Random Forest have been compared and analyzed. Vectorization technique has been done to convert the text into matrix. This paper presents the comparison of all the above algorithms performed through various measures.
Virtual human speech emotion recognition based on multi-channel CNN: MFCC, LPC, and F0 features
Authors: Ke Liwen
Published: December 2023

Convolutional neural networks (CNNs) have shown promise in virtual human speech emotion expression. Previous studies have utilized CNNs for speech emotion recognition and achieved good results. However, there are research gaps in avatar speech emotion expression, particularly concerning speaker characteristics, and limited available datasets. To address these issues, this paper collects and pre-processes speech data from multiple speakers, using features such as Mel Frequency Cepstral Coefficient (MFCC) and Linear Predictive Coding (LPC). A multi-channel CNN (MUC-CNN) model is designed to fuse different feature information and update model parameters using the Adam optimization algorithm. The model‘s performance is compared with classical methods like Support Vector Machine (SVM), Random Forest (RF), and k-Nearest Neighbors (k-NN) to determine its applicability and optimize its design and training process. Experimental evaluation shows that the MUC-CNN model outperforms classical methods in recognizing and expressing emotions in virtual human speech. By incorporating MFCC, LPC, and F0 features, the model‘s recognition capabilities are improved. The multi-channel architecture allows independent processing of each feature type, enhancing the model‘s discriminative aptitude. The performance of the model is influenced by the quantity of convolutional layers and kernels utilized. The outcomes highlight the effectiveness of the proposed MUC-CNN model for the recognition and expression of speech emotions in virtual human interactions. Future research can explore alternative feature information and refine the model architecture to further optimize performance. This technology has the potential to enhance user experience and interaction in various fields, including speech interaction, virtual reality, games, and education.
Noncommutative aspects of Villadsen algebras
Authors: Ivanescu Cristian , Kučerovský Dan
Published: December 2023

In this short article, we survey the importance of Villadsen algebras in the context of the classification theory, with an emphasis on its non-commutative aspects.
Tripled Structures of Algebroids in Gauged Double Field Theory
Authors: Mori Haruka , Sasaki Shin
Published: December 2023

Double field theory (DFT) is an effective theory of string theory. It has a manifest symmetry of T-duality. The gauge symmetry in DFT is related to some kind of algebroid structures, and they have a doubled structure. We focus on the gauge algebra of the O(D, D+n) gauged DFT and discuss an extension of the doubled structure. The gauge algebra of the O(D, D + n) gauged DFT has been described by the F-bracket. This bracket is related to some algebroid structures. We show that algebroids defined by the twisted C-bracket in the gauged DFT are built out of a direct sum of three Lie algebroids. They exhibit a “triple”, which we call the extended double, rather than a “double” structure. We also consider the geometrical realization of these structures in a (2D + n)-dimensional manifold.
Soliton solution for the integrable spin model with self-consistent potential
Authors: Sagidullayeva Zhanna
Published: December 2023

Integrable spin systems with potential are of great interest from the point of view of theoretical and applied physics. They make it possible to obtain accurate analytical solutions and study the properties of solitons - nonlinear wave structures that can be stable and move without distortion. The study of solitons in spin systems is of great importance not only for developing new methods for transmitting and processing information but also for developing spintronics and magnetoelectronics in general. These areas of technology are based on the use of the properties and control of the spin moment of electrons. Understanding and controlling spin dynamics in various systems opens up new possibilities for creating more efficient and powerful devices such as magnetic memories, spintronic transistors, and logic elements. This paper considers occurence of soliton in magnetic medium described by Generalized Landau-Lifshitz equation with self-consistent potential.
Geometrical structures of nested polyhedra
Authors: Szajewska Marzena
Published: December 2023

The polyhedra with A
3, B
3/C
3, H
3 reflection symmetry group G in the real 3D space are considered. The recursive rules for finding orbits with smaller radii, which provide the structures of nested polytopes, are demonstrated.
Magnetic monopoles in extensions of Georgi–Glashow model
Authors: Beneš Petr , Blaschke Filip
Published: December 2023

We discuss a class of effective extensions of the SU(2) Georgi–Glashow model and discuss its Bogomol’nyi–Prasad–Sommerfield (BPS) limit. We identify a specific subclass of these models that admit analytical solutions of the monopole type. We present some concrete examples and find that the resulting monopoles tend to have their energy concentrated not in their center, but rather in a spherical shell around it.
Classical and quantum gravity from the axioms of relativistic quantum mechanics
Authors: Smilga W
Published: December 2023

It is common practice to describe elementary particles by irreducible unitary representations of the Poincaré group. In the same way, multi-particle systems can be described by irreducible unitary representations of the Poincaré group. Representations of the Poincaré group are characterised by fixed eigenvalues of two Casimir operators corresponding to a fixed mass and a fixed angular momentum. In multi-particle systems (of massive spinless particles), fixing these eigenvalues leads to correlations between the particles. In the quasi-classical approximation of large quantum numbers, these correlations take on the structure of a gravitational interaction described by the field equations of conformal gravity. A theoretical value of the corresponding gravitational constant is calculated. It agrees with the empirical value used in the field equations of general relativity.
A sedenion algebraic representation of three colored fermion generations
Authors: Gresnigt Niels
Published: December 2023

Three generations of fermions with SU(3)
C
symmetry are represented algebraically in terms of the algebra of sedenions, 𝕊, generated from the octonions, 𝕆, via the Cayley-Dickson process. Despite significant recent progress in generating the Standard Model gauge groups and particle multiplets from the four normed division algebras, an algebraic motivation for the existence of exactly three generations has been difficult to substantiate. In the sedenion model, one generation of leptons and quarks with SU(3)
C
symmetry is represented in terms of two minimal left ideals of ℂℓ(6), generated from a subset of all left actions of the complex sedenions on themselves. Subsequently, the finite group S
3, which are automorphisms of 𝕊 but not of 𝕆, is used to generate two additional generations. The present paper highlight the key aspects and ideas underlying this construction.
Harmonic Oscillator with a Step and/or a Ramp
Authors: Nasuda Yuta
Published: December 2023

We discuss the one-dimensional Schrödinger equation for a harmonic oscillator with a finite step at the origin and/or an external field described by a ramp function. The first half of this paper is a partial review of our recent work. The latter half is devoted to an extension of the problem, i.e., imposing an external linear field on the negative half line. The solvability of the problem via the Hermite polynomials is discussed. We demonstrate that a harmonic oscillator with a step and a ramp can have one eigenstate whose wavefunction is expressed in terms of Hermite polynomials of different orders. Explicit examples are also provided at appropriate places in the text.
Formal developments in curved momentum space: the quantum field theory roadmap
Authors: Franchino-Viñas S A
Published: December 2023

We advocate that the dual picture of spacetime noncommutativity, i.e. the existence of a curved momentum space, could be a way out to solve some of the open conceptual problems in the field, such as the basis dependence of observables. In this framework, we show how to build deformed Klein–Gordon and Dirac equations. In addition, we give an outlook of how one could define quantum field theories, both free and interacting ones.
Exact solutions to a family of nonlinear Schrödinger equations
Authors: Vassilev Vassil M
Published: December 2023

In this article, using the method of differential constraints and Lie group analysis, new exact kink-like solutions are obtained for certain families of nonlinear Schrödinger equations with cubic-quintic nonlinearity. The foregoing solutions are presented in terms of the Lambert W function.
Classification of topological Lie quasi-bialgebra structures over the Lie algebra of Taylor series
Authors: Abedin Raschid , Maximov Stepan
Published: December 2023

In this note we present in a compact form the recently obtained classification of topological Lie quasi-bialgebra and non-degenerate Lie bialgebra structures over the Lie algebra 𝔤〚x〛, for a simple Lie algebra 𝔤.
Second order Lagrangians for (2 + 1)-dimensional generalized Boussinesq equations and an extension of the Krupka-Betounes equivalent
Authors: Palese Marcella , Zanello Fabrizio
Published: December 2023

We determine second order Lagrangians for (2 + 1)-dimensional generalized Boussinesq equations and we discuss some aspects concerning conservation laws associated with invariance properties of their extended ‘full’ equivalents, in particular of Krupka–Betounes type. Such equivalents are constructed by means of a recursive formula involving geometric integration by parts formulae.
Bond graph model study of the jet dispensing valve
Authors: Yin Jiange
Published: December 2023

The jet dispensing structure includes glue liquid delivery, mechanical drive, pneumatic drive, electromagnetic control, etc. It is a complex electromechanical hydraulic and pneumatic system. The comprehensive application of relevant professional knowledge in various fields is difficult to model and the accuracy of simulation is difficult to guarantee. This article presents the structure of valve-controlled needle jet dispensing valve which is for medium to high viscosity electronic packaging adhesives, studies the bond graph model of the jetting system with this valve as the main control object, and conducts system simulation based on a 20-sim system, laying the foundation for the research of electromechanical, hydraulic, and pneumatic multi domain coupling mathematical models.
On-line Detection of Pressure Vessel Based on Infrared Imaging Technology
Authors: Zhang Pugen
Published: December 2023

This paper introduces the application of infrared thermal imaging detection technology in the field of special pressure equipment, and applies infrared imaging detection to burners, low-temperature vessels, and tower vessels in chemical plants. The conclusion is that infrared detection technology can accurately detect temperature-maintaining defects in burners and low-temperature vessels, and can intuitively reflect the defect location in a high-heat form. For high-temperature equipment, the infrared characteristic form of insulation defects is generally displayed in an irregular chain shape, because the insulation is made up of materials that are spliced together and easily form pores at the joints. For low-temperature equipment, the humid environment caused by cold running may cause corrosion to exposed metals and even affect the process’s effectiveness. Infrared detection technology can visually reflect the location and degree of cold running, reduce equipment usage risks, and provide size and position guidance for insulation repair.
Design of Batch Automatic Testing System Based on Electric Cylinder
Authors: Yi Yu , Qu Haishan , wang Shuai , Jian Yi , Wang Huajun , Qu Ning
Published: December 2023

With the increasing demand for weapons and equipment, more manpower and material resources need to be invested to complete the batch production of weapons and equipment models. In order to save production costs and improve the efficiency of batch production, a batch automatic test system based on electric cylinders is developed. The system is divided into an automatic test system and a batch tangent system. They are respectively used to achieve product testing and batch product line change control to reduce human intervention and improve the accuracy and efficiency of product testing.
Research on low frequency noise reduction device for substation equipment
Authors: Xiao Wangqiang , Liu Qibin , Luo Bing , Xu Yongsheng , Dai Yu
Published: December 2023

Aiming at the pain point that it is difficult to control the low-frequency noise of the substation equipment, a new noise reduction method is proposed. It can reduce the noise propagation of the equipment without changing the structure of the equipment. The discrete element model of particle dampers for substation equipment is established. The energy consumption value of the particle system is used as an evaluation index. It optimizes parameters such as filling rate and particle size and determines the parameters of the scheme with the best damping effect. Through the combination of simulation and test, the test prototype was built to verify the effect. The test data showed that the total noise extremes of the first and second-floor measurement points were reduced by 14.55 dB and 6.99 dB, respectively, after installing the particle damper. This solution adds a new means of low-frequency noise control for substation equipment.
An example analysis of energy-saving improvement based on air compressor inlet pre-treatment
Authors: Cheng Fanglin , Shi Guanqu , Lu Hanyang , Gao Rongfu , Yu Shu , Song Chengqi , Zhu Jianning , Xiao Guihui , Wu Kaiqiang
Published: December 2023

Briefly introduced the basic principles and characteristics of air compressor operation, and some commonly used air compressor energy-saving operation measures in industrial enterprises; The current situation of air compressor system of Ningbo cigarette factory was analysed, and the impact of different outdoor temperature and humidity conditions on air compressor energy consumption was analysed in winter and summer. Based on the existing conditions of the factory, the fresh air intake room of the air compressor is optimized and upgraded. A double-inlet air duct system is adopted. The indoor and outdoor air enthalpy value can be automatically calculated through the temperature and humidity sensor and central control system. The air compressor intake air is pre-treated according to the results, making full use of the outdoor low enthalpy air and the existing artificial cooling source in the factory area to improve the operating efficiency of the air compressor.
Research and Analysis of Leakage Detection of Chemical Equipment Based on Infrared Technology
Authors: Zhang Pugen
Published: December 2023

This paper introduces the application of infrared thermal imaging detection technology in LDAR detection, then the various components of the chemical equipment are detected by infrared photography, and the leakage situation is analyzed. The following conclusions are drawn: The bolt preload of the flange connection is not balanced, which is easy to cause partial leakage. A large number of test data show that the larger the flange size, the greater the leakage. Because of the lack of effective non-destructive testing methods for nozzle fillet welds, infrared testing technology can be adopted for important equipment in use, which can find penetrating buried defects and reduce the risk of equipment use.
High-quality 3D Object Detection Based on Instance-aware Sampling
Authors: Zhang Xiao , Xu Bingrong , Lu Liping
Published: December 2023

Most existing 3D object detection that is researched on point clouds uses random down-sampling algorithms, which preserve the primary shape and feature information of the point clouds and extract robust features of sampling point clouds to decrease the consumption of computing resources and improve processing inference efficiency. On the other hand, this method of sampling may disregard significant areas within the point clouds, thereby diminishing the precision of detecting comparatively minute entities such as pedestrians and cyclists. In this research, an instance perception-based object detection method is presented that adaptively chooses additional foreground points in response to the properties of smaller objects in the initial point clouds. In addition, it offers end-to-end training and addresses the issue that the typical hand-designed multi-scale grouping receptive fields do not accurately reflect the size of the item. To effectively enhance the recall rate of foreground points, we present an instance-aware algorithm, which relies on farthest point sampling. Specifically, we employ dynamic gating networks to attain instance perception. This approach enables sample candidates to encompass a larger number of foreground objects. Then we use an aggregation layer to efficiently capture robust contextual features with rich spatial information. Through experiments performed on the KITTI dataset, we substantiate the effectiveness of our IAS when compared with current advanced 3D object detection methods. We have achieved a notable enhancement, especially in identifying diminutive objects.
Research on Pneumatic Test System for the Dynamic Characteristic of Hydraulic Solenoid Valve in Brake-by-Wire System
Authors: Ren Xingpeng , Lu Yi , Wang Fengming
Published: December 2023

To solve these problems caused by the use of brake fluid as a test medium in hydraulic test systems for brake-by-wire solenoid valves, such as the difficulty of cleaning the test pieces and the high corrosiveness of brake fluid, the use of clean compressed gas as a test medium was proposed. Firstly, based on the operating principle and structural parameters of a certain integrated brake-by-wire solenoid valve, a simulation model was constructed by using MATLAB/Simulink software to analyze the dynamic characteristics of the brake-by-wire solenoid valve. The eddy current was proposed as the criterion for determining the response time. Then, hydraulic and pneumatic test systems were designed. These systems allowed the dynamic characteristic of the brake-by-wire solenoid valve to be tested under hydraulic and pneumatic conditions. Finally, by adjusting the resistance parameters of the solenoid valve and using polynomial fitting, it was found that when the upper limit of qualification in the hydraulic test system was 3.50 ms, the upper limit of qualification in the pneumatic test system was 3.33 ms.
Control of Quadcopter Based on Adaptive Fast Nonsingular Terminal Sliding Mode
Authors: Wan Jinzhen , Xia Qingyuan , Shen Suiyuan
Published: December 2023

This paper presents a novel approach to address the trajectory tracking control problem for quadcopter systems subjected to multiple disturbances. The proposed method integrates sliding mode control with adaptive control techniques, resulting in an effective adaptive fast nonsingular terminal sliding mode (AFNTSM) controller. The controller structure can be divided into an internal attitude control loop and an external position control loop. In the altitude control loop, a strategy employing AFNTSM is utilized to tackle time-varying external disturbances. In the attitude control loop, given the existence of uncertain system parameters, an attitude controller is designed by combining a PID controller with an extended state observer. The asymptotic stability of the system is verified by using Lyapunov’s theorem. Finally, experimental flights validate the superiority of this control strategy over the traditional PID algorithm.
Real-time monitoring float system applied to offshore engineering
Authors: Wu Sheng , Li Lulu , Han Yunxin , Zhu Haotian , Zhang Cheng , Hu Zechen , Huang Yifeng , Jiang Nian
Published: December 2023

This paper describes a long-range, real-time monitoring and positioning float system based on STM32, which is used to monitor the position information of the equipment in marine engineering. The system adopts a solar power supply to replenish power for the system. It combines the charging control circuit and battery protection module to build a power management module to dynamically adjust the power supply strategy and the system load to realize the long-term operation of the system. Through the LoRa module, the information collected by the pressure sensor, temperature sensor, and GPS positioning module is transmitted to the remote console to realize real-time data collection, sending, and ringing. Finally, the system was tested. The experimental results show that the real-time monitoring float system solves the problem of difficult positioning of equipment and other equipment in marine engineering after falling into the sea. It reduces the difficulty of searching for marine equipment and provides more effective information for marine search and rescue.
Laves phase formation in Fe-based alloys from strengthening particle to self-healing agent: a review
Authors: Wackerling D , Rojas D , Oñate A , Castro-Cerda F M , Araya N , Sanhueza J P
Published: December 2023

In this study, were extensively reviewed the hardening and self-healing properties of Laves-phase in Fe-based alloys. First, the microstructural features of different polytypes of the Laves-phase, focusing on the thermodynamics and kinetics of formation in ferritic and martensitic steels were revised. C14 was identified as the dominant polytype in steels, providing strengthening by precipitation, anchoring of dislocation, and interphase boundaries, thereby increasing the creep resistance. Although the Laves phase is widely known as a reinforcement particle (or even a detrimental phase in some systems) in martensitic/ferritic and ferritic steels, recent findings have uncovered a promising property. Particles with self-healing characteristics provide creep resistance by delaying creep cavities formation. In this regard, different elements such as tungsten and molybdenum are known to provide this feature to binary and tertiary ferrous alloys due to their ability to diffuse into the creep cavities and form Laves-phase Fe(Mo,W)2. To date, self-healing by precipitation has only been reported in commercial stainless steel AISI 312, 347, and 304 modified with boron, nevertheless with a little contribution to creep rupture life. Although, commercial computational tools with thermodynamic and kinetic databases are available for researchers, to tackle the self-healing process with exactitude, genetic algorithms arise as a new tool for computational design. The two properties of Laves phase reported in the literature, precipitation hardening and self-healing agent, is a mix that can bring out a new research field. Therefore, it is not unreasonable to think of tailor-made high chromium creep-resistant steels reinforced by Laves-phase coupled with self-healing properties. However, owing to the characteristic of Laves-phase seems to be a complex challenge, mainly due to the crystallographic features of this phase in comparison with the host matrix, available computational tools, and databases.
Simultaneous adsorption of malachite green, methyl orange, and rhodamine B with TiO2/macadamia nutshells-derived activated carbon composite
Authors: Thuy Le Thi Thanh , Thi Thuy Pham , Thi Giang Anh Pham , Tien Nguyen Anh , Thi Hong Bich Nguyen , Khieu Dinh Quang
Published: December 2023

In this study, TiO2/activated carbon (TiO2/MAC) composite was synthesized from activated carbon prepared from macadamia nutshells and a water-soluble titanium complex, and it was used to simultaneously adsorb malachite green (MG), methyl orange (MO), and rhodamine B (RhB) from aqueous solutions. The kinetic studies show that the pseudo-second-order kinetic model describes the adsorption experimental data the best. The equilibrium data of the trinary system were analyzed via the ideal adsorption solution theory (IAST) and the Langmuir and P-factor-Langmuir extended models that combine the three single-component isotherms (Langmuir, Freundlich, and Sips). The AICs (Akaike Information Criterion) values indicate that IAST incorporating the Langmuir model is the most suitable to describe the removal of the dyes in the trinary solution. The TiO2/MAC composite exhibits a high dye adsorption capacity compared with those of the published adsorbents. The thermodynamic analysis reveals that the adsorption is spontaneous and endothermic. The high adsorption capacity and the recyclability through photocatalytic self-cleaning show that TiO2/MAC can be utilized as a sustainable alternative for the simultaneous elimination of textile dyes from effluents.
How to avoid solidification cracking in arc welding of aluminum alloys: a review on weld metal grain refinement approaches
Authors: Yolcu Coşkun , Kahraman Fatih
Published: December 2023

Joining aluminum alloys with arc welding methods is frequently subject to literature and industrial applications. Although aluminum alloys have different difficulties in the arc welded process, the formation and elimination of solidification cracking defects is a more complex phenomenon. Since avoidance of this defect requires specific approaches and methods, special attempts and improvements have been studied frequently on this subject in recent years. Studies in the literature have clearly shown that this defect, which is often encountered in aluminum alloys, takes place along the grain boundaries. Therefore, the major approach to eliminate this defect is activating nucleation and decreasing the grain size. In this context, modification approaches in the literature, which are frequently used for arc welding of aluminum alloys, have been developed to use three different mechanisms including heterogeneous nucleation, dendrite fragmentation, and grain detachment. While it is aimed to increase heterogeneous nucleation by reinforcing filler metals with compounds in the inoculation approach; dendrite fragmentation and grain detachment are also aimed in the approaches where external effects and forces are used. Within the frame of references, it is also possible to review the external factors aiming to improve weld pool convection and thermal conditions under two headings, which are weld pool stirring and pulsed arc current approaches. The weld pool stirring approach also includes ultrasonic treatment and magnetic arc oscillation methods. In this study, solidification cracking defect that frequently occurs in the arc welding of aluminum alloys is explained fundamentally and the attempts to eliminate this defect are presented as a review paper in a comprehensive manner.
Optimal conversion coefficient from easily measurable dose to effective dose with consideration to radiation quality for posterior–anterior chest radiography
Authors: Ono Koji , Asada Yasuki
Published: December 2023

Effective dose is sometimes used to compare medical radiation exposure to patients and natural radiation for providing explanations about radiation exposure to patients, but its calculation is lengthy and requires dedicated measuring devices. The purpose of this study was to identify the most suitable conversion coefficient for conversion of easily measurable dose to effective dose in posterior–anterior chest radiography, and to evaluate its accuracy by direct measurement. We constructed an examination environment using Monte Carlo simulation, and evaluated the variation in conversion coefficients from incident air kerma (IAK), entrance-surface air kerma (ESAK), and air kerma-area product (KAP) to effective dose when the irradiation field size and radiation quality were changed. Effective doses were also measured directly using thermoluminescence dosimeters and compared with the effective dose obtained from conversion coefficients. The KAP conversion coefficient most effectively suppressed the effect of irradiation field size, and was then used to set conversion coefficients for various half-value layers. The optimal conversion coefficient was 0.00023 [mSv/(mGy·cm2)] at 120 kVp (half-value layer = 5.5 mmAl). Evaluation of the direct measurements obtained with various radiation qualities revealed that the accuracy of the conversion coefficient was maintained at ≤ 11%. The proposed conversion coefficient can be easily calculated even in facilities that do not have equipment for measuring effective dose, and might enable the use of effective dose for providing explanations about radiation exposure to patients.
The Petrostate in Africa
Authors: Adunbi Omolade
Published: December 2023

Oil exploration in Africa began during the colonial period. The discovery of oil in many African states and its attendant promises of development has been a double-edged sword for the continent.In many African countries, discovery of abundant oil fields coincided with independence, entrusting the management of huge oil reserves to the postcolonial states that emerged from the rubble of colonialism. Oil has made Africa a strategic energy source for the rest of the world. As of 2017, Africa was estimated to contain upward of 126 billion barrels of proven oil reserves, constituting about 10 percent of world reserves. Yet the search for more oil continues in many African countries. Oil generates immense revenue for states that have it but it also makes them susceptible to a boom-and-bust cycle that mono-economies often confront. The finite nature of oil and the technology that is needed to extract it have made oil a beautiful bride for multinational corporations and the state which partners with them. Elite competition is often the norm in states rich in oil, where its control is often accompanied by access to the huge resources, with no benefits accruing to the larger population. The process of elite accumulation of oil rent has preoccupied most scholarship on Africa since the 1970s, when many oil-rich states experienced a boom—hence the notion that such countries on the continent are a petrostate. Petrostates are susceptible to the resource curse of mono-economies, according to the analyses that have dominated the political economy literature for the better part of the last half century.
Meroe and Aksum
Authors: Beldados Alemseged
Published: December 2023

Within the tropics of Africa, the oldest identified cities and states are located along the Middle Nile in Nubia. One of the best documented of these cities and states is Meroe. It is situated about 124 miles (200 km) northeast of Khartoum. The city of Meroe was mentioned by Herodotus as far back as the 5th century bce. According to Herodotus, Meroe was the major city of the Ethiopians/formerly also known as abyssinia. In the 21st century, the site of Meroe is the largest archaeological site in Sudan. As an archaeological site, the structures cover an area of about half a mile (0.8 km). The Meroitic state was in power for almost 600 years (between 250 bce and 350 ce). Within this period, fifty-seven kings and queens were recorded to have ruled the empire. Women had political influence as leaders during the height of Meroitic power.

The Aksumite civilization flourished during the first half of the 1st century ce in the valley of west-central Tigray between the Beta Giyorgis and Mai Qoho plateaus. It lasted until the 7th century ce. Most of the data about the cultivation of crops during the Aksumite period have been acquired from archaeological studies of soil samples from various contexts of excavations. Animal remains have also been well studied. Observations of the remaining structures and buildings that are still erect have enabled an understanding of the raw materials used in Aksumite architecture. In almost all cases, the raw materials used were stones with additions of wooden parts.

The presence of long-standing contact between Meroe and Aksum can be reconstructed through archaeological and architectural material culture remains recovered on both sides.
Eduardo Mondlane
Authors: Sansone Livio
Published: December 2023

Eduardo Chivambo Mondlane (1920–1969) was one of the founders of the Mozambique Liberation Front (Frelimo) and its first president until his assassination. Generally considered one the “fathers” of independent Mozambique and the unifier of this young country, in recognition of that and his academic standing—he had a PhD in sociology—the main university of Mozambique is named after him. His singular, exciting, cosmopolitan, and engaged life has thus far attracted less international attention than could be expected, even though, over the last decade, also on account of his centennial in 2020, a growing national and international scholarship is developing around several facets of Mondlane’s biography. One aspect that is still relatively unexplored is his academic training and many years spent abroad studying in South Africa, Portugal, and the United States. His international training and showing how this had a profound impact on his performance as leader of Frelimo.
Women and Mining in Africa
Authors: Rutherford Blair , Buss Doris
Published: December 2023

Women have long participated in mining in Africa and have been implicated in it in varied ways. The combination of archaeological research, oral histories, comparisons with colonial and postcolonial mining activities, and a few written observations show that African women were active in various mining activities throughout the continent before Europeans began their formal colonization of much of the continent. Conquest by different European states and colonial rule brought not only a new type of mining and new players, networks, and markets into many parts of Africa but also new gendered norms and discourses when it came to women working in mines. Colonial legislation often prohibited women from working underground, and women’s work in mines was actively discouraged or hidden. European-controlled industrial mining in Africa in the late 19th century up until the 1970s was labor intensive, almost exclusively hiring men, most of whom were African. Yet these industrial mining areas attracted many women for economic and social reasons. These women became the targets of varied types of moral projects from different colonial and African authorities, which strongly shaped the pathways, possibilities, and barriers to varied (non-mining) economic activities for African women in the mining communities. The end of colonial rule and the emerging independent governments across Africa starting in the 1950s saw significant changes for women and mining in different parts of the continent, even though there are many strong continuities from the colonial period. These continuities and changes are apparent when examining access to mining livelihoods and working conditions for women and the role of family dynamics, both in terms of industrial mining and artisanal and small-scale mining. There is also a growing targeting of women and mining in Africa in policies, programs, and by social movements.
History of the Mount Kilimanjaro Area
Authors: Bender Matthew V.
Published: December 2023

Mount Kilimanjaro is perhaps the most recognized geographic feature in sub-Saharan Africa. Rising to a height of 5,895 meters (19,340 feet), it is the tallest peak in Africa, the world’s tallest freestanding mountain, and the highest volcano outside of South America. The massif extends 95 kilometers from east to west and 65 kilometers north to south and is at least 30 kilometers away from the nearest peaks. Owing to its tremendous size, it gives rise to five distinct climate zones—temperate forest, rainforest, moorland, alpine desert, and ice cap—that emerge from the surrounding arid Maasai steppe. Its numerous rivers, arising in rainforest, provide surface water resources to the lower slopes as well as the surrounding watershed, which extends more than 300 kilometers to the Indian Ocean. Kilimanjaro is perhaps best known for its white cap, consisting of both glaciers and seasonal snowfall, that makes it unique among mountains in Africa.

As an island in the middle of the steppe, Kilimanjaro has long been important in the lives of African communities. It has been most important to the Chagga-speaking peoples who have made it their permanent home. For more than five hundred years, they have developed agricultural societies on the southern and eastern slopes of the mountain, featuring intensive agriculture of bananas, yams, and other crops as well as an extensive system of surface irrigation. The mountain has also long been a spectacle for outsiders. In the mid-19th century, Europeans became enamored with the snow-capped mountain in Africa. A flood of explorers, missionaries, and mountaineers gave way to European conquest and colonization that lasted from the 1880s to the 1960s. Colonialism not only transformed life for Chagga peoples but also made Kilimanjaro into a symbol with broad-reaching importance across the continent and beyond.

For more than a century, the Kilimanjaro area has been the focal point of contestation, debate, and struggle that, in many ways, makes it a microcosm of the colonial and postcolonial experiences of Africa as a whole. Colonialism introduced new political, economic, social, and religious structures, embedded in a context of coercion and violence, that not only generated debate and resistance but also opened new opportunities for some. These dynamics have remained to a large extent in the postcolonial period, as outside actors ranging from the Tanzanian government and nongovernmental organizations to the International Monetary Fund and climate scientists have attempted to control and harness the mountain’s resources, often at the expense of local interests. Yet for the Chagga, the mountain very much remains their home, and they vehemently defend their right to control its valuable resources. As the threat of climate change looms, these clashes between local and outside interests will likely become even more fervent.
Happiness and Productivity in the Workplace
Authors: Nazneen Mahnaz , Sgroi Daniel
Published: December 2023

Happiness has become an important concept in economics as a target for government policy at the national level. This is mirrored in an increasing understanding of the microeconomic effects of increased happiness. While correlational studies have for many years documented a relationship between individual-level happiness and productivity, more recent work provides causal evidence that a positive shock to happiness can boost productivity significantly. These studies include three strands of research. The first provides a number of longitudinal surveys that have generated evidence linking happiness to productivity but run the risk of confounding happiness with other related variables that may be driving the relationship. The second includes laboratory experiments that simulate a workplace under tightly controlled conditions, and this strand has established a clear relationship between positive happiness shocks and rises in productivity. The third involves examining experimental field data, which sacrifices the control of laboratory experiments but offers greater realism. However, there is still work to be done generalizing these findings to more complex work environments, especially those that involve cooperative and team-based tasks where increases in happiness may have other consequences.
Mining and the Environment
Authors: Vrtis George , Elsass Kirke
Published: December 2023

Human societies have always depended upon minerals. Even a cursory glance at any world history textbook reveals the centrality of minerals—and thus mining—in forging human cultures in antiquity. The stone age, the bronze age, the iron age—each of these complex periods are, in part, defined by the increasing human engagement with the minerals used to characterize them. In the history of the United States, mineral extraction has also been fundamental to the nature and evolution of the nation, as well as its colonial and Indigenous pasts. It was present in Native American societies prior to European contact, accelerated with European colonization, became foundational with the advent of the industrial revolution, was renegotiated with the rise of the environmental movement, and has influenced the United States’ relationship with many parts of the world. As these developments have unfolded, mining and mineral use have radically altered the natural world and profoundly shaped people’s relationships with the environment and with one another.
Contemporary Visual Art and Religion
Authors: Colonna Dominic
Published: December 2023

Contemporary visual art that uses themes and symbols of particular religious traditions has the potential to alienate both those who are adherents of those traditions and those who are non-adherents. Such art is often characterized as sentimental, superstitious, naïve, exclusivist, or triumphalist by modern standards of judgment. At the same time, efforts to avoid exclusivism or triumphalism in contemporary visual art can render the meanings of works so vague that it is hard to identify a work with any particular religion. For these reasons and more, the art world tends to disparage the benign use of religious themes and symbols in art and tends to accept works that are transgressive—that is, art that transgresses the boundaries of religious decorum.

Material and visual culture studies provide ways for the art world to find value in and analyze the use of religious themes and symbols in contemporary visual art. These approaches have widened the scope of works that might be identified as contemporary visual art: popular, mass-produced, and folk art are all within the purview of analyses of contemporary visual art. These studies examine how religious themes and symbols function in religious communities and in the wider communities of which they are a part. Even when studying the function of visual and material culture within a particular religious tradition, these studies tend to identify common or essential themes in different religions. The contemporary preference for being “spiritual but not religious” emerges in the identification of common religious themes and symbols.

Contemporary theological approaches to the study and appreciation of contemporary visual art are “insider” methods that religious adherents use to assess critically the value of the use of religious themes and symbols in modern culture. These insider methods identify orthodox uses of religious themes and symbols in contemporary visual art, not only to identify negatively that which is unorthodox or heterodox, but also to identify works of art that celebrate religious beliefs, make traditional beliefs relevant, and help to shape new ways of engaging the wider community. Theological methods often incorporate the work of material and visual studies scholars. Like these scholars, theologians seek to affirm the value of unique religious beliefs in an increasingly pluralistic world.