Paper Research Articles

User-driven instructions reduce errors in child restraint use: a randomised controlled trial in Sydney, Australia

Background and objectivesCrash injury risk is reduced when a child correctly uses an appropriate restraint; however, incorrect restraint use remains widespread. The aim of this study was to determine whether...

TOMBSTONE OF PRINCE DMYTRO KOZEKA: A «NEW AND OLD» LAPIDARY MONUMENT OF VOLYN OF THE 16th CENTURY

The Scientific Archive of the Institute of Archaeology of the National Academy of Sciences of Ukraine holds a drawing of the tombstone of Prince Dmytro Kozeka. The drawing on a sheet of paper was made in pencil in the late nineteenth and early twentieth centuries. It contains two inscriptions (epitaphs) in Old Ukrainian and Latin and the princely coat of arms between them. The texts of the inscriptions were published twice in the nineteenth century. The large coat of arms on the tombstone has never been described. Its image, as well as the image of the inscriptions, is published for the first time. The large coat of arms has the shape of a heraldic shield inscribed in a circle. The shape of the shield is made in the Baroque style. Four heraldic signs are symmetrically arranged on the shield, the first of which, in the form of a bow and cross, is the minor coat of arms of the prince. This sign is present on the personal seals of Dmytro Kozeka. The second sign is still unknown in the heraldry of Ukraine in the sixteenth century. Two other signs belong to well-known arms used by many noble families. The paper is accompanied by illustrations that show a complete drawing of the prince’s tombstone and individual elements of this lapidary monument: two epitaphs and a great coat of arms, opening the way for studying the vocabulary of the inscriptions and performing paleographic analysis. The attribution of the coat of arms will allow us to clarify the genealogy of the Kozeka family. Prince Dmytro Kozeka died in 1583 and was buried in the Church of the Assumption of Our Lady in the monastery not far from Zymne village near Volodymyr city. The marble slab on the grave was installed by his wife Kateryna Falchevska. After the turn of the nineteenth and twentieth centuries, there is no evidence of the location of the slab. The Kozeka family appeared in Volhynia in the mid-fifteenth century. Their origin is not clear. Dmytro Kozeka is the most famous representative of this family, according to written sources. The paper describes some episodes of his biography, gives an overview of the princely estates, specifies the time period when his father died, and reveals the previously unknown names of his two sisters. The tombstone of Prince Dmytro Kozeka is a valuable historical source for the study of the elite stratum of the Ukrainian population of the early modern period.

Analytical Spectral Semi-quantitative Dating Method of Printed Text Toner Using Raman Spectroscopy and the Fluorescence signal of Paper Sheet Cellulose

Abstract: The chemical processes that occur during the surface degradation of document paper under the influence of external factors were studied by Raman spectroscopy. The possibility of comparing the same processes occurring on clean free paper and under printed text toner letters is of interest. It is assumed that the transformation of cellulose can occur at different rates in the areas of paper exposed to direct atmospheric and light exposure and in the areas containing an intermediate layer of the toner. The most stable temporal changes occur in the region of C–C–C and C– C–O vibrations of glycosidic rings in the short-wavelength region of the Raman spectrum. Background: The main areas of research in the field of document dating, mainly focused on chromatographic methods. These methods are based on studying the dynamics of evaporation of volatile ink components. There is also a variety of chromatography techniques, including gas chromatography, ion chromatography, high performance liquid chromatography, thin layer chromatography and gas chromatography-mass spectrometry. This indicates the wide range of approaches and techniques used to determine the age of written materials. However, all these methods are used mainly during the first two years after writing the document details, which does not allow examining documents that are more than two years old. Methods: Raman spectroscopy was used as the main research method. The object of the study was sheets of white A4 paper with printed text printed on them, produced on a laser printer. The subject of the study was areas of paper free of text, as well as areas of paper under toner. The integrated fluorescence of a paper optical brightener based on stilbene was studied in the wavelength range of 400–500 nm. Also, all objects were studied using optical microscopy. Results: The comparison of peak intensity values averaged over 10 brands over the years made it possible to reveal the following regularities: – the ratio of peaks in the paper spectra from which the toner was removed is greater than in the blank paper spectra, and the difference becomes less noticeable as the age of the paper decreases. The ratio of the intensity of the 330 cm-1 peak to the intensity of the 1603 cm-1 peak: the older the document becomes, the lower the average ratios of these peaks in both the blank paper spectra and in the spectra of paper from which the toner has been removed. –the intensity of the peak in the region of 280 cm-1 and 1 086 cm-1 of the Raman shift increases with decreasing the age of the toner-free paper.– a gradual increase in the intensity of the 380 cm-1 peak is observed when comparing the paper samples from which the toner was removed for 2016, 2018, 2020, and 2022. Regularity was also found in the change in the ratio of the average statistical values of the peak at 280 cm-1 in the spectra of the paper under the toner to a similar peak in the spectra of the paper free from text: the value of this ratio decreases with decreasing the paper age. At the same time, the paper fluorescence signal is an informative parameter that makes it possible to establish some facts from the document’s history. With artificial document aging, a significant broadening of the dispersion region and the appearance of its “splitting” into two or three strata are observed in the distribution of the fluorescence signal level of a paper sheet relative to the average value. The average fluorescence signal of a naturally aged sheet decreases with the age of the document. Conclusion: As a result of research, it has been established that Raman spectroscopy can be successfully used as a method for dating documents. When comparing the degree of degradation of the surface of open areas of paper and areas protected by toner of printed text, different effects of external factors on these areas were established, leading to different rates of degradation processes. The use of Raman peak intensity ratios for paper components in exposed areas compared to peaks under printed text further expands the methodology. The emphasis on spectral methods, in particular fluorescence signal distribution and Raman spectroscopy, to detect surface changes is well justified. It demonstrates a holistic approach to document analysis, taking into account both the chemical changes observed using Raman spectroscopy and the fluorescence signal distribution that may indicate signs of artificial aging through light exposure. This combination of methods appears to be reliable for assessing the age of documents and can make significant contributions to the field of forensic document examination.

Cutting edge document examination: The physical fit of machine-cut edges of paper.

This technical note describes in detail a method for associating individual sheets of blank A4 white paper from the same ream by the physical fit of machine-cut edges. A large-scale laboratory trial involving ~700 sheets of paper from 24 different reams (plus one spoiled sample), and more than 20,000 potential physical fits, correctly associated and sequenced 219 pairs of sheets together with a 100% empirical success rate and no false associations. The edge profile of each short machine-cut end of a sheet of A4 paper allows us to physically fit sheets of paper from the same ream to each other and use this to predict the sequence of sheets in a set of documents. In a real-life scenario, it may now be possible to detect the substitution or addition of a sheet in a multipage document, link documents from different sources to each other or to a common source of paper (e.g. to paper from a seized printer or from an accused's address) or to date documents. The study provides data for the application of this method in forensic casework and supports the practitioner when forming conclusions in this type of case.

The Influence of Some Environmental Factors on Temporary Degradation of Organic Components of Paper Pulp and Writing Compositions

Abstract: Paper sheet materials and written compositions are complex multi-component mixtures, including dyes, solvents and resins, preservatives, and antioxidants, i.e., complex organic mixtures that change over time. Technical examination of materials and documents is in demand in the judicial and archival industry. Determining the actual date of appearance of a particular inscription on a sheet of paper is one of the most important and complex expert tasks. The task is divided into two components: analysis of the processes of temporary degradation of paper pulp and processes of temporary degradation of organic writing materials.

Innovative Ag@Cu/white sand and polysaccharide based nanocomposites: A simple route to conductive and antibacterial paper coatings

In this work, we presented a simple method for preparing nanocomposite pigments via doping the naturally occurring white sand pigment using silver (Ag) and copper (Cu). The nanocomposites (Ag@WS, Cu@WS, and Ag&Cu@WS) were produced in two suspensions at 25 % and 50 % w/v concentrations, utilizing casein (Cas) and nanostarch (NanoSt) as bio-friendly binders. The prepared nanocomposite pigments were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction crystallography (XRD), and dynamic light scattering (DLS), as well as topographical analysis including scanning electron microscopy (SEM), EDX, and transmission electron microscopy (TEM). The coated paper sheets were characterized using topographical analysis and mechanical, optical, physical, and electrical properties. The antimicrobial activity assay was carried out on the coated paper sheets using the most infectious microbial pathogens. FTIR and XRD analyses confirmed the presence of Cas and NanoSt in the samples. The addition of white sand (WS) and doped nano-metals influenced the crystallographic structure of the polysaccharides. A small amount of Ag, Cu, and Ag&Cu nanoparticles was investigated through EDX. The white sand was a plate structure decorated with spherical Ag, Cu, and Ag&Cu nanoparticles, with an average size of about 147, 105, and 78 nm, as observed from TEM images and DLS. The antimicrobial activity assays revealed that nanocomposite pigment embedded with bimetallic Ag&Cu nanoparticles exhibited a synergistic effect, resulting in enhanced broad-spectrum antibacterial and antifungal activities. The electrical performance of the coated paper was enhanced by using Ag&Cu@WS nanocomposite pigment. Incorporating 50 % Cu@WS into the coating resulted in significant improvements in the mechanical properties of the paper. Specifically, tensile strength increased by 6.3 N/mm, tensile index by 69.06 N m/g, stretching by 1.68 %, tensile energy absorption by 71.4 J/m2, burst strength by 257.75 kPa, and burst index by 2.83 kPa m2/g. Furthermore, incorporating 50 % Ag&Cu@WS increased the opacity to 93.2 % and reduced the roughness of the coated paper by 36 % compared to using 50 % Ag@WS or 50 % Cu@WS alone.

Can 5 Minutes of Finger Actions Boost Creative Incubation?

AbstractPrevious studies suggest that the activation of the motor system – either via action, motor imagery, or brain stimulation – may increase subsequent performance on divergent thinking tasks (e.g., the alternate uses task; AUT). We tested this idea in a within-subjects design by administering the AUT using four different target objects and four different 5-min incubation tasks that differed in terms of arm and finger movements. In between-subjects designs, 0-back incubation has been shown to yield more creative responses than rest. Additionally, we included two new incubations that both involved arm actions, but differed in the amount of finger actions (Iranian dance, ballet dance). Incubation tasks involving finger actions (Iranian dance, 0-back) were predicted to increase creativity for objects that are typically manipulated with the fingers. There was a main effect of object. Alternate uses given to the paperclip were rated as more creative than those given to the other objects. With our within-subjects design, we could not replicate the previously described difference between 0-back and rest incubations. However, hypothesis-driven comparisons showed that, although the interaction of object and incubation was not significant, Iranian dance yielded more creative usages for paperclip than for sheet of paper, cup and brick, and all other incubations yielded more creative usages for paperclip than for brick. Iranian dance also generated marginally more creative usages than ballet. Our results suggest that if the hypothesized effects exist, they are likely to be small. Overall, AUT performance seems more influenced by the AUT object than by type of incubation.

Pore-Fiber Transport Dynamics of Aqueous Cosolvent Solutions in Paper.

After inkjet printing onto uncoated and unsized paper, the ink is first imbibed into the interfiber pores and subsequently absorbed by the cellulose fibers. The achievable print quality depends on the rate of this pore-fiber transport. The latter is accompanied by mechanical expansion of the fibers and the paper sheet. Therefore, we systematically monitored the swelling dynamics of several paper types as a function of ink composition by means of four different measurement techniques. Using aqueous cosolvent solutions as model inks, we found an approximately exponential relation of the time scales of pore-fiber transport with the cosolvent concentration and an approximately linear relation with its molecular weight. Addition of surfactants can substantially speed-up pore-fiber transport.

4D printing of the ferrite permanent magnet BaFe12O19 and its intelligent shape memory effect

4D printing of the barium ferrite permanent magnets provides new opportunities for intelligent structure and process innovation of permanent magnets. In this paper, the preparation, filament manufacture, and intelligent printing methods with shape memory/recovery effect are studied for the barium ferrite permanent magnet. Firstly, the PLA/TPU/BaFe12O19 composite materials are developed by adding different contents of ferrite permanent magnet BaFe12O19 powders into the PLA/TPU (polylactic acid/thermoplastic polyurethane) matrix. The weight percentage of the BaFe12O19 is 10–40 wt% with an interval of 10 wt%. Secondly, the composites are pelletized and further extruded to manufacture composite filaments with different BaFe12O19 contents. Scanning electron microscope (SEM) is used for the microstructural analysis. The BaFe12O19 particles are uniformly distributed in the PLA/TPU matrix, and the slight particle agglomeration phenomenon occurs in the composite filaments with 30 and 40 wt% BaFe12O19. The thermal properties of PLA/TPU/BaFe12O19 composite filaments are analyzed by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). After adding the barium ferrite particles, the glass transition temperature of the composite filaments changes within a small range from 53.5 °C to 55 °C. Thirdly, the filaments are successfully manufactured to magnet parts by the fused deposition modeling (FDM) 3D printing for the tests of mechanical, magnetic, and shape recovery properties. With the increase of the barium ferrite content, the magnetic properties show a rising trend, proving the feasibility of using 3D printing technology to make magnets. The shape memory effects of the printed parts are excellent and the shape recovery ratios show a rising trend, from 85.6 % to 88.9 % under heat contact stimulus and from 88.9 % to 97.8 % under electromagnetic induction non-contact stimulus. Relatively, the parts hold fast response speed due to direct contact with the heat source under the heat stimulus, and the parts hold higher shape recovery ratios due to more heats produced under the electromagnetic induction stimulus. The addition of magnetic particles is helpful to improve the heat transfer ability and provide the possibility of non-contact heat transfer. The magnetic parts with complex structure and intelligent shape memory/recovery effect can be achieved for special application requirements. As a result, the research of this paper expands preparation methods of new magnetic composite materials, explores the manufacture process for intelligent magnets and lays a solid foundation for the development of new permanent magnet devices.

Nyitottság, elhivatottság, patriotizmus. Beszélgetés Szilágyi Istvánnal [Interjú] = Openness, Commitment, Patriotism: Conversation with István Szilágyi [Interview

This interview presents Professor István Szilágyi’s life and the major events in his career. It includes, among other things, the early school and university years, as well as all those by whom his career has been shaped. The semi-structured interview discusses his research activities, his travels and his advice for the younger generation of geographers. Professor István Szilágyi is a retired professor at the University of Pécs and the former Dean of the Faculty of Modern Philology and Social Sciences at Pannon University. He is a renowned researcher in the theory of international relations, geopolitics and political changes in Latin America and the Hispanic world. The Professor has not only published more than hundreds of papers and book chapters in Hungarian, English, German, Russian, Portuguese and Spanish, but also, he is the author of seventeen monographs. Throughout his career, he has developed significant foreign contacts in Latin America and Europe. As a guest professor, he has visited Valladolid, Paris, Cluj-Napoca, Cadiz, Valencia, La Laguna and Dijon, among others. He has also carried out research in Portugal, Brazil, Chile, Russia and Cuba.

Antioxidant and antimicrobial emulsions with amphiphilic olive extract, nanocellulose-stabilized thyme oil and common salts for active paper-based packaging

Anionic cellulose nanofibers (CNFs) were used to stabilize emulsions that combined water-soluble (and oil-soluble), strongly antioxidant extracts with a water-immiscible, notably antimicrobial essential oil. Specifically, the radical scavenging activity was primarily provided by aqueous extracts from olive fruit (Olea europaea L.), while the antimicrobial effects owed eminently to thyme oil (Thymus vulgaris L.). The resulting emulsions were highly viscous at low shear rate (4.4 Pa·s) and displayed yield stress. The addition of edible salts decreased the yield stress, the apparent viscosity and the droplet size, to the detriment of stability at ionic strengths above 50 mM. Once characterized, the antioxidant and antimicrobial emulsions were applied on packaging-grade paper. Coated paper sheets inhibited the growth of Listeria monocytogenes, a common foodborne pathogen, and acted as antioxidant emitters. In this sense, the release to food simulants A (ethanol 10 vol%), B (acetic acid 3 wt%), and C (ethanol 20 vol%) was assessed. A 24-hour exposure of 0.01 m2 of coated paper to 0.1 L of these hydrophilic simulants achieved inhibition levels of the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) in the 15–29 % range. All considered, the bioactive properties of thyme essential oil towards lipophilic food products can be complemented with the antioxidant activity of aqueous olive extracts towards hydrophilic systems, resulting in a versatile combination for active food packaging.

Development and evaluation of hinokitiol active paper sheets for the postharvest management of broccoli

Development and evaluation of hinokitiol active paper sheets for the postharvest management of broccoli

Effect of OBS additive on dispersion of MgO in fluorocarbon solvent and deacidification for paper with different ages

Improving the dispersion or suspension of magnesium oxide micro/nanoparticles in fluorocarbon solvent is the key to ensure the efficient and stable deacidification of paper. Here, we chose a dispersant of sodium perfluorononenoxybenzene sulfonate (OBS), to improve the dispersion stability of nano magnesium oxide (nano MgO) in a fluorocarbon solvent without affecting original performance of paper, and then optimized deacidification performance of paper. After addition of OBS, nano MgO was able to stably disperse in fluorocarbon solvent for up to 1 h. With 0.1 wt% OBS, nano MgO could have excellent deacidification effect and good alkali reserves on paper with different ages. In addition, the physical properties had been slightly impacted. MgO is uniformly dispersed in the cross-section of paper fibers, contributing to increasing the strength of paper sheet. Moreover, the paper still showed good resistance to acidification after dry-heat aging. Overall, this work provides an effective and simple paper deacidification method.

Carbon dot-loaded Fe3O4 as photonic pigments for multilevel anti-counterfeiting

Amorphous arrays assembled from colloidal microspheres are a way that obtains angle-independent structural colors. In order to obtain additional properties, colloidal microspheres, which are constituent units, can be modified with other materials. Here, we utilized the silane-functionalized carbon quantum dots (SiCDs) by incorporating them into the Stöber reaction to fabricate Fe3O4@SiO2/SiCDs nanospheres with a core-shell structure. Amorphous colloidal arrays (ACAs) were constructed on commercial printing paper using Fe3O4@SiO2/SiCDs nanoparticles as structural units by a simple permeation assembly. Macroscopically, the prepared ACAs exhibit the magnetic properties of Fe3O4, while under sunlight, they display bright, angle-independent structural colors. Under ultraviolet light, the array shows significant fluorescence. This enables the presentation of multidimensional information under varying magnetic and lighting conditions. By adjusting the thickness of the outer SiO2/SiCDs composite layer, the optical properties and magnetism can be controlled easily. Moreover, due to the strong light absorption capability and high refractive index of Fe3O4, the digital patterns constructed with Fe3O4@SiO2/SiCDs nanospheres demonstrate excellent multi-level anti-counterfeiting characteristics, even under water exposure. The magnetic properties of Fe3O4@SiO2/SiCDs nanospheres, along with their distinct display characteristics under different optical environments, suggest their wide applicability in the fields of multifunctional anti-counterfeiting pigments, bioimaging, and sensing displays.

Competition between slicing and buckling underlies the erratic nature of paper cuts.

By enabling the dissemination and storage of information, paper has been central to human culture for more than a millennium. Its use is, however, associated with a common injury: the paper cut. Surprisingly, the physics underpinning a flexible sheet of paper slicing into soft tissues remains unresolved. In particular, the unpredictable occurrence of paper cuts, often restricted to a limited thickness range, has not been explained. Here we visualize and quantify the motion, deformation, and stresses during paper cuts, uncovering a remarkably complex relationship between cutting, geometry, and material properties. A model based on the hypothesis that a competition between slicing and buckling controls the probability of initiating a paper cut is developed and successfully validated. This explains why paper with a specific thickness is most hazardous (65µm, corresponding, e.g., to dot matrix paper) and suggests a probabilistic interpretation of irregular occurrence of paper cuts. Stimulated by these findings, we finally show how a recyclable cutting tool can harness the surprising power of paper.

Numerical Modelling of Corrugated Paperboard Boxes

Numerical modelling of corrugated paperboard is quite challenging due to its waved geometry and material non-linearity which is affected by the material properties of the individual paper sheets. Because of the complex geometry and material behaviour of the board, there is still scope to enhance the accuracy of current modelling techniques as well as gain a better understanding of the structural performance of corrugated paperboard packaging for improved packaging design. In this study, four-point bending tests were carried out to determine the bending stiffness of un-creased samples in the machine direction (MD) and cross direction (CD). Bending tests were also carried out on creased samples with the fluting oriented in the CD with the crease at the centre. Inverse analysis was applied using the results from the bending tests to determine the material properties that accurately predict the bending stiffness of the horizontal creases, vertical creases, and panels of a box under compression loading. The finite element model of the box was divided into three sections, the horizontal creases, vertical creases, and the box panels. Each of these sections is described using different material properties. The box edges/corners are described using the optimal material properties from bending and compression tests conducted on creased samples, while the box panels are described using the optimal material properties obtained from four-point bending tests conducted on samples without creases. A homogenised finite element (FE) model of a box was simulated using the obtained material properties and validated using experimental results. The developed FE model accurately predicted the failure load of a corrugated paperboard box under compression with a variation of 0.1% when compared to the experimental results.

Enhanced bioremediation of soils contaminated with nicosulfuron using the bacterial complex A12.

To construct an efficient bacterial complex to degrade nicosulfuron and clarify its degradative characteristics, promote the growth of maize (Zea mays), and provide a theoretical foundation for the efficient remediation of soil contaminated with nicosulfuron. Biocompatibility was determined by the filter paper sheet method by mixing Serratia marcescens A1 and Bacillus cereus A2 in a 1:1 ratio, yielding A12. The optimum culture conditions for the bacterial composite were obtained based on a three-factor, three-level analysis using response surface methodology, with 29.25g l-1 for maltodextrin, 10.04g l-1 for yeast extract, and 19.93g l-1 for NaCl, which resulted in 92.42% degradation at 4 d. The degradation characteristics of A12 were clarified as follows: temperature 30°C, pH 7, initial concentration of nicosulfuron 20mg l-1, and 4% inoculum. The ability to promote growth was determined by measuring the ratio of the lysosphere diameter (D) to the colony diameter (d), and the ability of the complex A12 to promote growth was higher than that of the two single strains. Nicosulfuron degradation in sterilized and unsterilized soils reached 85.4% and 91.2% within 28 d, respectively. The ability of the strains to colonize the soil was determined by extraction of total soil DNA, primer design, and gel electrophoresis. The bioremediation effect of A12 was confirmed by the maximum recovery of fresh weight (124.35%) of nicosulfuron-sensitive crop plants and the significant recovery of soil enzyme activities, as measured by the physiological indices in the sensitive plants.

Displays of Devotion

Although Mogao Cave 17 near Dunhuang is renowned as a vast repository of manuscripts and paintings, it also contained a greater volume of printed materials than is commonly represented; and while enigmatic, these surviving artefacts provide windows onto print reception from close to the beginning of the era of mass printing in East Asia. Among the documents recovered from the library cave are thirtyodd illustrated Buddhist prints commissioned in 947 ce by the ruler of Dunhuang, Cao Yuanzhong, which were over fifty years old at the time the cave was sealed. Now scattered across a global network of museums, libraries, and private collections, the prints were transmitted as a consequence of their creative reuse as Buddhist votive objects: the prints, which began their lives as sponsored displays of power, prestige, and merit-generation, passed into new contexts as personalized (often anonymous) devotional objects, displayed and sometimes physically reconfigured using traditional techniques, including mounting, cropping, backing, colouring, and collaging. By considering the alterations made to the Cao corpus of paper prints alongside similar surviving woodblock illustrated prints and portable paintings from Dunhuang, this essay reflects on the forms and significance of the creative uses of the prints of 947 and helps to clarify the relationship between an emerging print culture, traditional technologies, and local Buddhist devotional practices in the tenth century.

Systematic Evaluation of Adhesion and Fracture Toughness in Multi-Material Fused Deposition Material Extrusion.

Material extrusion (MEX) additive manufacturing has successfully fabricated assembly-free structures composed of different materials processed in the same manufacturing cycle. Materials with different mechanical properties can be employed for the fabrication of bio-inspired structures (i.e., stiff materials connected to soft materials), which are appealing for many fields, such as bio-medical and soft robotics. In the present paper, process parameters and 3D printing strategies are presented to improve the interfacial adhesion between carbon fiber-reinforced nylon (CFPA) and thermoplastic polyurethane (TPU), which are extruded in the same manufacturing cycle using a multi-material MEX setup. To achieve our goal, a double cantilever beam (DCB) test was used to evaluate the mode I fracture toughness. The results show that the application of a heating gun (assembled near the nozzle) provides a statistically significant increase in mean fracture toughness energy from 12.3 kJ/m2 to 33.4 kJ/m2. The underlying mechanism driving this finding was further investigated by quantifying porosity at the multi-material interface using an X-ray computed tomography (CT) system, in addition to quantifying thermal history. The results show that using both bead ironing and the hot air gun during the printing process leads to a reduction of 24% in the average void volume fraction. The findings from the DCB test and X-ray CT analysis agree well with the polymer healing theory, in which an increased thermal history led to an increased fracture toughness at the multi-material interface. Moreover, this study considers the thermal history of each printed layer to correlate the measured debonding energy with results obtained using the reptation theory.

Pengaruh Model Pembelajaran Kooperatif Tipe Snowball Throwing Terhadap Hasil Belajar Siswa Pada Mata Pelajaran PAI di SMP Muhammadiyah 07 Blimbing

There is a problem with learning Islamic Religious Education (PAI) which is considered monotonous, making students bored and not interested in studying PAI subjects, even if students are forced, the results will not be optimal. For this reason, a new formulation is needed, which in this case tries to apply a snowball throwing type cooperative learning model to improve student learning outcomes. This research was aimed at finding out the snowball throwing type cooperative learning model at Muhammadiyah 07 Blimbing Middle School as well as knowing the influence of the snowball throwing type cooperative learning model on the learning outcomes of PAI subjects at Muhammadiyah 07 Blimbing Middle School. The snowball throwing type cooperative learning model is where the teacher divides the students into several groups, then after the teacher explains the material each group is given time to study the material again, the teacher prepares questions on sheets of paper then the paper is shaped like a snowball, then thrown to one of the students and the students The person who gets the question thrown is obliged to answer the question.