Pin Type Research Articles

Electrodes: Flat vs Pin-Type Topology in Alkaline Water Electrolysis

The energy transition is already underway, and hydrogen plays a crucial role by enabling renewable energy storage without emitting carbon dioxide and other greenhouse gases. Given the intermittency of renewable energy sources, energy storage is essential in this transition. Hydrogen technologies are recognized as promising solutions. One method to produce green hydrogen is through water electrolysis using renewable energy sources, a process identified with significant potential for decarbonization. However, it needs to enhance efficiency, reduce component costs, and consequently, production costs to expand its adoption. Alkaline water electrolysis for hydrogen production is a mature technology with commercially available megawatt (MW) scale installations. To enhance the performance of alkaline electrolyzers, this study focuses on evaluating flat and pin-type electrodes. To analyze their performance, the electrodes were tested at, 20 degrees Celsius, varying electrode distances between them. Tests were conducted in an electrochemical cell, where different operating voltages were applied incrementally, from 0.1 [V] every 30 seconds, across a range of 0 to 2.7 [V]. From the analyzed distances, the highest current densities were obtained at 1.95 [mm] for the pin type and 4.59 [mm] for the flat. Comparing performances at comparable distances, it is observed that the flat electrode generates a higher current density than the pin type. Although the pin-type electrode increases its surface area by approximately 83%, it hinders the detachment of bubbles, causing them to remain on the electrode’s surface for a longer time and reducing its performance.

Evaluation of tribological parameters for boron carbide and graphite infused aluminium hybrid composite fabricated by stir casting technique

The present work focuses on suggesting Gr as a valuable self-lubricating reinforcement for hybrid composite samples and offering a minimum wear rate for sliding pairs with fewer mechanical surface defects at the same time. A series of samples were fabricated using the route by stir casting method considering B4C and Gr as the two reinforcements. The morphology of the sample has been studied using the X-ray diffraction graphs, Energy dispersive X-ray analysis and Scanning electron imaging stating the homogeneity of reinforcement in various composite cast. The theoretical and experimental density of the series of samples has been studied and compared stating the low porosity of the samples fabricated. A maximum wear rate (Wr) of 0.351 × 10−4 mm3/m. was found for pure aluminium sample against EN31 steel disc with 0.053 as friction coefficient (µ). Wr was somehow seen to reduce up to 0.286 × 10−4 mm3/m for Al-B4C composite with µ of 0.48. For hybrid samples, the wear rate was further seen to improve to 0.187 × 10−4 mm3/m for Al-B4C and Gr 2.0% weight with µ of 0.38. Least Wr was found for composite having Gr 3.5% weight, of 0.149 × 10−4 mm3/m. with µ of 0.36. SEM images of the worn surface give evident results for delamination and crack formation on the pin face for the pure-Al sample. Taguchi-ANOVA analysis has been carried out showing the valid contribution of pin type, load and sliding speed on Wr and friction coefficient as the P-value lies below 0.05 for input parameters considering the 95% confidence level of the model developed. An F-value of 44.57 with R2 of 0.895 is developed for Wr model and an F-value of 54.2 with R2 of 0.934 for the µ model.

Chronic kidney disease: a contraindication for using biodegradable magnesium or its alloys as potential orthopedic implants?

Magnesium (Mg) has gained widespread recognition as a potential revolutionary orthopedic biomaterial. However, whether the biodegradation of the Mg-based orthopedic implants would pose a risk to patients with chronic kidney disease (CKD) remains undetermined as the kidney is a key organ regulating mineral homeostasis. A rat CKD model was established by a 5/6 subtotal nephrectomy approach, followed by intramedullary implantation of three types of pins: stainless steel, high pure Mg with high corrosion resistance, and the Mg–Sr–Zn alloy with a fast degradation rate. The long-term biosafety of the biodegradable Mg or its alloys as orthopedic implants were systematically evaluated. During an experimental period of 12 weeks, the implantation did not result in a substantial rise of Mg ion concentration in serum or major organs such as hearts, livers, spleens, lungs, or kidneys. No pathological changes were observed in organs using various histological techniques. No significantly increased iNOS-positive cells or apoptotic cells in these organs were identified. The biodegradable Mg or its alloys as orthopedic implants did not pose an extra health risk to CKD rats at long-term follow-up, suggesting that these biodegradable orthopedic devices might be suitable for most target populations, including patients with CKD.

Radiographic and complication evaluation of 2 different bioresorbable pins in hallux valgus corrective surgery.

Osteotomies to correct hallux valgus are usually secured using metal implants. Their main disadvantage is the need for a repeat surgery for removal of implanted material. Bioresorbable implants would make it possible to overcome this complication. Few studies analyse the results of using bioresorbable pins. The primary objective of this study is to compare hallux valgus correction radiographic results with the use of two types of bioresorbable pins. The secondary objectives are to screen for possible complications related to the use of these bioresorbable pins. This is a descriptive, retrospective, single-centre study carried out between May 2018 and May 2022 in the orthopaedic surgery department of the Centre Chirurgical Emile Gallé at the CHRU in Nancy (France). The study involved 105 hallux valgus (98 patients) operated on by open double metatarsal and phalangeal osteotomy. Osteotomies were stabilised with resorbable polylactic acid (PLLA) pins (Arthrex® TRIM-IT® drill pin) in 57 cases (53 patients), and with resorbable polylactic acid-polyglycolic acid copolymer (PGLA) pins (Bioretec® ActivaPins®) in 48 cases (45 patients). The efficacy of hallux valgus correction was analysed in terms of changes in preoperative and postoperative radiographic parameters at 1 and 6 months on a weight-bearing foot. Descriptive statistics were used to describe the demographic and radiological parameters of each group. The mean age was 59.7 years (range 25-81 years) in the PLLA group and 56 years (range 23-78 years) in the PGLA group. The mean preoperative HVA was 30° (range 15-63°) in the PLLA group and 30.8° (range 15-57°) in the PGLA group. The mean preoperative IMA was 14.4° (range 7-30°) in the PLLA group and 13.8° (range 7-20°) in the PGLA group. There was a statistically significant correction of hallux valgus in the PLLA (p=5.24 X 10-15 ) and PGLA (p=3.56 X 10-13 ) groups. The mean correction for the hallux valgus angle was 13° in the PLLA group and 12° in the PGLA group. There was no statistically significant difference in hallux valgus correction between the PLLA and PGLA groups, particularly in terms of hallux valgus severity. There was no radiological or clinical complication in the groups related to bioresorbable pins. The use of bioresorbable pins allows effective stabilisation of osteotomies to correct hallux valgus. There was no significant difference in correction between PLLA and PGLA implants, regardless of the severity of the hallux valgus. We did not observe any obvious clinical or radiological complications related to their use. The use of bioresorbable osteosynthesis material in forefoot surgery seems to offer interesting advantages, providing patients with safer and less invasive treatment solutions.

Capillary condensation between nonparallel walls.

We study the condensation of fluids confined by a pair of nonparallel plates of finite height H. We show that such a system experiences two types of condensation, termed single and double pinning, which can be characterized by one (single-pinning) or two (double-pinning) edge contact angles describing the shape of menisci pinned at the system edges. For both types of capillary condensation, we formulate the Kelvin-like equationand determine the conditions under which the given type of condensation occurs. We construct the global phase diagram revealing a reentrant phenomenon pertinent to the change of the capillary condensation type upon varying the inclination of the walls. Asymptotic properties of the system are discussed and a link with related phase phenomena in different systems is made. Finally, we show that the change from a single- to a double-pinned state is a continuous transition, the character of which depends on the wetting properties of the walls.

Comparative analysis on friction fields derived from different bottom pins in the drafting system of ring spinning and their effects on yarn properties

In the drafting process, the strength and distribution of the friction field determines the fiber movement state, affecting the yarn formation process and yarn properties directly. The bottom pin, as an important part in the drafting zone, forms an elastic friction field with the top pin through the apron, which has an important influence on yarn properties. This work is aiming to compare the different friction fields generated by two bottom pins and its mechanical effect on fibers, revealing the influence of the friction field on the quality of yarns with different counts. Theoretical and experimental results show that a larger and stronger friction field was formed by the smaller surface curvature and flatter transition level of bottom pins, imposing a positive effect on the yarn evenness and strength. The difference in evenness between yarns spun with the two types of pins vary from 4.3% to 9.8%, while the yarn spun with a flatter bottom pin has higher strength (maximum difference to 17.1%). This study on the influence of the friction field on yarn properties can clarify the adaptability of different bottom pins for the production of different yarn counts, showing great significance on the actual control of yarn properties and property improvement.

Safety and effectiveness of the three-dimensional-printed guide plate-assisted rotation axis positioning of a hinged external fixator for the elbow.

We aimed to evaluate the safety and effectiveness of three-dimensional (3D)-printed guide plates for assisting in the positioning of the rotation axis of an elbow-hinged external fixator. Terrible triad (TT) patients, who were screened using the predefined inclusion and exclusion criteria, underwent installation of a hinged external fixator on the basis of internal fixation; 3D-printed guide plates, generated from the patient's imaging data, assisted in positioning the rotation axis. All patients received the same peri-operative management and were followed up at six, 12, 24, and 48 weeks postoperatively. The duration of positioning pin placement, the number of fluoroscopies, pin placement success rate, types and incidence of post-operative complications, and the Mayo elbow performance score (MEPS) of the diseased elbow and range of motion (ROM) of both elbows were assessed. In 25 patients who completed the follow-up, the average time required for positioning pin placement was 329.32 ± 42.38 s (263-443 s), the average number of fluoroscopies was 2.32 ± 0.48 times (2-3 times), and the pin placement success rate was 100%. At the last follow-up, the mean MEPS of the diseased elbow was 97.50 ± 6.92 (75-100), with an excellent and good rate of 100%, and all patients demonstrated stable concentric reduction. The average range of flexion and extension was 135.08° ± 17.10° (77-146°), while the average range of rotation was 169.21° ± 18.14° (108-180°). No significant difference was observed in the average ROM between the both elbows (P > 0.05). Eight (32%) patients developed post-operative complications, including elbow stiffness due to heterotopic ossification in three (12%) patients, all of whom did not require secondary intervention. Utilizing 3D-printed guide plates for positioning the rotation axis of an elbow-hinged external fixator significantly reduced intra-operative positioning pin placement time and the number of fluoroscopies with excellent positioning results. Satisfactory results were also obtained in terms of post-operative complications, elbow ROM, and functional scores.

Optimization of Pin Type Single Screw Mixer for Fabrication of Functionally Graded Materials

The direct ink writing (DIW) process, used for creating components with functionally graded materials, holds significant promise for advancement in various advanced fields. However, challenges persist in achieving complex gradient variations in small-sized parts. In this study, we have developed a customized pin shape for an active screw mixer using a combination of quadratic B-Spline, the response surface method, and global optimization. This tailored pin design was implemented in a two-material extrusion-based printing system. The primary objective is to facilitate the transformation of material components with shorter transition distances, overcoming size constraints and enhancing both printing flexibility and resolution. Moreover, we characterized the transition delay time for material component changes and the mixing uniformity of the extruded material by constructing a finite element simulation model based on computational fluid dynamics. Additionally, we employed a particle tracking method to obtain the Lyapunov exponent and Poincaré map of the mixing process. We employed these metrics to represent and compare the degree of chaotic mixing and dispersive mixing ability with two other structurally similar mixers. It was found that the optimized pin-type mixer can reduce the transition delay distance by approximately 30% compared to similar structures. Finally, comparative experiments were carried out to verify the printing performance of the optimized pin-type active mixer and the accuracy of the finite element model.

Analysis of the Decrease in Insulation Resistance of Pin Type Porcelain Insulation at the ULP Ampera of PT PLN (Persero)

Isolators are one of the assets at PT PLN, which serve as separators between the energized and non-energized parts. Maintenance is performed by replacing damaged isolators when there are indications of reduced insulation resistance. In this journal, the insulation resistance values were measured using a Kyoritsu Insulation Tester and six porcelain isolator samples in various conditions were used. The aim was to determine the extent of the decrease in insulation resistance values, as well as the leakage current and touch voltage values based on Ohm's law formula. Based on the measurement results, the sixth isolator in partially damaged condition is the worst, supported by an insulation resistance value of 800 MΩ for a test voltage of 10kV and 400 MΩ for a test voltage of 5kV. In good condition, the measured insulation resistance value of the isolator is 1 TΩ. Based on the calculation results, in the sixth condition, the leakage current values were 6.25 mA and 25 mA, and the touch voltage values, assuming an average human insulation resistance value of 1000 Ω, were 6.25 Volts and 25 Volts. According to 0520-2.K.DIR.2014 standards, the insulation resistance values meet the requirement that 1kV insulation resistance can be sustained by 1MΩ and are still below the maximum touch voltage limit, which is < 50V effective.

The Typology of Pins of Sapalli Culture

In the 70s of the twentieth century, the Sapalli culture of the Bronze Age (2200–1300 BC) that was formed on the territory of Northern Bactria was introduced into scientific discourse, based on studied sources in the direction of historical and archaeological research. The inhabitants of the Sapalli culture were considered extremely skilled in handicrafts in addition to farming and animal husbandry. Among the types of crafts (ceramics, construction, blacksmithing, etc.), jewelry making is especially distinguished by its unique types and forms. The pins that form the basis of jewelry found in the monuments of the Sapalli culture are an important material source for illuminating the culture of the Bronze Age of the people of Central Asia, and, they embody the lifestyle, culture, art, and traditions of the people of the Bronze Age. In addition to other types of jewelry (earrings, diadems, beads, necklaces, bracelets, amulets, rings, and bracelets), many examples of beads have been found in the monuments of Sapallitepe, Djarkutan, Mulalitepe, Bustan VI, VII, Tilla Bulak of Sapalli culture, their typological analysis helps to study their essence in-depth and, the development of their analogues. In this article, more than 140 pins that belong to the class of jewelry for a head identified from the monuments of the Sapalli culture are divided into types, groups, and classes according to the shape of the head part of the pins. Among the types of pins by the shape and purpose, pins with zoomorphic and anthropomorphic figures in the head part, rosette-shaped pins and pins with a star-shaped head part, which are rare artifacts, widespread among the cultures of the Oxus civilization, stand out.

Experimental investigation of forced convection heat transfer for different models of PPFHS heatsinks with different fin-pin spacing

Cooling of electronic components is one of the most important concerns of manufacturers. Using heatsinks with different models is one of the recommended methods for cooling. To compare 12 types of heatsinks, including 3 types of fin-pin heatsinks with rectangular pins, 3 types of fin-pin heatsinks with circular pins, 3 types of fin-pin heatsinks with conical pins, and 3 types of simple fin heatsinks in 5, 7, and 9 fin types regarding forced displacement heat transfer, an experiment was conducted. A special setup designed and built for these types of heatsinks was used to conduct the test. The setup had dimensions of 100 cm × 12 cm x 3 cm with an opening of 120 cm × 120 cm for placing a fan to create airflow with variable speeds and a place for placing the heatsink at the end of the wind tunnel under variable temperatures. The test results showed that the maximum error in the two experimental tests was 6 %. Also, the results showed that in all 4 types of heatsinks, 7-fin pin types had 4 to 20% lower thermal resistance and 20 to 100% higher convection heat transfer coefficient compared to the 5- and 9-fin pin types respectively. When comparing the heatsinks with the same number of fins, it was observed that the 7 and 9-fin types of heatsinks with conical fins have lower thermal resistance and higher convection heat transfer coefficient than other types of heatsinks with the same number of fins, The conical fins having more than 81 % convection heat transfer coefficient compared to the plate fin heatsink. It was also observed that in the 5-pin fin heatsink design, the plate-fin heat sink had the lowest amount of heat resistance due to its higher surface area with the flowing air current.

Research on the examination technology of connector pin skewing according to Blob analysis *

Pin skew detection is an important means to ensure the reliable operation of connectors. To address the issues of low accuracy and limited applicability in existing research, this paper proposes a connector pin skew detection method based on Blob analysis. Firstly, the image is segmented by incorporating the dimensional features of the tested connector to retain the effective information region in the image, reducing the computational workload for subsequent image processing. The image is preprocessed using an improved median filtering algorithm to effectively mitigate the interference of noise on the detection process. Secondly, a locally adaptive approach is employed to dynamically adjust the threshold, and morphological processing is applied to the pin image to enhance the pin speckle features. Subsequently, Blob analysis is utilized to analyze the connector pin speckles, obtaining data on the pin skew. Different evaluation criteria for pin skew data of various connectors are established to achieve quantitative assessment. Finally, experiments are conducted for pin skew detection of single-hole rectangular, double-hole rectangular, and single-hole circular connectors. The experimental results demonstrate that the proposed connector pin skew detection method can effectively detect various types of pin skew in connectors, with a detection accuracy better than 0.05 mm and a repeatability better than 0.03 mm. This method is suitable for automatic detection scenarios of connector pin skew.

Про західнобалтські типи фібул з могильника Острів

The article is devoted to the research of two types of brooches from the Ostriv burial ground in Porossia (Middle Dnipro River region). The morphological characteristics of the objects, the type and chronological attribution and the accompanying archaeological context are considered. In general, seven penannular brooches with connected star-shaped terminals and four ring brooches with ribbed bows were discovered during the first seven years of research at the Ostriv burial ground. All the brooches were recorded in female burials, except two items found in the cultural layer and one brooch with a controversial archaeological context. Together, they make up 23 % of all the clasps found at the territory of the cemetery or 27 % of the brooches discovered in the burial complexes of the necropolis. These types of ancient pins now make up 52 % of women’s burials with brooches. Penannular brooches with connected star-shaped terminals can be divided into two subtypes — larger ones with seven transverse ribs and surface coating with white metal, and slightly smaller ones with six ribs. The damaged brooch from the burial no. 100 stands out for its massiveness and could contain eight or nine decorative ribs, but the item is fragmented, which does not allow clarifying its specific features. Brooches with ribbed bows can also be divided into two subtypes: two items are larger and have twelve decorative ribs on their surface, and two more specimens are slightly smaller and contain seven transverse ribs on the front side. Among the latter two variants can be distinguished — with a concave semicircular and a simple semicircular section of the case. Significantly, the penannular brooch with connected star-shaped terminals and the brooch with ribbed bows with a surface coating of white metal were found in rich burials with neck-rings of the Totenkrone type. Therefore, it is possible to emphasise the probable connection between the objects, the production of which was more time-consuming, with the social position of the deceased during their lifetime, and probably with the chronological factor. Furthermore, only these two types of fibulae among all the categories of jewellery and clothing elements discovered at this necropolis now reliably testify to the long-term habitation and high-quality repair of the objects. In addition, the general features of the repair do not differ from technological receptions within the mother regions of migrants. In conclusion, penannular brooches with connected star-shaped terminals and brooches with ribbed bows had been widespread in the Baltic region during the 11th—12th centuries. However, they were most typical for the population of the South-East Baltic, the medieval Prussians, from whose area they spread among other Baltic, Finnish and Scandinavian people due to trade connections and/or resettlement of groups or individuals within the region (migration of warriors, marriages, etc.). Finally, these types of brooches in the absolute majority of cases are found in the burials of men, mainly in two-tiered cremation burials with a horse and weapons in burial complexes on the territory of the Sambi Peninsula and its adjacent territories. Sometimes such items occur in women’s and children’s burials outside the Prussian area, but they are still more numerous in men’s complexes. Such a contrast of the Ostriv burial ground with synchronous Baltic burial sites seems very interesting, however, conducting a detailed comparative study of the costumes of representatives of the Baltic enclave in Porossia and the female population of the Sambia Peninsula is extremely problematic. The reason is almost absent separated women burials of the 8—13th centuries in the range of the Prussians, because of their dependent social position in this tribe. Thus, it is still impossible to establish whether the materials of the Ostriv burial ground reflect (at least partially) the traditions of medieval Prussian women’s clothing, or whether the composition of the costume underwent significant changes due to migration. The location of these types of brooches in burial complexes in most cases indicates their direct use in a costume to fasten outer clothing — woollen cloaks or capes. However, other provisions are also recorded, which may be related to this population’s peculiarities of burial practices.

Surface Hardening of CP Ti by Laser Hardening and Development of Ti/TiC Surface Composite by Laser Sintering Technique for Wear Resistant Surface

This study deals with the hardening of titanium surface by carburising of CP Ti Gr 2 substrate by using laser sintering process. The objective of this project is to harden the surface to improve surface wear resistance of titanium. In this study graphite powder is used as source of Carbon. Carbon from graphite reacts with titanium and TiC layer of 109 micron was measured on the titanium surface. The microstructure and phase analysis results show that presence of only TiC phase on the surface of the titanium substrate. TiC grains are nearly 5 times finer than titanium substrate grains. Grain refinement of TiC phase all over the surface of the substrate resulted in increase in hardness and development of significant wear resistance surface in titanium substrate. Hardness of TiC layer was found to be 2191Hv which is nearly ten times higher than the substrate titanium. Wear test results of pin and disc type shows negligible wear rate as compared to CP Ti substrate. TiC grains are nearly 5 times finer than titanium substrate grains.

Strength characteristics of post-stump structures used to restore the crown part of teeth in a decompensated form of pathological abrasion

BACKGROUND: Pathological abrasion of hard dental tissues is quite common and can result in the partial or complete destruction of tooth crown, followed by disturbances in the entire dentoalveolar system. Such conditions are difficult to treat because both the esthetic component and functional usefulness must be restored, which is not always possible to achieve in the long term. Currently, various methods in dentistry are used to restore the lost crown part in patients with a decompensated form of pathological tooth abrasion by using various types of pins and pin structures, which do not always allow achieving positive long-term results because of failure and breakage during operation.
 AIM: To assess the strength characteristics of various stump pin inlays and stump structures.
 MATERIALS AND METHODS: Experimental studies of the strength characteristics of various types of stump pin structures were conducted. For this, 45 samples of stump pin structures were made for testing on a ZMGI 250-kp tensile testing machine.
 RESULTS: Experimental results revealed the magnitude of the stress at which sample destruction occurs.
 CONCLUSION: The study obtained information on the strength of various stump pin structures, which are important in tooth-preserving technologies.

鋼種・加力履歴をパラメータとしたCLT鋼板挿入ドリフトピン接合部の引張実験

In recent years, the demand for drift pins connection with inserted steel plate has grown due to its high resisting capabilities. The connection is generally used as tensile joints in CLT shear walls for mid-rise building. Moreover, the effect of different steel types of drift pins, usage of bolts instead of drift pins to prevent the opening of slit, drift pin length and its loading history on structural performances are unclear. Therefore, this study reports the results of tensile tests performed on the CLT drift pins joint with inserted steel plate considering the unknown factors mentioned above.

A PIN photodiode ionizing radiation detector with small angular dependence and low buildup

PurposeTo develop an improved PIN photodiode detector that has low angular dependence and small buildup. Show that the measured dose compares well with the dose calculated by a treatment planning system for static fields at oblique angles and rotationally delivered fields. MethodsCommercially available PIN photodiodes, VEMD1060X01, (Vishay Semiconductor, Shelton, CT), are fabricated into detectors that can be used for measurement of ionizing radiation. PIN photodiodes are soldered onto coaxial cables in an edge-on orientation and are mounted in a symmetrical package. Detector signals are measured with an electrometer with zero input bias voltage. Dose is measured from a Varian Trilogy (Varian Medical Systems, Milpitas, CA) linear accelerators 6 MV photon and 6 MeV electron beams. An Eclipse (Varian Medical Systems, Milpitas, CA) commercial treatment planning system Acuros and electron Monte Carlo algorithms are used for calculating dose expected in various irradiation geometries. ResultsThe single diode detector has an angular dependence between −1.1% and +1.2% and a buildup of 0.6 mm water equivalence. Measurements of dose at 0.3, 0.5, 1.0 and 1.5 cm depth from oblique static beams and from intensity modulated radiation therapy (IMRT) delivered beams agree with planning system calculations within ±1.5%. ConclusionsA clinically useable dose detector can be fabricated from a PIN type photodiode. This diode detector can be used to measure dose at the surface of a patient under a bolus if one is used. Measurements agree with calculations for static fields at oblique angles as well as rotational IMRT delivered beams.

A low insertion loss wideband mm-Wave crossover with three-section branch-line structure based on ridge gap waveguide technology

In this paper, a low insertion loss (IL) wideband millimeter wave (mm-Wave) crossover with three-section branch-line structure based on ridge gap waveguide (RGW) technology is proposed. Firstly, the central-crossover is designed, especially two types of tuning pins are introduced, which greatly improves the performance of the crossover. In addition, in order to facilitate the measurement, the transition from rectangular waveguide (RWG) to RGW is designed. Finally, a prototype is manufactured and measured. The simulation results show that in the frequency range of 28.9 GHz to 36.6 GHz, RL is better than 20 dB, while the isolation levels of |S21|, |S41|, and |S43| are lower than −20 dB, −10 dB, and −20 dB over the same band, respectively. IL is below 0.5 dB in the frequency range of 28.15 GHz to 36.65 GHz. Good consistency was observed between the simulation results and the measurement results.

Heterostyly and pollen dimorphism of <i>Menyanthes trifoliata</i>

<i>Menyanthes trifoliata</i> L., a heterostyly plant, is an endangered species in Korea. Floral morphology has been published for <i>M. trifoliata</i>, but few works have concentrated on pollen dimorphism differences accompanied by floral dimorphism. Here, we conducted a comparative morphological study of two morphs to investigate a dimorphism system with Korean populations. Pollen morphological characteristics were observed with a light microscope and a scanning electron microscope. For the pin type, pollen size is 36.01 ± 2.01 µm, whereas for the thrum type it is 41.28 ± 2.58 µm in terms of the equatorial diameter. The two morphs have a small apocolpium field at 5.62 ± 0.30 for the pin type and 6.24 ± 0.70 for the thrum type. The configuration of the aperture was tricolpate with a striate ridge in the two morphs. However, they have different pollen shapes and sizes, stigma shapes, and apocolpium sizes. <i>M. trifoliata</i> only has different pollen sizes and shapes between European populations and Korean populations. Nevertheless, Korean populations also show pollen dimorphism correlated with their floral dimorphism.

Effect of temperature on the tribological characteristics of A356/15 wt.% SiCp functionally graded composites in unidirectional contact

In this paper, preparation of A356-15 wt.% SiC particle reinforced functionally graded metal matrix composite[FGMMC] was done using a vertical centrifugal casting machine and elevated temperature (350 °C) tribological characteristics were reported in unidirectional sliding contact. The operating parameters of tribo pair tested were fixed with a load in the range of 15 N to 45 N under a constant sliding speed of 1 m/s slid through 350 m. The gradient distribution of FGMMC disc was evaluated using optical microscopy. Hardness values were obtained from the Brinell hardness tester and found to be well correlated with the obtained microstructures. Two types of wear and friction test pins were prepared from the disc for the elevated temperature tribo testing, one obtained from the FGM's outer zone, when the particle concentration is at its highest, and another taken from the inner zone, where the matrix concentration is at its highest. According to the wear results, both test pins exhibit an increase in wear rate as the load increases. Furthermore, for all loads, it is found that the test pin from the matrix rich portion has a higher wear rate than the test pin from the particle rich portion. At high temperatures, higher coefficients of friction are seen in the pins of the matrix rich portion, while lower coefficients of friction are observed in the test pins of the particle rich portion. The SEM images reveal that for test pins obtained from matrix rich portions, adhesion and metal flow are the main wear mechanisms, and for test pins taken from particle rich portions, abrasion, delamination and severe plastic deformation. It was observed that the pin tested in the matrix-rich region generates plate-like debris, whereas the pin tested in the particle-rich portion generates powdery-type debris.