Tip Surface Research Articles

Karakteristik Buah dan Biji Lontar (Borassus Flabelifer L.)

The purpose of this study was to provide the data about character of lontar fruit and seeds in Kefamenanu City, North Central Timor Regency. This research was conducted from August to September 2022 using exploration and sample collection methods than contnued with characterization of fruit and seed. The results showed that the lontar fruit and seed in Kefamenanu can be characterized using the characteristics of the diameter of the base of the petals, the diameter of the tip of the petals, the length of the inner petals, the length of the outer petals, the width of the inner petals, the width of the outer petals, the number of petals, color. petals, edges of petals, petal shape, weight of petals, weight of fruit with petals, weight of fruit without petals, fruit diameter, fruit length, fruit circumference, fruit skin color, fruit shape, fruit skin surface, fruit tip and base surface, base color and fruit tip, seed weight, seed length, seed width, seed diameter, endosperm diameter, seed coat thickness, endosperm length, and endoperm color. In conclusion, there are 31 qualitative and quantitative characters that have been used to characterize lontar fruit and seed in Kefamenanu City.
 Keywords: Fruit and Seed Characters, Lontar

Autofluorescence spectral analysis for detecting urinary stone composition in emulated intraoperative ambient

The prevalence and disease burden of urolithiasis has increased substantially worldwide in the last decade, and intraluminal holmium laser lithotripsy has become the primary treatment method. However, inappropriate laser energy settings increase the risk of perioperative complications, largely due to the lack of intraoperative information on the stone composition, which determines the stone melting point. To address this issue, we developed a fiber-based fluorescence spectrometry method that detects and classifies the autofluorescence spectral fingerprints of urinary stones into three categories: calcium oxalate, uric acid, and struvite. By applying the support vector machine (SVM), the prediction accuracy achieved 90.28 % and 96.70% for classifying calcium stones versus non-calcium stones and uric acid versus struvite, respectively. High accuracy and specificity were achieved for a wide range of working distances and angles between the fiber tip and stone surface in an emulated intraoperative ambient. Our work establishes the methodological basis for engineering a clinical device that achieves real-time, in situ classification of urinary stones for optimizing the laser ablation parameters and reducing perioperative complications in lithotripsy.

Interaction Mechanism of Transonic Squealer Tip Cooling With the Effect of High-Speed Relative Casing Motion

Abstract The relative casing motion can significantly influence the turbine blade tip aerothermal performance. In this study, experimental investigation was conducted in a newly developed high-speed disk rotor rig which can mimic engine realistic high-speed casing relative motion while enabling full optical access to a transonic turbine blade tip surface. Spatially-resolved tip heat transfer data, including heat transfer coefficient and film cooling effectiveness, were obtained for a cooled transonic squealer tip by infrared transient thermal measurement. Combined with closely coupled Reynolds-averaged Navier–Stokes computational fluid dynamics (CFD) analysis, this paper reveals an interesting interaction mechanism between the cooling injections from the pressure side and the cavity floor with and without the effect of relative casing motion. Both experimental data and CFD results show a consistent trend in both heat transfer and cooling performance. With cavity cooling only, the cooling performance reduces with the effect of relative casing motion. However, with additional cooling injection from the pressure side, a significant improvement in the combined cooling performance with the relative casing motion can be observed. Such opposite trend highlights the importance of relative casing motion when ranking different tip cooling designs. With the consideration of relative casing motion, extra tip cooling benefit can be obtained by combining cooling injections from two different locations.

Tribological Properties of TiN Coating on Cotton Picker Spindle

The spindle is the key working part of the horizontal cotton picker, and the wear resistance of its surface directly affects the service life of the spindle. Improving the surface performance of the spindle is fundamental for improving the performance of cotton pickers. To enhance the wear resistance of the spindle surface, this study used the physical vapor deposition (PVD) technique to prepare TiN coating on the spindle substrate surface of the cotton-picking machine to improve the spindle surface rather than the original electroplated chromium coating. The microscopic morphology of the spindle was analyzed by scanning electron microscope (SEM), the mechanical and frictional properties of the spindle were tested by a nanoindentation tester and a friction wear tester, and the morphology of the worn spindle was observed by a portable microscope and a 3D surface profiler. The test results indicated that after the PVD treatment, the surface hardness of the spindle was about 2.5 times that of the electroplated chromium spindle, and the H/E value was 2.2 times that of the electroplated chromium spindle. PVD-TiN spindle showed better mechanical properties. In the friction test, under the same conditions, the wear rate of the PVD-TiN spindle was less than that of the chrome plating spindle. In a field test of 100 hm2, the average wear area of the second tooth tip surface of the electroplated chromium spindle was about 2.17 times that of the PVD-TiN spindle. It was verified that the PVD-TiN spindle surface had better wear resistance than the electroplated chromium spindle. This study has certain research significance for the performance optimization of cotton pickers. Also, it is indicated that PVD-TiN coating can effectively improve the wear resistance of the spindle surface and provides a new method for enhancing the service life of the spindle.

Effects of pressure side film cooling hole placement and condition on surface heat transfer coefficients along a transonic turbine blade tip

Considered is thermal performance for the squealer blade tip of four film cooling configurations, B1, B2, B3 and B4, with hole exits for each arrangement positioned along a different portion of the upper pressure side of a transonic turbine blade. Each upper pressure side configuration includes five film cooling holes, such that each hole has a compound angle of 45° with respect to the circumferential/axial plane, also with an angle orientation of 40° relative to the plane tangent to the exit cross sectional area of each hole. Results are given for blowing ratios ranging from 0.42 to 3.20 in the form of spatially-resolved and spatially-averaged surface distributions of heat transfer coefficients and heat transfer coefficient ratios. In regard to tip surface variations, surface heat transfer coefficient ratios distributions are a consequence of the manner in which the film coolant collects in a substantial manner along the pressure side rim and then advects above and across the squealer recess with little to no coolant collecting within the cavity, or along the recess surface, to then collect in a substantial manner further downstream along the suction side rim. Such flow characteristics affect heat transfer coefficient ratio variations for all four film cooling configurations, but are especially influential for the B3 arrangement. Considering local heat transfer coefficient ratio distributions along the upper pressure side surface, the most significant local variations in the vicinity of a film cooling hole exit locations. Here, heat transfer coefficient ratio distributions for the B1 and the B4 configurations, in particular, show evidence of a horseshoe-shaped vortex which forms around each emerging coolant concentration. The two downstream legs of each vortex are associated with a pair of locally augmented heat transfer coefficient streaks, often with a streak of locally-lower coefficient ratios positioned between. Local and line-averaged heat transfer coefficient ratios along the upper pressure side also vary significantly with blowing ratio, with additional periodic variations as the normalized circumferential/axial coordinate varies. Within the resulting distributions, local heat transfer coefficient ratio increases are associated with locally augmented mixing and turbulent transport, which are especially present near the exits of different film cooling hole locations.

Patterning of Hydrophilic and Hydrophobic Gold and Magnetite Nanoparticles by Dip Pen Nanolithography (Small 18/2023)

Dip Pen Nanolithography In article number 2208069, Bart Jan Ravoo and co-workers report the surface patterning of nanoparticles using dip pen nanolithography. Metal and metal oxide nanoparticles functionalized with various organic ligands can be patterned in nanosized clusters. Depending on the polarity of the ligand shell, water or toluene is used as ink solvent. No modification of atomic force microscope (AFM) tip or substrate surface is required.

Evaluation of spatial distribution of the oxidation of glass beads simulating soil using high-voltage pulsed discharge

The spatial distribution of soil oxidation using a high-voltage pulse generator was evaluated using indigo carmine. The results showed that the amount of indigo carmine decolorization increased with increasing charging voltage and energy input. It was also found that the decolorization of indigo carmine occurred on the surface of the needle electrode, in the discharge path, and near the ground electrode. The probability of discharge penetrating soil increased with decreasing the gap length between the electrode tip and soil surface, which promoted the decolorization reactions. The amount of indigo carmine decolorization per volume decreased with increasing soil depth. When the soil depth was large, discharges reaching the ground electrode could not be confirmed. This suggests that the oxidation reaction of indigo carmine depends on a discharge that penetrates the soil.

“Tip effect” of hexagram-like Co-doped MoC heterostructure for hydrogen evolution reaction

It is urgent to develop an efficient and durable transition metal based electrocatalyst to overcome the slow water dissociation kinetics of the alkaline hydrogen evolution reaction (HER). Thus, a novel hexagram-like porous N-doped Co/MoC Mott–Schottky electrocatalyst (Co/MoC@NC) derived from Zn/Co ZIF-L doped with phosphomolybdic acid hydrate (POM) was developed for alkaline HER. The abundant Mott–Schottky interfacial heterostructures provided sufficient active sites, which accelerated electron and mass transport. DFT calculations indicated that Co/MoC Mott–Schottky heterostructure accelerated water adsorption and dissociation. COMSOL simulations showed that the “tip effect” of hexagram-like structures provided a localized field with high electric charges. The resulting H+-rich tip surface promoted alkaline reaction kinetics to improve HER performance. The Co/MoC@NC catalyst exhibited an excellent HER performance with a low overpotential of 80.6 mV at a current density of −10 mA/cm2 in 1 M KOH.

Mode I fracture behavior of heterogeneous granite: Insights from grain-based FDEM modelling

The failure of brittle rock has a significant influence on engineering stability. The purpose of this study is to understand the progressive fracture mechanism of heterogeneous granite from a mesoscopic perspective. In the present work, the fracture process zone (FPZ) model is used to characterize the constitutive relationship of rock cracking in the combined finite-discrete element method (FDEM). Moreover, the breakable grain-based model (bGBM) is established to study the fracture behavior of granite via the semi-circular bending (SCB) tests. To rebuild the meso-structure of granite specimens, an algorithm that considers the mesoscopic grain geometry characteristics and grain contact mechanical properties is utilized. Then, three classic examples, namely, a uniaxial compressive test, a Brazilian splitting test and a semi-circular bending test, are investigated with the numerical model. A good agreement of the load–displacement curves and crack propagation paths can be found between the simulation and laboratory tests. The meso-heterogeneity of granite cause the macroscopic fracture surface of the slit tip to be nearly upright, with local roughness and zigzag. The slit length has a significant effect on the damage distribution range of the SCB specimen, and the peak load and mode I fracture toughness decreases with increasing slit length and supporting span. The accurate measurement of the mode I fracture toughness of SCB specimens needs to consider the FPZ, and the average increment is 39% and 41% under different slit length and supporting span conditions, respectively.

A Numerical Study on the Flap Side-Edge Noise Reduction Using Passive Blowing Air Concept

The flap side-edge is a vital contributor to airframe noise. In this study, we propose a novel flap side-edge noise reduction method based on the concept of active blowing air. A long slot is opened from the flap’s lower surface to the tip surface to induce a secondary jet flow, which is driven by the local pressure difference between the flap’s lower surface and the tip surface. The unsteady flow field around the flap side-edge was computed by the lattice Boltzmann solver PowerFLOW, and the far-field noise was predicted by the FW-H equation. It is demonstrated that the dominant features of the flap side-edge flow are the double vortex structures, and the new passive blowing air reduction method can achieve about 3.3 dB noise reduction. Moreover, the underlying noise reduction mechanism has been analyzed and revealed. It is shown that the secondary jet flow from the long slot on the flap side-edge would dissipate the flap side-edge vortex and displace the flap side-edge vortical structure away from the flap surface, thus resulting in a decrease in the pressure fluctuations on the flap side-edge surface. As a result, the flap side-edge noise was reduced. In contrast to the current active air blowing technique, the newly proposed blowing air technique is passive and quite simple and does not require an extra air source or control system. This novel flap side-edge noise reduction technology provides a new flow control strategy and noise reduction methodology and can be further optimized.

Automatic control of soil puncture

Among the existing methods of making horizontally directed wells for trenchless laying of utilities, the method of static soil puncture is the most popular. The main disadvantage of this method is poor accuracy of the piercing head movement in the soil. This drawback requires constant adjustment of the trajectory of this movement. The movement of the head is controlled by using a head with an asymmetric tip and the action of translational and translational-rotational motion on it. The transmission of these movements from the power plant is accomplished by means of a set of fixed pushing rods. If you know how the process of off and on deviation of the head happens, you can make it possible to automatically control the puncture of the soil by timely changing the direction of the head tip shift.
 To achieve this goal, the following issues have been resolved. It is determined that for automated control of the soil puncture process by static method it is necessary to use a puncture head with an asymmetric tip. Changing its position in the soil space can be controlled by rotating the tip and orienting it according to the direction of deviation.
 The obtained mathematical model of correcting the trajectory of the head with a truncated cylindrical tip makes it possible to predict the process of soil puncture in time depending on different soil conditions and to get a solution to the problem of deviation from the specified design trajectory of the tip head which has a recognized angle of the frontal plane cut to the horizon with successive build-up of rods.Changing the orientation in the space of the cut front surface of the cylindrical tip, taking into account the obtained mathematical model of correcting the trajectory of the head in the soil, allows to increase the span length to 100 m due to the proposed automated principle of correcting its movement.

Novel type of whisker-tip cantilever based on GaN microrods for atomic force microscopy

High-resolution scanning probe microscopy (SPM) is a fundamental and efficient technology for surface characterization of modern materials at the subnanometre scale. The bottleneck of SPM is the probe and scanning tip. Materials with stable electrical, thermal, and mechanical properties for high-aspect-ratio (AR) tips are continuously being developed to improve their accuracy. Among these, GaN is emerging as a significant contender that serves as a replacement for standard Si probes. In this paper, for the first time, we present an approach that demonstrates the application of GaN microrods (MRs) as high-AR SPM probes. GaN MRs were grown using molecular beam epitaxy, transferred and mounted on a cantilever using focused electron beam-induced deposition and milled in a whisker tip using a focused ion beam in a scanning electron/ion microscope. The presence of a native oxide layer covering the GaN MR surface was confirmed by X-ray photoelectron spectroscopy. Current-voltage map measurements are also presented to indicate the elimination of the native oxide layer from the tip surface. The utility of the designed probes was tested using conductive atomic force microscopy and a 24-hour durability test in contact mode atomic force microscopy. Subsequently, the graphene stacks were imaged.

Biofilm formation and antibiotic resistance among Coagulase Negative Staphylococcus species isolated from central venous catheters of intensive care unit patients.

This study was conducted to determine the biofilm formation of coagulase negative Staphylococcus species (CoNS) isolated from patients with catheter related blood stream infection (CRBSI) and colonized central venous catheters (CVC) and their antibiotic susceptibility patterns and in situ biofilm formation of CVC tips. Eighty-two CoNS isolated from intensive care unit (ICU) patients with CRBSI (n​=​8) or colonized CVC (n​=​74) were included. Species identification and antibiotic susceptibility test were done. All isolates were screened for biofilm formation using crystal violet and 3-(4,5-dimethylthiazole-2-yl)-2-5-diphenyl-2H-tetrazolium bromide (MTT) assays and categorized as strong or moderate biofilm formers. CVC tips were subjected to crystal violet stain and scanning electron microscopy (SEM) to detect in-situ biofilm formation. Staphylococcus haemolyticus (n​=​34; 41%) was the commonest to cause both CRBSI and CVC colonization. All 82 CoNS produced biofilms. Among them 77 (93.90%) were strong biofilm formers including all from CRBSI patients and 05 (6.10%) were moderate biofilm formers as detected by both methods. SEM showed bacteria adhered to surfaces of CVC tips with microbial-aggregates embedded in extracellular matrix. Mean crystal violet absorbance of CVC from CRBSI patients (0.6628) was significantly higher than colonized CVC (mean value 0.5592) (p​=​0.030). S.haemolyticus showed higher resistance to cloxacillin compared to other CoNS (p​=​0.039). Majority of CoNS isolated were strong biofilm formers. In-situ biofilm formation on CVC tips were significantly evident in CRBSI patients compared to CVC colonized patients. S.haemolyticus is the commonest to cause both CRBSI and CVC colonization and shows significantly higher cloxacillin resistance rate.

Hydrogen-surface interaction from first-principles calculations and its implication to hydrogen embrittlement mechanisms of titanium

Hydrogen embrittlement (HE) caused by the interaction between hydrogen and crack tip is the key factors for the stress corrosion crack (SCC) of titanium alloys utilized in marine environment. In the present work, the interactions between hydrogen and the fresh surface of crack tip in titanium, including the adsorption, desorption, diffusion of hydrogen atom near the surface, are investigated systematically by using a first-principles method. The surface energy of titanium with H adsorption is calculated. We show that H atoms are prone to adsorb on the surface of titanium and then accumulate beneath the surface whereas both desorption of H atoms to form H2 and diffusion of H atom into bulk cost energy. The surface energy decreases with increasing coverage of H, which reduces the fracture work of titanium. The H-induced reduction of the fracture work at the crack tip is expected to accelerate the crack propagation. The accumulation of H beneath the surface facilitates the formation of hydride ahead the crack tip which is critical for the hydride induced embrittlement. The H2 pressure mechanism is not supposed to be responsible for the HE of titanium because the desorption of H atoms from the surface to form H2 is energetically unfavorable.

Effect of annealing on the magnetic anisotropy of GaMnAsP layers with graded P concentration

We have investigated the effect of annealing on the magnetic anisotropy of MBE-grown GaMnAs1−yPy film in which phosphorus content varies from 0% to 24% along the growth direction. Such variation is achieved by growing a series of GaMnAs1−yPy layers in which y is successively increased. Hall effects measurements on an as-grown graded film reveal that the bottom 80% of the film has in-plane easy axes, 10% has both in-plane and perpendicular easy axes, and the remaining 10% has a vertical easy axis. Such gradual change of magnetic anisotropy in the film from in-plane to perpendicular with increasing P concentration is in accordance with the continuous variation of strain from compressive to tensile as the P concentration increases the bottom of the film to tensile toward its tip surface. However, thermal annealing significantly changes the magnetic anisotropy of the graded GaMnAs1−yPy film. In particular, the intermediate region having both in-plane and perpendicular easy axes nearly disappears in the film after annealing, so the film is divided into two types of layers having either only in-plane or only perpendicular anisotropy. These dramatic changes in magnetic anisotropy of the graded GaMnAs1−yPy film introduced by annealing suggest that one can strategically use this process to realize orthogonal magnetic bilayers consisting of in-plane and perpendicular easy axes.

Vertebral Endplate Concavity in Lateral Lumbar Interbody Fusion: Tapered 3D-Printed Porous Titanium Cage versus Squared PEEK Cage

Background and Objectives: To prevent postoperative problems in extreme lateral interbody fusion (XLIF), it is critical that the vertebral endplate not be injured. Unintentional endplate injuries may depend on the cage. A novel porous titanium cage for XLIF has improved geometry with a tapered tip and smooth surface. We hypothesized that this new cage should lead to fewer endplate injuries. Materials and Methods: This retrospective study included 32 patients (mean 74.1 ± 6.7 years, 22 females) who underwent anterior and posterior combined surgery with XLIF for lumbar degenerative disease or adult spinal deformity from January 2018 to June 2022. A tapered 3D porous titanium cage (3DTi; 11 patients) and a squared PEEK cage (sPEEK; 21 patients) were used. Spinal alignment values were measured on X-ray images. Vertebral endplate concavity (VEC) was defined as concavity ≥ 1 mm of the endplate on computed tomography (CT) images, which were evaluated preoperatively and at 1 week and 3 months postoperatively. Results: There were no significant differences in the patient demographic data and preoperative and 3-month postoperative spinal alignments between the groups. A 3DTi was used for 25 levels and an sPEEK was used for 38 levels. Preoperative local lordotic angles were 4.3° for 3DTi vs. 4.7° for sPEEK (p = 0.90), which were corrected to 12.3° and 9.1° (p = 0.029), respectively. At 3 months postoperatively, the angles were 11.6° for 3DTi and 8.2° for sPEEK (p = 0.013). VEC was present in 2 levels (8.0%) for 3DTi vs. 17 levels (45%) for sPEEK (p = 0.002). After 3 months postoperatively, none of the 3DTi had VEC progression; however, eight (21%) levels in sPEEK showed VEC progression (p = 0.019). Conclusions: The novel 3DTi cage reduced endplate injuries by reducing the endplate load during cage insertion.

Stripping mechanism and Gaussian distribution model of a concave bionic comb for stripping prior to cutting

Stripping prior to cutting is a harvesting technique that only strips rice grains and obtains complete straws. This paper aims to solve the problems of high loss rate and short throwing distance for stripping prior to cutting. A concave bionic comb was developed based on the filiform papilla structure on the surface of a cattle tongue tip. The mechanism analysis and comparative research of the flat comb and the bionic comb were carried out. The results showed that when the arc radius was 5.0 mm, the magnification ratio of filiform papilla was 4.0, and the concave angle was 60°, the loss rate of falling grain was 4.3 %, and the loss rate of uncombed grain was 2.8 %. The diffusion angle of bionic comb was smaller than that of flat comb. The distribution characteristics of the thrown materials conformed to Gaussian distribution. Under the same working conditions, the falling grain loss rate and uncombed loss rate of the bionic comb were always lower than that of the flat comb. This study provides reference for the cross application of bionic technology and crop production field, promotes the harvesting way application of stripping prior to cutting in gramineous plants such as rice, wheat and sorghum, and provides a basis for harvesting the whole straws and expanding the way of comprehensive utilization of straws.

Aryldiazonium reduction mechanism deciphered by scanning electrochemical microscopy through an EC’ process

Homogeneous redox catalysis, often associated to EC’ mechanisms, is an elegant way to investigate electron transfer processes. Among the electrochemical tools employed to decipher such processes, scanning electrochemical microscopy (SECM) is a powerful technique to unravel complex EC’ mechanisms, especially those involving short life time intermediates. Herein, it is employed to decipher the mediated reduction of 4-nitrobenzenediazonium by the reduced form of a redox mediator, chloranil, electrogenerated at the tip of the SECM. This strategy that relocates the reduction of the aryldiazonium far from the tip surface allows protecting the tip from passivation and producing very reactive intermediates, i.e. aryl radicals, in solution. Combined with simulations, the SECM in the feedback mode allows describing the whole reduction mechanism and evidences the reaction pathway implying reactive radical species issued from the aryldiazonium reduction. Particularly, it is demonstrated that an irreversible reaction occurring between the aryl radical and the redox mediator is a predominant side reaction.

Dielectric Characterization of Healthy Human Teeth from 0.5 to 18 GHz with an Open-Ended Coaxial Probe.

Dental caries is a major oral health issue which compromises oral health, as it is the main cause of oral pain and tooth loss. Early caries detection is essential for effective clinical intervention. However, methods commonly employed for its diagnosis often fail to detect early caries lesions, which motivates the research for more effective diagnostic solutions. In this work, the relative permittivity of healthy permanent teeth, in caries-prone areas, was studied between 0.5 and 18 GHz. The reliability of such measurements is an important first step to, ultimately, evaluate the feasibility of a microwave device for caries detection. The open-ended coaxial probe technique was employed. Its performance showed to be compromised by the poor probe-tooth contact. We proposed a method based on applying coupling media to reduce this limitation. A decrease in the measured relative permittivity variability was observed when the space between the probe tip and tooth surface was filled by coupling media instead of air. The influence of the experimental conditions in the measurement result was found to be less than 5%. Measurements conducted in ex vivo teeth showed that the relative permittivity of the dental crown and root ranges between 10.0-11.0 and 8.0-9.5, respectively.

Attosecond field emission

Field emission of electrons underlies great advances in science and technology, ranging from signal processing at ever higher frequencies1 to imaging of the atomic-scale structure of matter2 with picometre resolution. The advancing of electron microscopy techniques to enable the complete visualization of matter on the native spatial (picometre) and temporal (attosecond) scales of electron dynamics calls for techniques that can confine and examine the field emission on sub-femtosecond time intervals. Intense laser pulses have paved the way to this end3,4 by demonstrating femtosecond confinement5,6 and sub-optical cycle control7,8 of the optical field emission9 from nanostructured metals. Yet the measurement of attosecond electron pulses has remained elusive. We used intense, sub-cycle light transients to induce optical field emission of electron pulses from tungsten nanotips and a weak replica of the same transient to directly investigate the emission dynamics in real time. Access to the temporal properties of the electron pulses rescattering off the tip surface, including the duration τ = (53 as ± 5 as) and chirp, and the direct exploration of nanoscale near fields open new prospects for research and applications at the interface of attosecond physics and nano-optics.