Double Blade Research Articles

Pressure pulsation of pump turbine at runaway condition based on Hilbert Huang transform

Pumped storage is an important component of electrified wire netting. The safe and stable operation of pump turbines is extremely important. Among them, pressure pulsation is one of the main causes of pump turbine vibration. The characteristics of pressure pulsation are relatively complex, and it is difficult to directly observe their temporal changes using commonly used FFT methods. The division of frequency characteristics is often vague. Meanwhile, it is difficult to explain some phenomena such as frequency doubling. This article focuses on a certain model of pump turbine and uses SST model to numerically simulate the runaway condition of the pump turbine. And the Hilbert Huang transform method is used to analyze the pressure pulsation in the vaneless region and draft tube. The results show that the main characteristic frequencies of the vaneless region are blade passing frequency 112.5 Hz and rotational frequency 12.5 Hz. The main characteristic frequencies of the draft tube are vortex rope frequency near 3 Hz which energy ratio is up to 50%, rotational frequency, and blade passing frequency. The pressure pulsation characteristics in the vaneless region have changed from a complex composition of double blade passing frequency and rotational frequency to a distribution dominated by blade passing frequency. In the passage of the guide vane, the pressure pulsation is almost only characterized by blade passing frequency. The frequency characteristics of the vaneless region between the runner and the guide vane become complex again. Meanwhile, the results show that the characteristic frequencies of the vaneless region and the draft tube propagate upstream and downstream.

OPTIMIZING THE TIBIAL KEEL SLOT FOR THE OXFORD UNICOMPARTMENTAL KNEE ARTHROPLASTY

Tibial periprosthetic fracture is an important complication of the Oxford Unicompartmental Knee Replacement (OUKR). Primary fixation of cementless OUKR tibial components relies on the interference-fit of the ‘keel’ and a slot in the proximal tibia. Clinically used double blade keel saws (DKS) create slots with two grooves, generating stress concentrations where fractures may initiate. This study aimed to investigate slot factors that may influence incidence of tibial periprosthetic fractures.Slots were made in PCF20 polyurethane foam using the DKS plus/minus adjuvant rasping, single blade keel saw (SKS), and rasp-only. Round and square slots were machined with milling cutters. Compact tensile tests were conducted per ASTM E399 to determine tensile load to fracture (TLTF) and results were validated using bovine tibia. Cementless OUKR components were implanted into slots in custom polyurethane blocks and compressed to failure to determine anatomical load to fracture (ALTF). A custom MATLAB program calculated slot roundness from cross-sectional images.Round slots had higher TLTF (29.5N, SD=2.7) than square (25.2N, SD=1.7, p<0.05) and DKS slots (23.3N, SD=2.7, p<0.0001). Fractures occurred at the round slot apices, square slot corners, and deepest DKS slot grooves. ALTF was not significantly different between square and round slots. Adjuvant rasping made DKS slots significantly rounder, resulting in significantly higher TLTF, but rasping did not increase ALTF. ALTF was significantly higher for SKS (850N, SD=133, p<0.01) and rasp-only (912N, SD=100, p<0.001) slots compared to standard DKS slots (703N, SD=81).Round keel slots minimise stress concentrations and increase TLTF but do not increase ALTF. The SKS and rasp-only slots retain material at slot ends and have significantly higher ALTF. Future studies should assess saw blades that retain material and round slot ends to evaluate if their use may significantly reduce the incidence of tibial periprosthetic fracture.

TO ISSUE INCREASING THE EFFICIENCY OF THE MASS TRANSFER PROCESS IN AGITATORS

This study investigates the impact of impeller design on the rate of esterification reaction in a batch reactor. Different impeller designs were tested and compared, including Backswept impeller, C-shaped, Double Blade impeller, and Pitched impeller. The results showed that the choice of impeller design has a significant effect on the rate of esterification reaction, with the Backswept impeller proving to be the most effective. In this work, it is aimed to investigate the esterification of acetic acid and methanol in a batch stirred reactor for the synthesis of methyl acetate. The temperature range of 303.15 K is examined, with sulphuric acid used as the homogeneous catalyst in varying concentrations of 0.0633 mol·L1 to 0.3268 mol·L-1. The feed molar ratio of acetic acid to methanol also varied from 1:1 to 1:4 to observe its influence on the reaction rate. The research delves into the effects of temperature, catalyst concentration, and reactant concentration on the reaction rate. The experimental data is correlated using a second-order kinetic rate equation, and the forward and backward reaction rate constants and activation energies are determined from the Arrhenius plot. The developed kinetic model is compared with previous models in literature. In order to find the most effective impeller for esterification reaction, diameter of impellers was accepted same in the constant volume and dimension of batch reactor. The obtained kinetic equation proves useful for the simulation of a reactive distillation column for the synthesis of methyl acetate. Keywords: the batch reactor, impeller, esterification, effectivity, mass transfer, mixing, mechanical mixers, Logarithmic Shear Rate, Eddy Diffusivity.

Visualization research of energy dissipation in a pump turbine unit during turbine mode's starting up

Identifying the precise location of flow energy dissipation (FED) in pump turbines is crucial for enhancing the stability of pumped storage power stations. In this study, the transient process of the turbine mode's starting up in the pump-turbine has been simulated to examine the FED locations by using the one-dimensional and three-dimensional (1D-3D) coupled computational fluid dynamics (CFD) method. This analysis pinpoints high FED locations in each component of the pump-turbine. The observations reveals that the trailing edge of the guide vane consistently demonstrates high FED values, while wall shear stress, axial and radial forces had a significant effect on flow characteristics. Moreover, high FED sites correspond to high turbulence kinetic energy locations. Continuous wavelet transform (CWT) has been applied to examine the time-frequency characteristics during this process. Low frequency (fc = 0.12) has been identified as the dominant frequency in the volute. In the draft tube, the wavelet magnitude of the double blade passing frequency (fc = 18) is 30.4% of that under the dominant frequency (fc = 9). Regional visualization of FED offers a valuable method for the in-depth understanding of energy dissipation in pump turbines and improving operational stability in pumped storage power stations.

BATTLE AXES OF AMAZONS OF EUROPEAN SCYTHIA

Weapons are one of the most important elements of the material culture of the North Pontic nomads. Archaeological finds from the steppe kurhans testify that the Scythians were armed with bows and arrows, spears and javelins, slings, swords and daggers, battle axes, horseman’s picks (pick axe), hammers and maces. However, not all types of weapons were equally common, and battle axes were less popular.
 Relatively few battle axes came from burial assemblages on the territory of European Scythia — from 50 to 100 items, according to the data of various researchers. By morphological features, two groups are distinguished: battle axes (three divisions) and axes with hammers (two divisions). The length of the wooden handles in most cases is about 50―70 cm. Battle axes are known in Scythian burial sites from the 7th to the 2nd century BC. Finds of early specimens are correlated mainly with antiquities of the Forest Steppe, while later specimens are concentrated in the central part of the territories of European Scythia. Until recently, it was believed that this type of weapon marked only male Scythian burials, however, the presence of axes in several female burials proves otherwise.
 The use of axes by the Amazons is mentioned in the works of several ancient authors, the works of ancient art demonstrate this phenomenon as well. According to archaeological materials, battle axes were found in only six (2 %) women’s graves: two in the Lower Dnipro Steppe Group and four in the Lower Dniester Steppe Group. An examination of the burial complexes of Scythian female warriors with axes made it possible to note several characteristic features.
 
 All axes are iron. Five of them have a single blade, from 16.5 to 22 cm long. And only one axe has a double blade. It is also stand out by its small size — 14.6 cm. Typologically and in terms of size, all these axes fully correspond to samples from other Scythian graves of European Scythia.
 An examination of the placement of axes in the graves showed a variety of its options. This means that there were no clear canons for the location of axes regarding the dead.
 The nature and size of the burials, as well as the assortment and number of grave goods testify that Scythian female warriors armed with axes were mainly representatives of the middle class of nomadic society.
 The age of women who were buried with axes is determined to be between 20 and 35 years old. This means that we are talking about the most active members of military units.
 Only ordinary iron axes were found in women’s graves, usually in sets with other weapons, mainly arrows. Gala and artistically decorated pick axes or sceptre axes, which served as symbols of high social status and power, are not known in women’s graves.
 Axes from women’s graves typologically and chronologically do not differ from those found in men’s graves.
 
 Therefore, iron axes from women’s graves, along with other types of weapons, were obviously used for their intended purpose. They were not part of the insignia of power but marked the belonging of women to the military state.

OPTIMALISASI PRODUKSI KERIPIK TALAS DAN KERIPIK PISANG DI DUKUH CEKEL JETIS SAPTOSARI GUNUNG KIDUL

The Community Partnership Program has a targeted community of Cekel artisans of taro chips and banana chips. The partners involved are banana chip business actors (Cakrawala All-Business Cooperative) and taro chips business (Zahra) in Cekel, Jetis Saptosari Gunung Kidul. The problems found in partners are slicing fried foods for too long and not optimal, banana mixes are not safe, knowledge of product variations is limited. The solution that can be done is product management counseling that will ensure the quality of handling banana chips and taro chips products. The provision of production equipment assistance will facilitate and speed up work so as to increase productivity. Taro stripping using a double blade, plowing using a chopper machine, slicing using a spinner. Production increased, sales increased. Increased production and sales will improve well-being. Increased insight and additional knowledge of diversification of processed banana, cassava, and peanut products. There is a transfer of technological innovations so as to increase the pace of production, product quality and work safety. There is an increase in the production rate occurring in the slicing process which originally took 30 minutes to 2 to 3 minutes. The improvement of product quality occurs by draining the oil of natural slicing residue using a spinner. Work safety is improved by avoiding oil splashes on the hands during banana plowing

Experimental investigation on pressure fluctuation characteristics of a mixed-flow pump as turbine at turbine and runaway conditions

The pump as turbine (PAT) converts water energy into electricity energy, which greatly accelerates the construction of new power system. However, in the actual use of pump as turbine, its complex internal flow usually causes high-amplitude pressure pulsation, which seriously affects the operation efficiency of the PAT. The investigation on pressure-pulsation characteristics of a mixed-flow pump at turbine and runaway conditions is carried out in an open test rig, and the frequency domain characteristics of the pressure pulsation are analyzed based on FFT (Fourier Frequency Transform). The results show that, at the turbine mode, when the flow rate is greater than 0.8Q, the pressure fluctuation amplitude is almost three times that under small flow condition. Furthermore, when the flow rate is greater than 0.9Q, the shaft frequency and blade passing frequency occupy the dominant and secondary frequency positions in terms of the pressure fluctuation at the inlet of the volute, respectively. Moreover, when the flow rate is greater than 0.9Q, the pressure amplitude of the high-frequency component in the second section of the volute is very high, and the pulsation amplitude under a high flow rate condition is almost three to four times that under a low flow rate condition. The above phenomena show that the mixed-flow PAT is more suitable for operation under the flow rate conditions of 0.7Q and 0.8Q. In addition, at the runaway condition, when the head increases to 5.8 m, the pulsation amplitude at 7 times the shaft frequency increases significantly, which is almost 3.7 times that at the first two head conditions. The pressure pulsation which ranges from the double blade passing frequency to the triple blade passing frequency is significantly intensified, and the amplitude of the pressure pulsation at 7 times the shaft frequency is almost 3.7 times that at 3.75 m and 4.9 m.

Feasibility Study of Production of Double Blade Grass Cutting Machine

Most breeders generally feed their livestock only with grass, but for the grass itself it will be food that is easily found and is mostly given to livestock. However, most people still use machetes or sickles to cultivate grass, therefore SMEs have emerged in dealing with grass processing. The tool made is a grass chopper machine, the machine that was created also has several variations, one of which is a double knife chopper machine made by one of the students of the Nusa Cendana University Kupang, namely Stenly Naitboho. Therefore, this research was conducted to assess the performance of the chopper machine based on a feasibility study, in terms of the percentage length of the chopped material and the consumption of fuel used along with the production costs of this tool. In completing this research, several methods are needed to launch it, namely literature study and observation. After using the method used, the results of the chopping can be found, namely the percentage of the length of the chopped material measuring < 5 cm (W1) obtained an average of 54.62%, while the average percentage of the length of the chopped material measuring > 5 cm (W2) is 45.28%. For the size of the good chopped results is 2-5 cm in accordance with SNI 7785.1:2003 concerning the requirements for the results of the forage chopping machine. Another result in this study is the consumption of fuel used during the census obtained an average of 0.6 /hour. Based on SNI 7580:2013 the requirements for chopper work for fuel consumption of this machine are in category A. Production costs are obtained at a price of Rp. 4,122,200/ unit. 
 Keywords:Consumption, Fuel, Shredded, Production

Manufacturing process and experimental study of a small scale archimedes hydro powerplant by varying the number of blade

This study investigated the optimum value of Archimedes Screw Turbine (AST) performance by taking into account blades number. This paper also addressed the design approach based on a fixed incline angle of 30°, where this paper also addressed the design approach. Variations of the single and double blades were experimentally carried out concerning the turbine power output, torque, and rotation speed. This study's aim was related to the optimum power output between two blade variations, while the manufacturing and design steps were addressed as well. In the design process, the obtained blade length dimension was 0.180 m and 0.269 m for the single and double blades. Furthermore, the overall turbine's length was 1.7m, and the inner and outer of the turbine's radius were 0.069m and 0.128m. Meanwhile, the manufacturing process began with turbine modeling, plate cutting, plate withdrawal (thread formation), welding, and attained finishing process. Based on the experimental result, a double blade turbine generated turbine power by 48.8W at an average rotational speed of 115.3 rpm. Moreover, a single blade turbine produced 37.5W with turbine power averaging a rotational speed of 109.8 rpm. It was obtained that the values of turbine efficiency were 42% and 38% for double and single turbine types, respectively. Based on this finding, it can be suggested that a double blade was more efficient than a single one. This study is beneficial for the design consideration of the AST system.

Improved Savonius double blade performance using modified blade shaped with variations of the wind flow ratios on the blade inlet and outlet side

The Savonius turbine is a wind turbine that has a vertical shaft parallel to the turbine blade and has advantages that can save wind energy from all directions at low speeds. The purpose of this study is to examine the Savonius turbine model with variation in the ratio of the blade inlet side and the blade outlet side to improve turbine performance. The research method used is turbine research; conduct an experimental test by varying the ratio of the inlet and outlet sides of the blade (1:1 and 1:2) to the speed of the blade’s wind flow. Then conduct turbine performance analysis to get the best efficiency between the ratio of the inlet and outlet sides of the blade. The test was carried out at wind speeds of 5 m/s, 7 m/s, 9 m/s, 10 m/s, and 12 m/s with lamp loads distributed between 5-40 Watts. Analysis of turbine performance test The test results show that Savonius single blade wind turbine has the best efficiency of 8.43% at 5 m/s wind speed and is able to produce electricity of 10 Watts and then the best efficiency released by a 1:2 double blade wind turbine that has efficiency by 6, 9% at a load of 20 Watt and a 1:1 double blade wind turbine which has an efficiency 4.37% at a load 10 Watt.

Experimental assessment of the performance of vitreous cutters with fluids with different rheological properties.

To assess the influence of rheological properties of an artificial vitreous (AV) on the performance of double-blade (DB) and single-blade (SB) guillotine vitreous cutters, with 23-, 25-, and 27-gauge (G) probes. We evaluate the aspiration flow rate, using an optical method, based on image processing. Experiments are conducted using ten viscoelastic vitreous phantoms, with different properties that are measured with rheological tests. Aspiration rate strongly varies with fluid properties. Regardless of cutter geometry and operational conditions, the flow rate significantly decreases as vitreous viscosity and elasticity increase. All tested vitreous probes are very sensitive to changes in fluid rheology. SB cutters produce smaller flow rates compared with DB ones of the same caliber; however, they are less sensitive to fluid properties at low aspiration pressures. The use of vitreous substitutes for test performance guarantees comparability between flow rate results achieved with different vitrectomy systems operating in different media. This outcome is further confirmed by the low values of estimated flow rate relative errors.

The Controversies Surrounding Tocilizumab Administration Following Pathogen-Associated Molecular Pattern (PAMP) Induced by COVID-19

A new corona virus disease (COVID-19) has affected more than 17 million people worldwide so far, and has become a global pandemic. Since there is no definitive cure for this life threatening disease, many clinical studies are in progress in this regard. Pathogen-associated molecular patterns (PAMP) prompting by coronavirus seems to generate cellular, structural, and functional derangements induced by immune dysregulation as well as many biological abnormalities including cytokine storm. The role of IL-6 in viral pneumonia and also its inhibition impact on the prevention of organ damage are still unknown.IL-6 seems to behave as a double blade evil cytokine, by playing a valuable role in cell to cell natural physiological communication. Tocilizumab, as an inhibitor of interleukin (IL)-6, may interrupt the paracrine system while causing dissemination of bacterial, fungal, and other viral infections, especially COVID-19, who are at a high-risk for development of sepsis and life-threatening superinfection.

Clinical and patient-centered outcomes using two types of subepithelial connective tissue grafts: A split-mouth randomized clinical trial.

This split-mouth randomized clinical trial compared two different types of subepithelial connective tissue grafts (SCTG) considering clinical parameters and patient-centered outcomes in patients with bilateral recession type 1 multiple gingival recessions after 6 months postoperatively. A total of 21 patients were surgically treated with coronally advanced flap (CAF) associated with SCTG harvested by: double blade scalpel (DBS) and de-epithelialized (DE) SCTG. Periodontal clinical parameters and esthetics were evaluated by a calibrated periodontist at baseline and after 6 months. Patient-centered outcomes related to pain/discomfort and esthetics were assessed with visual analogue scale after 7 days and 6 months, respectively. All clinical parameters, with the exception of probing depth, demonstrated differences in intragroup evaluation, comparing baseline to 6-month evaluation (P<0.05). Both groups presented reduction of recession depth and recession width and gain of keratinized tissue thickness, keratinized tissue width, and clinical attachment level (P<0.05). Intergroup comparison (DBS × DE) demonstrated no significant differences considering clinical parameters and periods. Both techniques improved esthetics evaluated by patients, without a difference between groups in patients and professional analysis. However, DBS group presented inferior pain/discomfort compared with DE (P<0.05). DBS and DE associated with CAF presented satisfactory clinical outcomes. However, DBS presented inferior morbidity, an important fact for decision-making process.

Performance of Double Blade Savonius Rotor at Low Rotational Speed

The performance of the single and double blade Savonius rotors are numerically analyzed using the K-ε/realizable turbulence model. The computations are implemented at different values of tipspeed ratio from 0.2 to 0.4 with a step of 0.05. Both rotors have the same dimensions with an external overlap between their blades equals 0.02 m. The results indicate that the double blade rotor performs better than the single blade rotor in terms of power coefficient. In addition, the torque coefficient is improved at all tested values of tip-speed ratio. Furthermore, the results of the simulation show that the maximum power coefficient was 0.163 at tip-speed ratio = 0.4 for the double blade rotor, whereas the maximum improvement of the double blade rotor occurs at tipspeed ratio = 0.2 with a percentage of 11.86% compared to the single blade rotor. Moreover, the highest value of the torque coefficient was 0.524 at tip-speed ratio = 0.2 for the double blade rotor.

Al6061 Reinforced Al2O3 Metal Matrix Composite Produced by Double Blade Stir Casting

Demand for materials with excellent mechanical properties and lightweight increase in a recent year especially for high-performance applications. Aluminum reinforced Al2O3 composite (AMC) provide this superior property. Therefore in this research, aluminum alloy 6061 was used as a matrix and Al2O3 with 10 and 15 Vf-% as a reinforced for making metal matrix composites while magnesium as a wetting agent was used various from 8, 10 to 15 wt-% to improve the wettability between Al and Al2O3 since aluminum was poor wetting with ceramic. Al alloy 6061 was melted at 800 oC and magnesium was added into Al molten, then Al2O3 particles were poured into the melt. The process using double stirrer with a rotational speed of 1000 rpm for 3 minutes to distribute all Al2O3 particles in the Al melt and all the gas bubble formed was removed by flushing an Argon for 2 minutes. The composites produced then characterized both mechanical properties and microstructural analysis. The focus of this research is to investigate the effect of Al2O3 and Mg on the mechanical properties of composites. The result showed that the optimum tensile strength was 202 MPa which was obtained in composite with 10% Vf-% Al2O3 and 10 wt-% Mg. Moreover, hardness and wear resistant to composite increased with the addition of Al2O3 and Mg content due to good wetting in composites with 10 wt-% Mg. The double blade stirrer has contributed to the random distribution of Al2O3 particles in the molten Al. The microstructure observations showed that the composites yield pores and impaired the mechanical properties of composites.

Numerical simulation and application of noise for high-power wind turbines with double blades based on large eddy simulation model

The rapid development of the wind turbine industry has brought with it increasingly serious environmental problems regarding noise generated by turbines. Therefore, wind turbine noise has become an important research topic to solve the larger issue of environmental noise. Using computational fluid dynamics software and a large eddy simulation turbulence model, the aerodynamic noise created by a 3.0-MW high-power double blade is calculated using the FW-H acoustic model. The discrete characteristics of the tip noise spectrum are determined according to the static pressure and flow field distribution of the double blade. Based on the IEC standard, a monitoring point is selected as the noise-testing index of the fan, and the sound pressure level at this point is determined. The most appropriate location to install the wind turbine is determined based on restrictions on the decibel levels for wind farms. This method can be used not only to study the aeroacoustic characteristics of the blade, but also for guidance regarding the suitable noise level in the installation area of the wind turbines.

Tomato’s Mechanical Properties Measurement Aiming for Auto-harvesting

Freshly-eating tomato’s auto-harvesting is urgently needed to replace labor-costly manual harvesting. And a feasible picking end-effector is a key part for mechanical harvesting, as the irregular-sized and soft fruits should be reliably separated from the plant. In this paper, the mechanical properties of “Jiali 14” tomato was measured and analysed to support the design of picking end-effector. The methods and devices for measuring a series of force parameters were researched, including fruit/stalk friction coefficient, fruit pressure resistance, stalk cutting force, and abscission-layer breakage force. Through measuring the pressure and maximum static-friction force between the fruit/stalk and the contrast material, the friction coefficients between fruit/stalk and stainless steel, PVC and rubber was calculated. The pressure resistance of fruit also was evaluated by measuring the extreme pressure on the test samples, and the influences from the fruit’s maturity and the pressure direction also were analysed. The stalk cutting force, with the single and double blade, both was measured and compared. The breakage force of the calyx abscission-layer and the tie abscission-layer also was measured, and the force value variation with its anisotropy and the fruit maturity was analysed. The measurement and analysis result in this paper was supposed as a necessary reference for developing the tomato’s auto-harvesting machine.

The design and kinetostatic modeling of 3PPR planar compliant parallel mechanism based on compliance matrix method.

Compliant Parallel Mechanisms (CPMs) are widely used in micro/nano-positioning systems. In recent years, CPMs with a large travel range (≥1 mm) have been getting increasing attention. In this paper, a 3 Prismatic-Prismatic-Revolute (3PPR) planar CPM with a motion range of 5 mm × 5 mm × 5° is designed. The mechanical structure is characterized by the application of three joints based on a compliant four-bar mechanism, which guarantees the motions along/about the specific axes to improve motion accuracy. A double blade rotary pivot is served as a revolute joint to decrease the drift of pivot and produce a large rotation range without loss of compactness. The compliance matrix method is implemented to kinetostatic modeling, and the input coupling effect, which is always neglected or modeled complicatedly in 3-Degree-of-Freedom planar CPMs, is involved with the principle of superposition. The feasibility of the mechanical design and the accuracy of the developed kinetostatic model are validated by finite element analysis and experiments, respectively. The results indicate that the modeling method based on the compliance matrix method is concise, effective, and accurate, and can be extended to other more complicated CPMs.

A Comparative Study on Bronze Age Stone Tool Assemblages between the Northeastern China and Korean Peninsula

먼저 남한지역 미사리유형의 석기와 북한지역 청동기시대 초기 자료를 비교하면, 가장 이른 단계의 석검 부재, 단면 편평형과 오목형 삼각만입촉의 공반, 장방형&#8228;어형&#8228;즐형&#8228;제형 양인 석도의 공존, 단면 편평형 중심의 양인 석부, 무공석도, 동북형석도, 부리형석기 등을 볼 때 압록강 및 두만강유역 석기와의 공통점이 관찰된다. 이 중 석검의 부재는 압록강유역, 동북형석도와 부리형석기의 출토는 두만강유역의 특징이다. 이와 달리 양인 석도는 압록강 상류와 두만강유역에 주로 분포하며, 무공석도 역시 해당 지역의 특징적 형식 중 하나이다. 따라서 보다 구체적으로 압록강 상류～두만강유역을 미사리유형과 관련된 지역으로 상정할 수 있다. 이러한 양상을 중국 동북의 지역별 석기상과 비교하면, 遼東山地와의 유사성을 지적하는 것이 가능하다. 석검의 부재, 단면 편평형과 오목형 삼각촉의 공반, 장방형 양인 석도의 존재, 단면 편평형 양인 석부의 높은 점유율, 편평편인석부와 석착, 무공석도, 환석 등이 모두 미사리유형과 공통하는 석기 양상들이다. 물론 다른 지역에서도 이 중 몇몇 요소들이 관찰되고 있지만, 전체적으로 볼 때 가장 유사한 것은 역시 遼東山地라 할 수 있다. 따라서 석기상으로 보는 한 남한지역의 미사리유형은 遼東山地 馬城子 문화로부터 기원하여 압록강 상류～두만강유역을 거쳐 남하하였을 가능성이 높다고 판단된다.A Comparative analysis between Bronze Age stone tool assemblages of Misari-type in South Korea and North Korea with those of the Aprok river and the Tumen river reveals some commonalities including absence of the earliest stone dagger, coupled presence of flat crosssectioned and concave triangler shaped arrowheads, co-presence of rectangular, convex, lenticular and trapezoid shaped double blade knives, a double blade stone axe with a flat cross-section, an unperforated stone knife, a northeastern type stone knife, and a peak shaped stone tool. Absence of stone dagger is the characteristic of the Aprok river region’s stone assemblage, but a northeastern type stone knife and a peak shaped stone tool are that of the Tumen river region’s stone assemblage. A double blade knife is dominantly present in the upper reach of the Aprok river and the Tumen river regions. An unperforated stone knife is typical of these regions’ stone assemblage. Thus more specifically, the upper reach of the Aprok river and the Tumen river region can be said to be related to the Misari type stone tool assemblage. A comparison on stone tool assemblages between Korean Peninsula and Northeastern China indicates that the Misari type is quite similar with the Liaodong mountain region. The common features of them include absence of a dagger, coupled presence of a flat cross-sectioned and concave triangler shaped arrowheads, presence of a rectangular shaped double blade knife, the higher frequency of double blade axe with a flat cross-section, a single blade axe with a flat cross-section, a stone chisel, a round stone. Although some components are present in other regions’ stone assemblages, the degree of similarity with the Misari type is the highest in the Liaodong mountain region’s stone tool assemblage. Thus the Misari type in South Korea was likely originated from the Liaodong mountain region Machengzi Culture and had spread southward through the upper reach of the Aprok river and the Tumen river regions in terms of stone tool assemblage.

Fluidics of Single and Double Blade Guillotine Vitrectomy Probes in Balanced Salt Solution and Artificial Vitreous.

PurposeTo assess the fluidics of double-vitreous cutter blade (DB) compared with single-blade (SB) guillotine with 23-, 25-, and 27-gauge vitrectomy probes. To assess flow characteristics and flow rates in viscous and viscoelastic fluids.MethodsWe used Particle Image Velocimetry to measure the flow field close to the tip of each cutter probe and we derived kinematic quantities of interest, such as kinetic energy and acceleration. We performed measurements both on a balanced salt solution (BSS) and on a viscoelastic artificial vitreous (AV).ResultsThe flow rate is significantly higher with DB than SB vitrectomy probes, for a given pumping pressure and cutting rate. The fluid flow observed is very different between BSS and AV tests.ConclusionsThe DB has more efficient fluidics than SB vitrectomy probe in all tested conditions. Fluid acceleration depends on the cutting frequency, especially in the case of measurements in AV. The flow rate strongly depends on the pressure and it is little affected by the cutting frequency, in a range of clinical interest. The 27-G DB produces flow rates similar to the 23- and 25-G SB, with significantly smaller acceleration. The flow induced in the AV is different from that in BSS and oscillates at different frequencies.Translational RelevanceDB cutters prove to be more efficient in terms of lower acceleration for a given flow rate. The latter is mainly controlled by aspiration pressure and less by cut rates. The influence of vitreous rheology deserves further investigations.