Lift Positions Research Articles

Experimental study of hydraulic lifting platform based on multi-ring disc magnetorheological valve

To enhance the operational capabilities of a hydraulic lifting apparatus, a hydraulic lifting platform was engineered based on a multi-ring disc magnetorheological valve. The pressure drop characteristics of the multi-ring disc magnetorheological valve were determined through theoretical analysis, supplemented by magnetic field simulations to assess its performance. The effects of different currents on the stability and response time of the hydraulic lifting platform are studied, and the control accuracy of the hydraulic lifting platform position is verified. The results show that the saturation current of the magnetorheological valve is 2.5 A. The addition of current to the magnetorheological valve leads to a rapid increase in both actuator speed and acceleration, which then levels off. Similarly, the response time of the actuator decreases with an increasing current until it stabilizes. At a coil current of 1.5 A, the actuator achieves a speed of approximately 86 mm s−1, an acceleration of approximately 105 mm s−2, and a response time of approximately 7.15 s. Furthermore, the lifting position accuracy of the hydraulic lifting platform is ±1 mm.

Comparing Video Analysis to Computerized Detection of Limb Position for the Diagnosis of Movement Control during Back Squat Exercise with Overload.

Incorrect limb position while lifting heavy weights might compromise athlete success during weightlifting performance, similar to the way that it increases the risk of muscle injuries during resistance exercises, regardless of the individual's level of experience. However, practitioners might not have the necessary background knowledge for self-supervision of limb position and adjustment of the lifting position when improper movement occurs. Therefore, the computerized analysis of movement patterns might assist people in detecting changes in limb position during exercises with different loads or enhance the analysis of an observer with expertise in weightlifting exercises. In this study, hidden Markov models (HMMs) were employed to automate the detection of joint position and barbell trajectory during back squat exercises. Ten volunteers performed three lift movements each with a 0, 50, and 75% load based on body weight. A smartphone was used to record the movements in the sagittal plane, providing information for the analysis of variance and identifying significant position changes by video analysis (p < 0.05). Data from individuals performing the same movements with no added weight load were used to train the HMMs to identify changes in the pattern. A comparison of HMMs and human experts revealed between 40% and 90% agreement, indicating the reliability of HMMs for identifying changes in the control of movements with added weight load. In addition, the results highlighted that HMMs can detect changes imperceptible to the human visual analysis.

Flow analysis of a control ball valve in a common rail fuel injector

The electronic control common rail fuel injection system is one of the key technologies being used in modern diesel engines to improve the engine performance. A numerical simulation was conducted to study the characteristics of the fuel flow around the ball valve in the common rail fuel injector. The lift of the control ball valve and static pressure of the flow field around the control ball valve were measured respectively. The simulation was performed with the measurements as boundary conditions such that the flow characteristics can be correlated with the valve lift and the pressure upstream of the ball valve. Simulation results showed that during the valve opening and closing, a high pressure area appeared below the ball valve, while cavitation appeared in the area around the control ball valve. Specifically, the cavitation mainly appeared around the sealing circle, and its upstream area and the conical surface from the entrance to a certain distance downstream. The flow throttling happened at the outlet orifice under the steady-state condition when the valve was at the maximum opening position. The cavitation around the control ball valve was more serious under higher rail pressure conditions. The formation and development of the cavitation was found to be depending on the lift position of the ball valve and pressure of the flow around the ball valve during the valve opening and valve closing. Higher value of void fraction appeared in the flow when the lift of the ball valve was at a larger opening position. It was found that cavitation around the ball valve will affect the consistency and stability of the fuel flow. And cavitation erosion found at the valve seat from a simplified durability test appeared to be close to the place where cavitation appeared from simulation. Therefore, it is suggested that simulation work can be used to examine if cavitation occurs in the flow path of the control ball valve inside the injector in design phase and make necessary changes on the design to prevent the cavitation and the resulting damages to the control ball valve in the injector.

IDENTIFIKASI FAKTOR RISIKO KEJADIAN LOW BACK PAIN PADA PEKERJA INDUSTRI KATERING

Background: Low back pain is pain that is felt in the affected anatomical area with various variations in the duration of pain. This pain is felt in the lumbar or lumbo-sacral region. Occupational diseases caused by non-ergonomic conditions include musculoskeletal disorders. Food industry workers are at risk of low back pain due to their activities such as bending, lifting and carrying heavy loads for a long time and repetitively. The purpose of this systematic review is to determine the relationship of position and length of work of ketring business workers to the incidence of LBP. Methods: searches are conducted through Google Scholars, PubMed, Cochrane Library, ResearchGate and Science Direct. Obtained 30 journals that contain the topic of low back pain in catering industry workers. Results: from 30 journals, 12 cross-sectional studies, 7 systematic Reviews, 4 literature reviews, 5 cohort studies, 1 meta-analysis, and 1 case-control study were obtained. Discussion: LBP occurs due to the biomechanics of the lumbar vertebrae due to changes in body weight points with compensation for changes in body position and will cause pain. Muscle strain and spinal ligament sprain are among the main causes of LBP. lifting positions that are less ergonomic and repetitive in the long term are causing complaints of low back pain in ketring workers. Conclusion: the risk factors for low back Pain (LBP) in workers in the mining industry are caused by several factors such as position and posture when working which tend to be static and repetitive, old age workers, workers with excess weight. Keywords: Risk factor, LBP, worker, kitchen, catering

Investigation on the time/frequency domain prediction model of radiation noise based on the source map

The main exterior noise sources of the high-speed train CRH380AM, such as pantograph and bogie, are studied by using the field test sound imaging data, and the equivalent point source spectrums are obtained here. Then, the prediction model of the exterior train noise is presented by using the moving point sound source radiation model in the time/frequency domain. The correctness and effectiveness of the model are verified by the field test data. The radiation contribution of local noise sources is analyzed by using this model, and the following conclusions are obtained: The largest noise sources are in the bogie areas, which provide the radiation contribution rate of about 80% when the train speed is above 300 km/h. The variation of the maximum radiation noise level can be ignored when the train formation or the pantograph lifting position is changed. The model can evaluate the radiated noise of similar vehicles quickly and accurately, which provides technical reference for acoustic optimization design of high-speed train.

Can we enable individuals to reach further down without rounding their backs before beginning a lift? Examining the influence of starting foot and trunk position on reach depth

There is disagreement regarding the efficacy of ‘safe’ lifting recommendations for reducing low back disorder risk. These recommendations commonly focus on minimising lumbar spine flexion, which limits the range of allowable starting lift positions for that person. This study evaluated whether starting postural adaptations could allow a person to reach down further without rounding their lumbar spine before beginning a lift. Reach displacement was measured as participants performed a series of maximal reach tasks under different combinations of stance width, foot orientation and trunk inclination, with their lumbar spine motion restricted. There were no interactions between any of the three postural adaptations or any effect of stance width or trunk inclination. Seventy-nine percent of participants achieved their greatest reach displacement with their feet externally rotated, which contributed to a 4 cm greater reach displacement compared to a neutral foot orientation (p < 0.001). Practitioner summary: This study examined whether aspects of initial posture could influence the ability to adhere to ‘safe’ lifting recommendations across a range of lift heights. As a component of lifting (re)training interventions, practitioners should consider starting lift posture adaptations (e.g. manipulating foot external rotation) to improve capacity to adhere to recommendations.

Study on Capture Efficiency of Particle Trap and Performance Improvement Method for DC GIL/GIS

Whether the metal particles in DC GIL/GIS can be effectively captured by particle traps affects its safety and stability operation. In this paper, a test platform simulation of the real structure is set up to study the influence law of the particle trap on the capture rate. The effect of the key structure parameters and shielding balls on the capture rate of the up-lift particle trap is studied, and a surface coating strategy on the particle trap is proposed to improve the trapping efficiency of the trap. The results show that increasing the length and height of the trap can improve the capture efficiency of the particle, while a too-large or too-small grid is not conducive to trap capture. With the initial lifting position of the particle away from the particle trap, the capture rate decreases. The cone-shaped structure is conducive to the particles moving toward the trap direction and the hollow structure had the trapping efficiency of the particles. The research observations also indicate that the shielding balls with cone-shaped outside and hollow inside can improve the capture rate of the particle trap by 37.2% on average. Furthermore, it is found that the surface coating of the particle trap can isolate the charge transfer when moving particles arrive, which can increase the capture rate of the particle trap by 17.2% on average. Accordingly, typical trajectories of particles captured and escaped are analyzed and discussed. This work provides a significant idea to design the particle traps and the controlling strategies of DC GIL/GIS particle pollution.

Sequential matching optimization for lifting trajectory and ballast water allocation of the intelligent revolving floating crane

Revolving floating crane (RFC) is one of the core equipment applied to major offshore lifting operations due to its strong working ability. Its operation safety is directly determined by the collaborative matching between the lifting trajectory and the ballast water allocation. However, such matches are accomplished manually in the actual operations, leading to low efficiency, high energy consumption, etc. To address these problems, the unattended intelligent operation mode is an inevitable solution for the RFC. Therefore, a novel sequential matching optimization (SMO) method for the lifting trajectory and the ballast water allocation of the RFC is proposed in this study. The SMO method is proposed based on the point to point (PTP) method and the corresponding principles are firstly explained in great detail. Then, the SMO model is established for searching the optimal scheme with the lowest energy consumption of the lifting and ballast systems. Furthermore, to explore the corresponding superiority, the proposed SMO method is compared with the conventional method, finding that the proposed SMO method can perfectly achieve better lifting performances. Finally, numerical experiments regarding different lifting positions, crane loads, and quantities of the ballast tanks are performed to verify the feasibility of the SMO method.

PERANCANGAN ALAT PENGANGKUT MATERIAL GEROBAK SORONG YANG ERGONOMIS UNTUK EFISIENSI DAN PENINGKATAN PRODUKTIVITAS

The development of an industrial product arises with various problems and product quality that has high value. One example of a product that needs to be redesigned is a wheelbarrow or handcart. The wheelbarrow is a simple material conveyance which is pushed by hand, one wheel and one operator through the handle. This research aims at an ergonomic and economical handcart, so as to produce a product that can be useful for medium-sized industries and can increase efficiency and increase work productivity. This research was carried out by redesigning the product as a development, where this product is usually used in a building called a traditional material conveying tool, then calculating the axle and pedal stress on a wheelbarrow. In this study it can be concluded that the wheelbarrow or wheelbarrow is designed more ergonomically with several changes including changes in the height of the stalk from the ground to minimize bending when lifting the wheelbarrow, changes in shape and size of the supports to accommodate various lifting positions, other things, changes in shape and the size of the body so that when lifting and pushing the wheelbarrow, the load is more balanced, the addition of a jack to make it easier for users to spill loads from the body, the addition of two rear wheels to make it easier to push the wheelbarrow, and change the handle to make it easier for users

Performance-maximum optimization of the intelligent lifting activities for a polar ship crane through trajectory planning

Knuckle boom crane (KBC) mounted on a polar ship (PS) is a maritime engineering equipment widely used in offshore activities. The working performance of a PS-mounted KBC (PSKBC) may degrade quickly if manipulated manually under extreme working conditions in polar region. To address the challenges, a performance-maximum optimization method through trajectory planning is developed to further promote the intelligently unmanned lifting processes of the PSKBC. Firstly, the dynamic model of lifting activities of the PSKBC is established using Lagrangian equation, based on which the point-to-point trajectory planning (PTP) method is developed for lifting processes. Subsequently, the PTP‐based optimization model is established to realize the minimum energy consumption and time cost of the lifting activities of the PSKBC, and the obtained optimal lifting performance is compared with the traditional S-curve method. To verify the superiority of the proposed performance-maximum optimization method, numerical simulations of the lifting activities of the PSKBC with respect to different crane loads and final lifting positions are performed. Results indicate that the PTP‐based performance-maximum optimization method for the PSKBC can perfectly achieve better performances with applicable lifting trajectories regarding various working conditions and demands.

Comparison of electromyography activity of abdominal muscles and hamstrings in women with low back pain during different lifting positions

Objective: back pain is one of the most common health problems in different societies of the world, especially in industrialized countries. The aim of this study was to compare the electromyography activity of abdominal muscles and hamstrings in women with low back pain in different lifting positions. Methods: The present study was a quasi-experimental and laboratory study. The statistical sample consisted of 10 women with back pain and 10 healthy women for whom using 16-channel EMG system and surface electrode, electromyography activity of the right muscles (Rectus Abdominis, Internal Abdominis, External Abdominis, and Biceps Femoris muscle and Semitendinosus) while lifting with three Squat, Stoop and freestyle methods was recorded. Data analysis was performed using SPSS software. Analysis of variance was performed by repeated measures and independent t-test at a significant level (P≤0.05). Results: In the stage of lifting weight, the Internal Abdominalis muscle, healthy individuals were more active in the squat technique than in Frees and Stoops, and the patients, Semitendinosus muscle was less active in the Free style technique than in the Squat technique, but in lowering weight Semitendinosus muscle of back-pain patients showed more activity in Free style technique. Conclusion: In the present study, Free style method in patients with back pain is a safer method for lifting the load than the other two methods. Also, for sports rehabilitation in people with back pain, special attention should be paid to the role and strengthening of the hamstring muscles so that the patient has better performance for lifting activities.

Effect of laser plasma on Nd:YAG laser drilling of acrylic plate with high optical density

Laser material processing (LMP) is used to replace traditional material processing techniques, such as material cutting, thin plate drilling, and surface processing. When a high-energy laser is projected onto a material, the temperature of the material increases rapidly, changing the characteristics of the material and making the material on the surface vaporize and peel off instantly. In this study, we developed a laser system using a Quantel Brilliant neodymium-doped yttrium aluminum garnet (Nd:YAG) with a wavelength of 1064 nm laser a pulse width of 5–6 ns, a beam diameter of the 6 mm, and 10 repetition rate (Hz) on the energy stability is within 5.60%, an F-theta lens is used to obtain a focused laser beam with a diameter of 0.2 mm. The developed system was employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate with high optical density and 7 + safe windows. A laser-safe, flat-window, visible-light-transmitting (VLT) sample was used, and the material to be drilled was a PMMA plate. The laser beam must be focused on the center of the F-theta lens and must be aligned with the distance between the F-theta lens and the linear stage. The working distance was set to 300 mm. Furthermore, the diameter was adjusted to obtain the laser plasma effect; that is, the working distance was fixed. First, the characteristics of the laser plasma and the ability of the laser to penetrate optical-grade acrylic (PMMA) plates samples were studied. By changing the lifting position of the vertical axis and varying the working distance of the acrylic (PMMA) plates, the laser beam was targeted at different positions on the acrylic (PMMA) plates. To determine the optimal parameters for the drilling process, a pulsed laser output of 174.7 mJ/pulse (3000 pulses in 5 min) was focused on the hole. Results showed that the energy was 522.98 J/cm2; a laser energy density of 141.26–275.93 J/cm2 resulted in an acceptable heat-affected zone. The Nd:YAG pulsed laser can produce laser plasma that can increase the hole diameter by up to 50% because of the produced cavity gap. Various exit and entrance hole shapes can be achieved and thus employed for different applications, such as laser beam cutting.

Study on Track Frame Model of a Thai-Made Rice Combine Harvester

A rice combine harvester has an important role in Thai rice production and has been popular in Thai farmer. AlmostThai-made rice combine harvester is too heavy and large in size. Because the track frame of Thai-made rice combine harvesteris a main component that affects the harvester’s size and weight, the objectives of this research, therefore, were to investigateand improve the track frame strength using the finite element method (FEM). Similitude analysis was employed for determiningthe proper scale of experimental frame. The strength analysis using the loading test with experimental frame was used to verifythe accuracy of the FEM. Two field-work conditions of the harvester’s header were selected namely horizontal position andmaximum lift position. The FEM results showed that the maximum stresses of those conditions were 91.13 MPa and 91.69 MPa,respectively, while the maximum deflection 2.31 mm and 2.36 mm, respectively. The experimental results from the loading testsconfirmed that the strength analysis of track frame using FEM had a high accuracy and could be applied in practical use. Theimprovement of the track frame model could increase the strength about 40% and reduce mass about 18%.

Study of Watt Governor Mechanism

Objective: The basic aim of the study is to determine the minimum, maximum speeds and sensitivity of the governor of a universal Watt governor setup available in machine dynamics laboratory in the mechanical engineering department at Jamia Millia Islamia New Delhi. Methodology: We used a tachometer to measure the spindle speed in revolution per minute. After assembling the governor setup, the author note down the initial reading of pointer on the vertical scale. After switching on the rotary switch, we slowly increase the governor speed till the sleeve is lifted from its initial position and it should be stabilized. Now, again, we increase the governor speeds in steps to get different position of sleeve lift at different rpm and noted all the observations. Findings: The actual minimum and maximum governor speeds are 211 rpm and 276 rpm respectively. The actual sensitivity of the available governor setup is 26.7 %. With the change of governor speed, the radius of rotation also changes. Novelty: This Study may be sued as simple guide lines for undergraduate / postgraduate / research scholars as well as scientist to select the suitable governor to perform the required task as per specific necessity in their research work. Keywords: Governor; rpm; Centrifugal force; sensitivity; fly balls

APPLICATION OF JOB SAFETY ANALYSIS (JSA) METHOD IN IDENTIFYING THE RISK OF WORK ACCIDENTS IN CHARGED MANPOWER IN BUNGKUTOKO PORT, KENDARI CITY

Background: Data from the Ministry of Manpower of the Republic of Indonesia that the number of work accidents in Indonesia in 2016 was 101,368, in 2017 there were 123,041 cases, in 2018 there were 173,415 cases. At the end of September 2019 there were 130,923 cases and there were 6 people who died every day. On September 2019, the sectors that contributed to the relatively large number of work accidents were the processing industry with 50,358 (38.46%) cases, trade of 9,559 (7.30%) cases, transportation and warehousing 2,694 (2.06%) cases, and the rest 68,312 (52.18%) cases from other sectors. The same thing was reported by the Social Security Administration for Employment that there was an increase in work accidents by 40%, from 157,313 in 2018 to 173,105 cases in 2019. Methods: This research is quantitative research with a descriptive analytic research design and applied observational analytic approach. The population of all loading and unloading workers was 150 people divi ded into 3 teams, where each team consisted of 50 TKBM members of Bungkutoko Port, Kendari City. Result: This study found 3 work stages with the highest RPN value, namely, wrong in the lifting position in the stevedore of work process at the time workers lift goods and put them into the net, as well as in the cargodore of work process when workers stack goods on the truck with a value of 288, stumbling (cargo) which occurs in the stevedoring work process where The worker on the truck directs the crane and the net into the truck body with an RPN value of 192, and pinched by a lifting tool in the cargodore of work process when workers remove goods from the sling on the truck / remove the sling, with a value of RPN 144. Conclusion: There were 3 loading and unloading work processes, namely, stevedoring, cargodoring, and delivery with each work stage having potential hazards, the impact of hazards, and control efforts, and the person in charge of control efforts.

Effects of injection pressure and length-diameter ratio on the velocity and cavitation inside injector nozzle

Computational investigation was conducted to understand the effects of various parameters on nozzle flow and cavitation in a diesel fuel injector for a diesel engine. The effects of injector parameters were simulated for different conditions including the injection pressure, the outlet pressure, the position of the needle lift, and the length of the nozzle. Results show that some parameters have obvious influence on cavitation associated with nozzle flow. When the outlet pressure was constant, the velocity through the nozzle increased with the injection pressure, resulting in the cavitation at the injection pressure over 120 MPa. When the injection pressure was constant, the velocity inside nozzle decreased with the outlet pressure. As the needle tip moved closer to the bottom of minisac, the velocity inside nozzle decreased and the cavitation did not take place. The length of the nozzle hole had little effect on the velocity at inlet, but it affected the velocity distribution at outlet.

The Analysis of Employees’ Work Posture by using Rapid Entire Body Assessment (REBA) and Rapid Upper Limb Assessment (RULA)

This study aims to analyze the work posture of employees by using Rapid Entire Body Assessment (REBA) and Rapid Upper Limb Assessment (RULA) methods. In this study, the angle of the employee was calculated, and the results showed that on the body part B, the angle of the back movement is 77º flexion, the neck is 18º extension, and the leg is 39º, while the leg is not uniformly supported. One of the body parts, such as the upper arm is formed an angle of 65 ° flexion, the forearm is 13 ° flexion, the wrist is 0 ° flexion, and the wrist is in the intermediate range of rotation. Based on the results of RULA, a grand score is 7, categorized as Action level 4. Meanwhile, based on the results of REBA, the grand score obtained is 11, and also categorized as Action level 4. Based on the calculation of work posture using RULA and REBA methods, it revealed that the operator’s work posture has a high-level and dangerous risk. Therefore, the operator needs to immediately improve his work posture. In addition, due to the lifting position that was started with no squatting position, it causes waist injures, since it becomes the lift’s pedestal.

Flexed lumbar spine postures are associated with greater strength and efficiency than lordotic postures during a maximal lift in pain-free individuals

BackgroundInspite of common lifting advice to maintain a lordotic posture, there is debate regarding optimal lumbar spine posture during lifting. To date, the influence of lumbar posture on trunk muscle recruitment, strength and efficiency during high intensity lifting has not been fully explored. Research questionHow do differences in lumbar posture influence trunk extensor strength (moment), trunk muscle activity, and neuromuscular efficiency during maximal lifting? MethodsTwenty-six healthy participants adopted three lumbar postures (maximal extension (lordotic), mid-range (flat-back), and fully flexed) in a free lifting position. Motion analysis and force measurements were used to determine the back extensor, hip and knee moments. Surface electromyography (EMG) of three trunk extensors and the internal obliques were recorded. Neuromuscular efficiency (NME) was expressed as a ratio of normalised extensor moment to normalised EMG. ResultsSignificantly higher back extensor moments were exerted when moving from an extended to mid-range, and from a mid-range to fully flexed lumbar posture. This was accompanied by a decrease in activity across all three back extensor muscles (P < 0.001) resulting in a higher NME of these muscles in more flexed postures. Change in lumbar posture did not influence hip or knee moments or internal oblique activation. SignificanceA flexed-back posture is associated with increased strength and efficiency of the back muscles compared to a lordotic posture. These findings further question the manual handling advice to lift with a lordotic lumbar spine.

Analisis Posisi Optimal Pengangkatan Balok U-Shell Dengan Menggunakan Crane

Riau University Education Hospital was built to support lectures and as a tool in research in the field of health. Teaching Hospital was built using U-Shell precast blocks with consideration of time and cost efficiency in project implementation. U-Shell beams are made at the project site and the method of lifting precast beams is generally recommended from the factory. While the U-Shell beam is made at the project site, it is necessary to calculate the lifting distance so that the beam when moved does not occur due tomoment damage. U-Shell beam lifting calculation is done with several alternatives, namely the position of 1 /3L, 1 / 4L and pedestal xL. The result of the moment calculation shows the moment value for each alternative, namely in the beam with dimensions of 350 mm x 800 mm position 1 / 3L M1 of-1242 Kgm and M2 of-931.5 Kgm, at position 1 / 4L M1 of-698.63 Kgm and M2 of 0, at position 1 / 5L M1 of-478.97 Kgm and M2 of 480.64 Kgm. As for the beam with dimensions of 300 mm x 700 mm position 1 / 3L M1 of -460.8 Kgm and M2 of -345.6 Kgm, at position 1 / 4L M1 of -256.2 Kgm and M2 of 0, at position 1 / 5L M1 of - 177.7 kg and M2 of 178.32 kg. From the three alternatives we get an effective lifting position, which is 1 / 5L.

Experimental investigation on the microscopic characteristics of underexpanded transient hydrogen jets

The microscopic characteristics of hydrogen jet affect the concentration distribution and gas-air mixing of high-pressure gas jets for a hydrogen engine. In this study, the schlieren method was used to record the hydrogen jet for an outward-opening injector. The results showed that the jet asymmetricity was large in the initial stage of the jet development, then decreased rapidly as the jet developed, and finally entered a stable range of 13%–38% when the valve fully opened. The increase of the ambient pressure was beneficial to reduce the fluctuation range of the asymmetricity. The steady S of an outward-opening injector (S = 0.7 ± 0.03) is larger than that of a single-hole injector (S = 0.25 ± 0.05). The increase in injection pressure and the decrease in ambient pressure caused S to decrease to 1 faster. The steady Γ of an outward-opening injector was experimentally determined, and the value (Γ = 0.98 ± 0.1) was smaller than that of a single-hole injector. According to the transient Γ, the injection process can be divided into the developing phase and the self-similar phase. Γ increased rapidly with time and then stabilized after the injector valve reached its maximum lift position. The gas concentration distribution was uneven along the axial direction. The mole fraction decreased with the increase in axial penetration, and entered a stable range of 0.27–0.37 when axial penetration was greater than 20 mm. The average equivalent ratio was large at the beginning of injection under different pressure ratios, and then decreased and finally stabilized in the range of 1.4–5.