Lifting Heights Research Articles

Research on photovoltaic water pumping system based on valve opening model

Photovoltaic water pumping system (PVWPS) is an important way to use solar energy. In order to further improve the solar energy utilization rate of PVWPS, this study proposes a valve opening model, which solves the problem of more solar energy waste caused by fixed pipeline characteristics under different irradiation intensities. Firstly, the theoretical calculation formula of pipeline flow is deduced according to the balance relationship between photovoltaic energy supply and energy demand of water lifting pipeline in PVWPS, and its working principle is expounded. Finally, the function model of pipeline flow-valve opening-radiation intensity is derived from the cycle test of PVWPS, and the PVWPS with water lifting height of 10 m, 12 m and 14 m is verified by all-day test. Compared with the unregulated valve, the cumulative water extraction of the PVWPS with three water lifting heights after valve regulation is increased by 15.85 %, 18.06 % and 80.71 % respectively, indicating that the cumulative water extraction of the PVWPS can be effectively improved by adjusting the valve opening. This study provides a new idea for improving the utilization rate of solar energy in PVWPS.

Experimental study on strain and stress of steady device in a catenary for a high-speed railway

Steady device is an important component in a catenary for a high-speed railway. It plays an important role in ensuring the current collection quality and stable and reliable operation of the train. In this paper, the strain distributions of positioner tube, column and pin sleeve in the positioning device are measured by strain gauges in our laboratory, and the variation laws of axial and transverse strains, and axial stresses of the three key components under different horizontal and oblique loads, and lifting heights of positioner are studied and analyzed. It is found that the strains and axial stresses of all measuring points basically have a linear relationship with the horizontal load, which are little affected by the oblique load. There is an ‘arch’ change law between these strains/stresses and the lifting height of positioner. For the stresses of two measuring points at the same section, the tensile stress is generally higher than the compressive stress. The maximum tensile stress occurs on positioner tube, which is the weakest part. This work provides the technical support for the material selection, structural design and detection of the positioning device.

Effect of Probe Lifting Height in Jumping Mode AFM for Living Cell Imaging

Atomic force microscopy (AFM) is one of the effective methods for imaging the morphological and physical properties of living cells in a near-physiological environment. However, several problems caused by the adhesion of living cells and extension of the cell membranes seriously affect the image quality during living cell imaging, hindering the study of living cells. In this work, jumping mode AFM imaging was used to image living cells at varied probe lifting heights to meet image quality requirements, and image quality related to the probe lifting height is discussed in detail. The jumping mode was divided into three parts based on the varying heights of the lifted probe, namely near-contact mode, half-jumping mode, and full-jumping mode, and the causes of their imaging drawbacks were analyzed. At an appropriate lifting height, the probe can be completely free from the influence of cell adhesion and self-excited oscillation, thus avoiding the occurrence of “trail” phenomena and invalid points in the imaging of living cells and improving the image quality. Additionally, this work provides a new approach to calculating the lateral force through the adhesion of trace and retrace scanning at a low height, which is important for studying the extension characteristics of the cell membrane.

Investigation of a stress-strain state of a rubber-cable rope with cables of different tensile rigidity

Purpose. Establishment of dependences for stress-strain state parameters in a rubber-cable rope with cables of different tensile rigidity and cable breakage. Research methodology. Construction and development of an algorithm for solving a model of a stress-strain state of a rubber-cable rope with ropes of different tensile rigidity and breakage of one cable by using the methods of mechanics of layered composite materials with soft and hard layers. Findings. Analytical expressions are constructed, which allow determining the main stress-strain state indicators in a rope with an odd number of cables, while the middle cable is damaged, and tensile rigidity of the middle cable is half the tensile rigidity of the other cables. Analytical dependencies are established for determining the extreme angles of rubber shear between the cables, what allows determining the most dangerous tension states of a rope with a damaged cable, which has a different rigidity from the other cables. The level of reliability of the developed algorithm for solving the model of a stress-strain state of a rubber-cable rope with cables of different rigidity is confirmed by determining the maximum tensile forces of a rope made of three cables, in which the middle cable has a tensile rigidity half that of the other two. The force distribution coefficients between cables adjacent to the damaged one are equal to 1.25 per unit load on each cable, which corresponds to the only possible case of force distribution between parallel elements under the presented conditions. Scientific novelty. The character of influence of different rigidity and damage of the reinforcing cables on the main parameters of stress-strain state in a rubber-cable rope are established. Practical significance. An algorithm for determining the stress-strain state indicators of a rubber-cable rope, which has an odd number of reinforcing cables, its middle cable is damaged, and the tensile rigidity of the middle cable is different (lower) than the rigidity of the other cables, is developed. This makes it possible to increase the operational safety of rubber-cable ropes in hoisting and transporting machines, in particular when operating at significant lifting heights, and also contributes to justifying the use of a rope design as a stay rope in capital structures.

Design Criteria for the Construction of Energy Storage Salt Cavern Considering Economic Benefits and Resource Utilization

Underground salt caverns have been widely used for oil and gas storage and have attracted increasing attention. The construction design of salt caverns is directly related to the final storage capacity, economic benefits, and resource utilization. However, due to the numerous combinations of multi-stage process parameters involved in the construction design, it is difficult to optimize them individually through indoor experiments and numerical simulations. In this regard, this paper attempts to put forward the basic principles of cavern construction design criteria with economic benefits and resource utilization as indicators. Firstly, 1258 groups of cavern construction process parameters were randomly generated under certain basic rules, including inner tube depth, outer tube depth, oil pad depth, duration, and water injection flow rate, for five direct leaching stages. Then, the cavern capacity, economic benefit, and rock salt resource utilization corresponding to these process parameters were obtained through batch processing using single-well salt cavern leaching simulation software (SSCLS). Finally, the influence laws of the distance between the inner tube and oil pad and lifting heights, and the rates of the inner tube and oil pad on the expected economic benefits and salt resource utilization, are discussed. In the actual project, it is recommended to increase the distance between the inner tube and the oil pad, increase the ratio of oil pad lifting height to duration, and use the appropriate lifting height to obtain greater expected revenue and resource utilization. This work will improve the efficiency and scientificity of cavern construction design, which is of great significance in guiding the construction and design for energy storage in salt caverns.

Potential Determinants of Manual Lifting: Validation of Ergonomic Assessment by Scoping Review Applying Meta-analysis Approach

Introduction: Despite automation, manual load lifting is unavoidable in occupations like Industry, healthcare, defence, etc. Ergonomics studies on manual lifting conducted across the globe explored few aspects of biomechanical and physiological responses. It was hypothesised that, ‘holistic ergonomics approach’ involving simultaneous recording of these responses under single study, would elucidate potential injury causing factors more effectively and results could be validated by applying meta-analysis technique of literature review. Aim: To identify the potential determinants of manual lifting by applying multivariate statistics to existing data and correlate the results with determinants as per literature review applying meta-Analysis. Materials and Methods: Clustering and principal component analysis tools of factor analysis was applied on the data obtained under the pilot study (n=11) undertaken by same authors previously on manual lifting that assessed 26 dependent parameters simultaneously for load magnitudes (10 kg, 20 kg), lifting heights (floor-knuckle, knuckle-shoulder and floorshoulder) and lifting frequencies (1lift.min-1, 4lifts.min-1). Further, extensive scoping literature review on determinants of manual load lifting was done applying text mining tool of meta-analysis technique on R software platform using 921 pubmed abstracts published between 1991 and 2018. Results: Salient findings of factor analysis corroborated with that of scoping literature review. Accordingly, dependent variable ‘Vertical Ground Reaction Force (VGRF)’ and independent variable ‘vertical height of lift’ changed most significantly during manual lifting, showing significant positive correlations. Newton’s third law of motion states that while bipedal standing/walking/running on floor, two forces (with three vector components) are acting upon a person: the force of gravity (downward force, equivalent to body weight) and the Ground Reaction Force (GRF, an equal upward force exerted by floor). However, while standing still at one place for lifting load, only the largest vector component of GRF, i.e., VGRF acts on the body (=‘body weight’+‘load magnitude’) through the vertical height of lift. Conclusion: It may be concluded that ‘vertical height of lift’ and VGRF are possible indicators of injury potential of manual lifting. However, studies on larger sample size and meta-analysis of relevant full papers instead of abstracts need to be done in future.

Research on the Decompression Effects of Shaft Explosion-Proof Door at Different Lifting Heights

To study the decompression effects of shaft explosion-proof door at different lifting heights, this paper designed the gas explosion testing system. Based on the test results, this paper made a numeric analysis of the change regularities of the shock wave overpressure when the shaft explosion-proof door was lifted at different heights. Finally, this paper determined the proper lifting height of the shaft explosion-proof door and put forward the active decompression concept. The research showed that (1) the shock wave overpressure at the explosion-proof door decreased in a power exponential relationship as the lifting height increased. When the lifting height increased from 0 cm to 5 cm, the peak overpressure at the explosion-proof door decreased from 36.06 kPa to 22.47 kPa, dropping by 37.7%. When it was lifted at a height of 40 cm, the overpressure dropped to 11.20 kPa and the decompression reached 68.9%. (2) The overpressure at the ventilator decreased in a power exponential relationship as the lifting height increased. When the lifting height of the explosion-proof door increased from 0 cm to 5 cm, the decompression ratio reached the maximum 18.4%. After that, the decompression effect became worse and worse. (3) The explosion-proof door could depressurize and protect the ventilator at gas explosion but with limited effects. To protect the ventilator and the explosion-proof door to the maximum, it was suggested that the pressure sensor was set up somewhere in the mine where the gas explosion is likely to occur. In this way, the explosion was sensed in time and the explosion-proof door could be actively lifted for decompression. This paper was of great guiding significance in optimizing the design of the explosion-proof door equipment, reducing the loss of gas explosion accidents as well as carrying out the emergency rescue.

Risk Analysis and Optimization of Water Surface Deviation from Shafts in the Filling–Emptying System of a Mega-Scale Hydro-Floating Ship Lift

Hydro-floating ship lifts are a milestone in the field of high dam navigation. In order to ensure the running safety of a hydro-floating ship lift, the effective integration of a numerical simulation method and cloud model theory was carried out to deal with the hydrodynamic risks presented by water surface deviations from the shafts in the filling–emptying system such as a lock. In this study, the average values of water surface deviation from the shafts were 0.2, 0.22 and 0.24 m, through numerical simulation on a similar hydro-floating ship lift at the lifting heights of 80, 100 and 120 m, respectively. An increase in the lifting height causes the water surface deviation from the shafts to increase, and the hydrodynamic risk is greatly increased in the equal inertial pipeline filling–emptying system. In addition, the water surface deviations from the shafts of the equal inertial pipeline and longitudinal culvert filling–emptying system like a lock were compared. The longitudinal culvert was better at optimizing running safety in the filling–emptying system and dealing with the uncertainty of water surface deviation from the shafts. The results show that the numerical simulation method and cloud model theory can effectively control the risk of water surface deviation from the shafts and can be used to aid in decision-making for risk prevention in relation to hydro-floating ship lifts.

A Study on Factors Affecting the Manual Material Handling Capacity of Indian Male Construction Workers

Construction is one of the most hazardous industries involving high manual labour where health and safety risks are plentiful. This study focuses on evaluating the factors affecting the material lifting capacity of Indian male construction workers. A statistical experiment was conducted on selected male construction workers, and ANOVA technique was used to analyse the influence of parameters (like age, body mass index (BMI), material lifting height and lifting frequency) on maximum allowable weight limit (MAWL). From the analysis, maximum allowable weight limit (MAWL) and minimum lifting weight were determined for every worker based on his age and BMI corresponding to three different lift frequencies and lifting heights. The results indicate that for all BMI categories, the MAWL increases with the increase in the age of workers to a certain extent, but it decreases as the age increases. Using the maximum and minimum lifting weight values obtained, it will be easy to assign manual lifting tasks for workers without compromising their health at the same time ensuring optimum utilization of their efficiency.

Testing to Identify Submaximal Effort: Lifting to a Perceived 50% Effort vs. an Assigned Submaximal Load.

Swift, MC, Townsend, R, Edwards, D, and Loudon, J. Testing to identify submaximal effort: Lifting to a perceived 50% effort vs. an assigned submaximal load. J Strength Cond Res 36(8): 2115-2120, 2022-The ability to accurately measure effort during postinjury functional testing allows for the validation of displayed physical limitations by injured workers. The Cross-Reference Testing System (XRTS) has been developed to identify submaximal efforts through distraction-based dynamic material handling testing. The XRTS material handling assessment compares dynamic lifts of weights in a crate and lifts using a lever arm device. The purpose of this study was to determine whether subjects lifting an assigned submaximal load influence test results compared with subjects lifting to but not exceeding a 50% perceived effort. Subjects in group A ( n = 35) were assigned the condition to attempt to lift to but not exceed a randomly assigned weight value for both the crate lift and XRTS at 3 lifting heights. Subjects in group B ( n = 32) were asked to lift to but not exceed 37.5 lb from the same 3 lifting heights. The reproducibility of effort was measured with current validity criteria for distraction-based material handling testing. Using the percent difference values, a 2 × 3 (group, lifting height) analysis of variance (ANOVA) was performed to test the hypothesis. The alpha level was set at 0.05. The mean percent change between comparative lifts was 31.13%, 95% CI (22.51-39.75) for group A and 29.26% 95% CI (21.91-36.61) for group B. The 2 × 3 ANOVA demonstrated no significant difference ( p = 0.751) between groups. The results indicate attempting to lift to a perceived 50% effort was not significantly different from attempting to lift to but not exceed an assigned submaximal load.

Energochłonność i poprawa efektywności energetycznej mechanizmów suwnicy pomostowej

The article presents the numerical investigation of the overhead crane’s energy consumption. The analysis is based on the hybrid model of the crane consisting of numerical model of drive mechanisms as bridge, trolley, hoist and also experimentally measured power consumption of each control unit. The numerical model was verified experimentally on the real crane. The investigation focuses on analyzing the energy consumption of the overhead crane in relation both to the travelled distance and also for the lifting and lowering heights of a suspended payload. Particular attention was paid on the cases straightly related to the hoist, as a main factor of improvements in the energetic efficiency of the overhead crane. Energy consumption was investigated for a variety of magnitudes of transported mass

Determining Changes in Electromyography Indices when Measuring Maximum Acceptable Weight of Lift in Iranian Male Students

In spite of the increasing degree of automation in industry, manual material handling (MMH) is still performed in many occupational settings. The aim of the current study was to determine the maximum acceptable weight of lift using psychophysical and electromyography indices. This experimental study was conducted among 15 male students recruited from Tehran University of Medical Sciences. Each participant performed 18 different lifting tasks which involved three lifting frequencies, three lifting heights and two box sizes. Each set of experiments was conducted during the 20 min work period using free-style lifting technique and subjective as well as objective assessment methodologies. SPSS version 18 software was used for descriptive and analytical analyses by Friedman, Wilcoxon and Spearman correlation techniques. The results demonstrated that muscle activity increased with increasing frequency, height of lift and box size (P<0.05). Meanwhile, MAWLs obtained in this study are lower than those in Snook table (P<0.05). In this study, the level of muscle activity in percent MVC in relation to the erector spine muscles in L3 and T9 regions as well as left and right abdominal external oblique muscles were at 38.89%, 27.78%, 11.11% and 5.55% in terms of muscle activity is more than 70% MVC, respectively. The results of Wilcoxon test revealed that for both small and large boxes under all conditions, significant differences were detected between the beginning and end of the test values for MPF of erector spine in L3 and T9 regions, and left and right abdominal external oblique muscles (P<0.05). The results of Spearman correlation test showed that there was a significant relation between the MAWL, RMS and MPF of the muscles in all test conditions (P<0.05). Based on the results of this study, it was concluded if muscle activity is more than 70% of MVC, the values of Snook tables should be revisited. Furthermore, the biomechanical perspective should receive special attention in determining the standards for MMH.

Elevated Mixed Layers and Associated Severe Thunderstorm Environments in South and North America

Abstract This study presents a climatological and composite analysis of elevated mixed layers (EMLs) in South and North America derived from the NCEP Climate Forecast System Reanalysis. The EMLs are identified based on objective criteria applied to the reanalysis data. Composite analyses of synoptic-scale conditions and severe weather parameters associated with spring EML cases are presented. EMLs are more frequent immediately to the east of the Andes and the Rockies. The North American EMLs form by surface heating over the higher terrain of the Rockies, with peak frequency occurring in spring and summer. EMLs in South America are generated by differential temperature advection due to ageostrophic circulations east of the Andes, as indicated by the temperature lapse rate tendency equation, which relates to the higher frequency of EMLs during the cold season in South America. EMLs over North America are about 100 hPa lower than over South America due to the lower height of the Rockies in comparison to the Andes. The synoptic conditions associated with EMLs in South and North America are characterized by an upper-level trough upstream and low-level moisture flux convergence due to poleward-directed flow, favoring synoptic-scale ascent poleward of the EML location, where the convective inhibition is relatively low. When EMLs occur, higher surface-based convective available potential energy and low-level storm-relative helicity, in association with lower lifting condensation level heights observed in North America, indicate that surface-based supercell storms and tornadoes are more likely to occur on this continent in comparison with South America, corroborating observations.

Factors determining workers' pace while conducting continuous sequential lifting, carrying, and lowering tasks

To plan a new manual material handling work process, it is necessary to predict the times required to complete each task. Current time prediction models lack validity when the handled object's mass exceeds 2 kg. In this study, we investigated the effect of workplace design parameters on continuous sequential lifting, carrying, and lowering of boxes weighing from 2 kg to 14 kg. Both laboratory and field experiments were conducted. Results revealed that the box's weight and the lifting and lowering heights influenced the tasks' times. Further, the time to perform a task was influenced by the performance of other tasks in the same work process. New time prediction models were developed using the laboratory experiment data. Our models were found to be more accurate on average than the Maynard Operation Sequence Technique (MOST) and Methods Time Measurement (MTM-1) by 42% and 20%, respectively, for predicting the times of real workers at an actual workplace.

The Statistical Severe Convective Risk Assessment Model

Abstract This study introduces a system that objectively assesses severe thunderstorm nowcast probabilities based on hourly mesoscale data across the contiguous United States during the period from 2006 to 2014. Previous studies have evaluated the diagnostic utility of parameters in characterizing severe thunderstorm environments. In contrast, the present study merges cloud-to-ground lightning flash data with both severe thunderstorm report and Storm Prediction Center Mesoscale Analysis system data to create lightning-conditioned prognostic probabilities for numerous parameters, thus incorporating null-severe cases. The resulting dataset and corresponding probabilities are called the Statistical Severe Convective Risk Assessment Model (SSCRAM), which incorporates a sample size of over 3.8 million 40-km grid boxes. A subset of five parameters of SSCRAM is investigated in the present study. This system shows that severe storm probabilities do not vary strongly across the range of values for buoyancy parameters compared to vertical shear parameters. The significant tornado parameter [where “significant” refers to tornadoes producing (Fujita scale) F2/(enhanced Fujita scale) EF2 damage] exhibits considerable skill at identifying downstream tornado events, with higher conditional probabilities of occurrence at larger values, similar to effective storm-relative helicity, both findings being consistent with previous studies. Meanwhile, lifting condensation level heights are associated with conditional probabilities that vary little within an optimal range of values for tornado occurrence, yielding less skill in quantifying tornado potential using this parameter compared to effective storm-relative helicity. The systematic assessment of probabilities using convective environmental information could have applications in present-day operational forecasting duties and the upcoming warn-on-forecast initiatives.

Effect of coal-limestone mixtures on dust dispersion behind a moving shock wave

Secondary dust explosions in coal mines or industrial settings are known to cause greater catastrophic hazards than the coupled primary explosions themselves. The shock waves produced during a primary explosion lift surrounding coal particles from neighboring areas, and if added in an effort to create an inert mixture, limestone as well. This experimental study characterized the coupled effects of dust dispersion from coal-limestone mixtures and moisture-varied limestone dust. A shock tube modified to evaluate dust dispersion provided the optical access to characterize the shock wave/dust-layer interaction. The moisture-varied limestone samples were tested at three shock Mach numbers, namely Ms = 1.1, 1.23, and 1.4, with trending data showing an average increase of 10% in overall lifting heights and 20% in initial linear growth rates for the moisture-reduced, dried samples, as compared to undried samples stored in standard temperature and pressure (STP) conditions. The coal-limestone mixture samples were tested at two shock Mach numbers, namely Ms = 1.24 and 1.57, with the 75% limestone sample having the highest and the 25% limestone sample having the lowest effective dust dispersion effects. Conceivably, the effective moisture reduction in the samples led to fewer agglomerations and/or reduced densities, influencing the ability of lift forces to act on the particles, while as the limestone content was increased in coal-limestone mixtures, dust layers grew faster, larger, and transitioned into more pronounced instabilities on the dust-gas boundaries. The combined effects of dispersion, SEM imagery, and the study of test facility shadowgraphs lead to recommending the ignition-inhibiting coal-limestone mixture containing 50% limestone. The dust-layer rise height was measured with respect to time after the shock passage, where regardless of mixture-ratio or moisture content in the samples, initial linear dust growth rates increased with shock Mach number. Linear and unstable regimes were also identified in the data samples, as seen in previous studies by the authors.

Effects of box size, frequency of lifting, and height of lift on maximum acceptable weight of lift and heart rate for male university students in Iran.

IntroductionIn spite of the widespread use of automation in industry, manual material handling (MMH) is still performed in many occupational settings. The emphasis on ergonomics in MMH tasks is due to the potential risks of workplace accidents and injuries. This study aimed to assess the effect of box size, frequency of lift, and height of lift on maximum acceptable weight of lift (MAWL) on the heart rates of male university students in Iran.MethodsThis experimental study was conducted in 2015 with 15 male students recruited from Tehran University of Medical Sciences. Each participant performed 18 different lifting tasks that involved three lifting frequencies (1lift/min, 4.3 lifts/min and 6.67 lifts/min), three lifting heights (floor to knuckle, knuckle to shoulder, and shoulder to arm reach), and two box sizes. Each set of experiments was conducted during the 20 min work period using the free-style lifting technique. The working heart rates (WHR) were recorded for the entire duration. In this study, we used SPSS version 18 software and descriptive statistical methods, analysis of variance (ANOVA), and the t-test for data analysis.ResultsThe results of the ANOVA showed that there was a significant difference between the mean of MAWL in terms of frequencies of lifts (p = 0.02). Tukey’s post hoc test indicated that there was a significant difference between the frequencies of 1 lift/minute and 6.67 lifts/minute (p = 0. 01). There was a significant difference between the mean heart rates in terms of frequencies of lifts (p = 0.006), and Tukey’s post hoc test indicated a significant difference between the frequencies of 1 lift/minute and 6.67 lifts/minute (p = 0.004). But, there was no significant difference between the mean of MAWL and the mean heart rate in terms of lifting heights (p > 0.05). The results of the t-test showed that there was a significant difference between the mean of MAWL and the mean heart rate in terms of the sizes of the two boxes (p = 0.000).ConclusionBased on the results of this study, it was concluded that MAWL and heart rate are influenced by the variables of lifting frequency and the size of the boxes.

Effects of different lifting and lowering heights on upper arm, shoulder and back muscle activity during a manual material handling task.

Previous research has suggested eliminating certain types of manual material handling (MMH) work by recommending specific arm angles and postures to avoid, such as arm flexion or abduction over 90°. MMH with arm flexion over 90° can require lifting objects as well as lowering objects. However, few studies have evaluated MMH work while lowering objects in detail. This study investigated the effects of different lifting and lowering heights on upper arm, shoulder, and back muscle activity during a MMH task. The participants performed a MMH task that involved stoop lowering and lifting. The participants transferred the box to shelves positioned 30 cm in front of them under various conditions. Conditions 1 to 4 involved transferring the box to 1) ankle-, 2) knee-, 3) waist-, and 4) shoulder-high shelves, respectively. Surface electrodes were attached to the biceps brachii, upper trapezius, rhomboid minor, and L4 erector spinae. The activity of the biceps brachii was decreased significantly in Conditions 1 and 2 compared to Conditions 3 and 4. The upper trapezius activity was increased significantly in Conditions 1 and 4 compared to Conditions 2 and 3. The rhomboid minor activity increased significantly in Condition 1 compared to Conditions 2 to 4. The L4 erector spinae activity decreased significantly in Condition 1 compared to Conditions 2 to 4 CONCLUSIONS:A low-lowering MMH work could contribute to neck, shoulder, and back pain. Therefore, further studies must examine a height below-knee MMH work in detail.

Psychophysical Experience and Heart Rate Analysis in Manual Lifting Task of Malaysian Population

Back pain is one of the prevalent injuries that occurs among Malaysian industrial workers. This is due to manual lifting task. Minimal studies have been conducted to determine the effects of manual lifting on psychophysical experience and heart rate of Malaysian population. The objective of this study is to analyze the psychophysical experience and heart rate of Malaysian in manual lifting task. The lifting task was experimented at various lifting heights (55 cm, 75 cm and 140 cm); loads with masses of 5 kg, 10 kg and 13 kg; and twist angles (0°, 45° and 90°). Six male and six female Malaysian students participated as subjects in the experiment. The Likert Scale was used to evaluate the psychophysical experience; meanwhile the heart rate monitor (Polar FT2, Finland) was applied to measure the heart rate. This study discovered that the psychophysical experience recorded the highest rating when performing lifting test at maximum load mass (13 kg), lifting height of 130 cm, and twist angle of 90°. Furthermore, the subjects experienced the highest heart rate after performing lifting test at maximum lifting height (130 cm) and load mass of 13 kg. This study concluded that the load mass, lifting height, and twist angle are proportional to the level of psychophysical experience. Additionally, when the load mass and lifting height were increased, the heart rate was also increased.

Block Mechanism of Microclearance Block Liquid and Lifting Height Calculating

Mechanical seal mechanism was applied to study block mechanism of gaswell microclearance block liquid for the first time, which explained block mechanism of microclearance block liquid. The paper has built a block physical model of microclearance block liquid and has got calculation formulas of the block liquid lifting height. Then the block liquid lifting heights were calculated and analyzed in different microclearance widths and pressures. The sealing effect of the block liquid was discussed. The analyzed results showed that sealing effect of the block liquid was very obvious when microclearance width was lesser than 12μm. The paper not only enriched the study on block mechanism of gaswell microclearance block liquid but also proposed theoretical guidance to solve radically gas migration problem of micro-annulus.