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Settling model to predict microplastics removal efficiency in wastewater treatments

AbstractMicroplastics (MPs) are plastic particles less than 5 mm and become a good carrier and vectors for contaminants in the environment. Current wastewater treatment technologies, including preliminary treatment, primary treatment, secondary treatment, and tertiary treatment, have a certain removal efficiency for MPs or nano‐scale plastic particles. The settling treatment is employed in several wastewater treatment processes. This work built a settling model based on the Reynolds number, drag coefficient, and settling mechanism to predict the microplastics removal efficiency. Microplastics with larger density difference with wastewater, larger size, and CSF closer to 1 are easily captured and have a higher removal efficiency. The calculated removal efficiency according to density, size distribution, different shapes, and the surface loading rate in the operation of wastewater treatment is in a reasonable removal efficiency range. The removal efficiency increases when the surface loading rate decreases.

Quasistatic nature of subsurface densification of soda lime silicate glass under nano- and Vickers indentation

Mechanical properties of glass are critical for technical applications, thus comprehending the material response to mechanical tests is of great importance. In this study, we employ the nanoindentation combined with nanoscale infrared (nano-IR) spectroscopy combined with scattering-type scanning near-field optical microscopy (s-SNOM) and ToF-SIMS, to elucidate the nanoindentation rate dependence of plastic deformation of soda lime silicate glass. Experiment results show that the nanohardness and elastic modulus of soda lime silicate (SLS) glass exhibit a strong dependence on loading rate, while those of fused quartz (FQ) shows a much weaker dependence. The residual indent volume at fast loading conditions is smaller for SLS glass than FQ; but as the loading rate decreases, the residual indent volume of FQ and SLS glass becomes similar. The indent volume of SLS glass after sub-Tg annealing (reverting subsurface densification) shows negligible dependence on the loading rate, suggesting that the densification of SLS glass is strongly enhanced at lower indentation rate, but the shear flow is independent or weakly dependent. Using nanoscale infrared spectroscopy and ToF-SIMS techniques, the sodium ion migration in SLS glass surface in the indent is found to be associated with the subsurface densification. These results suggest the possible role of highly mobile sodium ions on in nano- and micro-scale plastic deformation behavior of SLS glass.

An analytical approach to deduce loading rate-sensitivity of fracture mode of concrete and mortar

The fracture of two-component solids is considered in order to study the sensitivity of the failure mode to the loading rate. The incubation time approach, supplemented by the randomized Sign-Perturbed Sums (SPS) method, is applied to develop an analytical model to predict the difference in the fracture pattern under dynamic and static conditions. To verify and validate the model, experimental data of dynamic tests on concrete, mortar and granite aggregate are analyzed. It was demonstrated that the model indicates the change in the failure mode for inhomogeneous material such as concrete, while the analysis results for pure granite do not predict the same phenomenon. The results obtained are in agreement with the experimentally observed change in the fracture mechanism of concrete from transgranular to intergranular as the loading rate decreases. Thus, it was shown that the developed model is able to predict the change of the fracture mechanism with the increase of the loading rate.

Improving conductivity and self-sensing properties of magnetically aligned electroless nickel coated glass fiber cement

The nickel coated glass fiber (Ni-GF) cement (NGFC) holds promise for self-sensing concrete structure due to its improved conductivity and corrosion resistance. This paper is aimed at evaluating the conductivity and self-sensing properties of preferentially orientated NGFC, which was prepared by the magnetic field (MF) induction. The microstructure of electroless Ni-GFs and their arrangement characteristic in cement were observed by optical microscope (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The anisotropic conductivity and self-sensing properties of as-prepared composites were measured by four-electrode method. The results indicate that the Ni-GFs with uniform nickel coating layer in the as-fabricated composite have an excellent alignment effect under the MF induction. When the Ni-GF content is 2.62 vol%, the composite exhibits maximum anisotropy. The order of the electrical resistivity and percolation thresholds of NGFC is: parallel to MF < without MF < perpendicular to MF. Under the cyclic compression load, the NGFC parallel to MF shows the optimum self-sensing properties. With the increase of loading amplitude and decrease of loading rate, the maximum sensitivities of the as-prepared composite at all directions almost increase linearly. Under the failure compression load, the conductivity of as-prepared composites parallel to MF show a steadier and higher self-sensing response.

Deformation-softening behaviors of high-strength and high-toughness steels used for rock bolts

In deep ground engineering, the use of high-strength and high-toughness steels for rock bolt can significantly improve its energy absorption capacity. However, the mechanisms and effects of rock loading conditions on this kind of high energy-absorbing steel for rock bolt remain immature. In this study, taking Muzhailing highway tunnel as the background, physically based crystal plasticity simulations were performed to understand the effect of rock loading rate and pretension on the deformation behaviors of twinning induced plasticity (TWIP) steel used for rock bolt. The material physical connecting to the underlying microscopic mechanisms of dislocation glide and deformation twinning were incorporated in numerical modeling. The rock loading conditions were mimicked by the real-time field monitoring data of the NPR bolt/cable equipment installed on the tunnel surrounding rock surface. The results indicate that the bolt rod exhibits pronounced deformation-softening behavior with decrease of the loading rate. There is also a sound deformation-relaxation phenomenon induced by the dramatic decrease of loading rate after pre-tensioning. The high pretension (>600 MPa or 224 kN) can help bolt rod steel resist deformation-softening behavior, especially at low loading rate (<10−1 MPa/s or 10−2 kN/s). The loading rate was found to be a significant factor affecting deformation-softening behavior while the pretension was found to be the major parameter accounting for the deformation-relaxation scenario. The results provide the theoretical basis and technical support for practical applications.

Моделювання явища крихкопластичного переходу методом дислокаційної динаміки

Computer modeling by the DD method is based on the Rice and Thompson model, according to which the force reliefnear the crack tip is created by three forces: an external load, an image force acting on dislocations from the free surfaces, and a resistance force from the crystal lattice. The interaction between dislocations in the plastic zone is calculated step by step. At each step, the stress is calculated for all dislocations in the ensemble and the velocities and corresponding new positions are calculated. Computer calculations make it possible to predict the impact of dislocation ensemble shielding on the current value of the stress intensity factor. The calculated value of crack resistance was determined under the condition of reaching the critical value of the stress intensity coefficient of the brittle material at the crack head. The effect of temperature and strain rate on the viscous-brittle transition in polycrystalline molybdenum was modeled using the dislocation dynamics method. From the results of the calculations, it follows that when the test temperature changes, the size of the plastic zone increases by more than an order of magnitude. As the loading rate decreases, the abnormal increase in crack resistance shifts to smaller grain sizes. This effect is significantly smaller than the effect of temperature. Changing the parameters of the model does not change the general mechanism of the viscous-brittle transition, which is associated with the peculiarities of the interaction of dislocations in the plastic zone with grain boundaries in polycrystalline molybdenum. Regardless of the speed of loading and the temperature of the tests, three characteristic ranges of grain sizes can be distinguished: With large grains, the fracture toughness remains unchanged because the size of the plastic zone is much smaller than the grain size. With the average grain size, a dislocation cluster is formed near the boundary, grain boundary sources begin to work in the neighboring grain, forming a small number of dislocations there, which contributes to a slight increase in crack resistance. With a small grain size, the fracture toughness begins to increase rapidly, since the plastic zone covers several grains. The dislocation cluster moves to the top of the crack and screens its propagation. Keywords: phenomenon of brittle-plastic transition, dislocation clustering, dislocation dynamics.

Long-term phosphorus sorption and leaching in sand filters for onsite treatment systems

The sorption capacities of sand filters used for onsite wastewater treatment and their associated risks of phosphorus (P) leaching on contact with rainwater were investigated in column experiments and with modelling tool for over 300 days. Columns packed with sand were exposed to real domestic wastewater of different characteristics and hydraulic loading modes. The wastewater fed into the columns was effluent collected from three different treatment units in the field: a septic tank (ST), biofiltration tank (BF) and Polonite® filter bag (PO). The risk of P leaching to groundwater and surface water was also assessed, by exposing the same sand columns to natural rainwater. Overall results indicated that sand soils can exhibit different adsorption and desorption capacities for electrical conductivity (EC), Total-P, phosphate-P and total suspended solids, depending on the characteristics of influent wastewater, loading rate and total operation time. The removal efficiencies of the sand columns increased in the order ST (98.16%) > PO (93.36%) > BF (81.57%) for PO4-P and slightly decreased ST (97.11%) > PO (92.06%) > BF (76.76%) for Total-P columns. All sand columns loaded with actual wastewater solutions from septic tanks and biofiltration tank have demonstrated high risks of phosphorus leaching (>99.99%) to the groundwater. The modelling was successful captured behavior of EC tracer and adsorption of PO4-P with acceptable prediction uncertainty in the PO < 8% columns. The modelling results indicated that the decrease of loading rate from 83.3 mL d-1 to 20.83 mL d-1 led to an average increase of removal efficiency and prolong operational lifetime and mass of adsorbed Total-P in the sand soil. This study concludes that sand is a valuable filter medium at low loading rate for phosphorus removal in full-scale operations of onsite treatment systems, however very vulnerable for leaching P when in contact with rainwater.

Experimental Study on the Characteristics of Acoustic Emission Source of Rock under Uniaxial Compression

One of the main research problems in acoustic emission (AE) monitoring technology is to identify the source of the acoustic emission. Processing the acoustic emission signal is the only way to solve this problem, and then to achieve the purpose of identifying the material destruction mode. Using acoustic emission monitoring technology, the acoustic emission of granite under uniaxial compression was monitored and analyzed, and the coupling characteristics between the acoustic emission signal parameters of granite under different loading rates were obtained. The results show that during the process of rock shear failure, the peak intensity of the rock, the peak value of the absolute energy of acoustic emission, the cumulative amount of acoustic emission and the loading rate showed a positive correlation. The correlation diagram of the AE ringing count and the duration shows a triangular distribution, and as the rock loading rate decreases, the angle of the triangle top angle of the correlation diagram increases. The distribution relationship between the absolute energy of AE and the duration can be fitted using a unary quadratic function, and as the loading rate decreases, the opening of the fitting curve gradually increases, and the width of the correlation graph gradually decreases. The correlation graph of absolute energy and amplitude of AE is linearly distributed, and as the loading rate decreases, the slope of the fitted line of absolute energy and amplitude of AE gradually decreases, and the width of the linear channel of the correlation graph decreases. It is found that there is a good regularity between the correlation graphs of different parameters of the acoustic emission of the rock during the uniaxial compression failure process, which is an effective method to identify the characteristics of the source of the acoustic emission. Therefore, establishing the correspondence between the characteristics of the AE source and the loading conditions will promote the development of acoustic emission technology in the monitoring of the stability of the surrounding rock of underground projects.

Numerical simulation on coal loading process of shearer drum based on discrete element method

The drum is the working mechanism of the coal shearer, and the coal loading performance of the drum is very important for the efficient and safe production of coal mine. In order to study the coal loading performance of the shearer drum, a discrete element model of coupling the drum and coal wall was established by combining the results of the coal property determination and the discrete element method. The movement of coal particles and the mass distribution in different areas were obtained, and the coal particle velocity and coal loading rate were analyzed under the conditions of different helix angles, rotation speeds, traction speeds and cutting depths. The results show that with the increase of helix angle, the coal loading first increases and then decreases; with the increase of cutting depth and traction speed, the coal loading rate decreases; the increase of rotation speed can improve the coal loading performance of drum to a certain extent. The research results show that the discrete element numerical simulation can accurately reflect the coal loading process of the shearer drum, which provides a more convenient, fast and low-cost method for the structural design of shearer drum and the improvement of coal loading performance.

Change in Force-based Metrics during Outdoor 2- and 4-Mile Runs.

The purpose of this study was to determine if peak ground reaction force (GRF), loading rate (LR), and impulse metrics change across an outdoor run using force sensing insoles. We hypothesize that over the course of the run there would be a decline in limb symmetry for all measures and a decrease in LR and GRF values. Thirty healthy participants (15 male, 15 female) were recruited for a two-visit study during which a 2- or 4-mile run was completed on the first visit and the other run distance was completed on the second visit (order was randomized). Force data were collected at 100 Hz for the duration of the run. Peak GRF, impulse, LR, and limb symmetry indices (LSI) of these variables were calculated at 25%, 50%, and 75% of the run. GRF decreased over the course of the runs, but the GRF LSI remained unchanged. No changes in LR were detected over the 2- or 4-mile run for either limb. The impulse LSI during the 2-mile run did indicate decreased symmetry from 25% of the run to 50% of the run, the LR LSI improved, and there was no difference in GRF LSI or any of the LSI metrics during the 4-mile run. We posit that the lack in change in LSI was due to the courses/distance not inducing fatigue in our population. Future studies should investigate the effect of outdoor fatigue protocols and various types of terrain on force metrics and potential injury risk factors.

Application and Effect of Loading Rates on Coal Sample Failure

In order to evaluate the coal pillar stability in recovery of residual room pillars under different mining rates, this paper studies the influence of loading rate on the mechanical properties of the coal body. The uniaxial compression tests of coal samples in Yangcheng area at different loading rates were carried out with the MTS815 electrohydraulic servo rock mechanics test system. The stress‐strain curves and the evolution characteristics of AE signals were analyzed. At same time, the mechanism of damage and failure of specimens are also discussed. The results show the following. (1) With the increase in loading rate, the ultimate stress and ultimate strain of specimens decrease first and then increase. (2) Loading rate has a significant effect on the stability adjustment of specimens. With the decrease in loading rate, the earlier the stress adjustment is, the larger the adjustment range is, and the failure mode changes from shear failure to tensile failure. (3) In addition, when the loading rate increases, the AE evolves from continuous dense to discrete catastrophe, which indicates that the failure of the sample at a larger loading rate is sudden, which is not conducive to the maintenance of the stability of the coal pillar. (4) Finally, the failure mechanism of the specimen structure under different loading rates is obtained, and the improvement measures for the effect of mining velocity of working face on the stability of coal pillar are put forward. The results reveal the loading rate effect of mechanical properties of coal and provide a reference for controlling the stability of the residual coal pillar.

Reach and geometry of dynamic gas-driven fractures

Dynamic gas fracturing is a well stimulation technique that is able to create multiple fractures emanating from a wellbore. It operates by pressurizing at rise-times and peak pressures intermediate between conventional hydraulic fracturing and explosive fracturing. Two consecutive processes operate during this fracturing process: (i) generation and propagation of a dynamic stress wave that overpowers the static stress field and creates multiple radial fractures around borehole, followed by (ii) quasi-static pressurization and further extension of those starter-fractures by the expanding gas. Dynamic analysis is first performed to follow the evolution of the stress wave propagating from the borehole. The radial (r) distribution of peak tensile hoop-stress diminishes as 1/rα with the power exponent (α) asymptoting to 2 as the loading rate decreases. This rapid attenuation generally limits the length of the body-wave-generated radial fractures to several borehole radii. The gas-loading of the borehole wall is followed by permeation of the gas pressure into the newly created radial fractures. Linear elastic fracture mechanics (LEFM) perturbation analysis shows that a regular distribution of multiple radial starter-cracks will preferentially propagate the longer cracks at the expense of the shorter cracks – that will arrest and snap-shut. This system naturally selects of the order of six dominant fractures that may grow in unison until the in situ stress field reasserts control as the fractures lengthen. This restricts the maximum number of the dominant fractures to of the order of six at the conclusion of treatment - a common observation in both in situ and laboratory experiments.

UNDRAINED CYCLIC SHEAR BEHAVIOR OF CLAY UNDER DRASTICALLY CHANGED LOADING RATE

The earthquake damage prediction is mainly focused on the seismic instability of sandy foundations although the clayey foundation could also be vulnerable to earthquake damage. Moreover, it is known that clayey soil shows a marked loading rate dependency in monotonic shear behavior due to its low permeability. Therefore, this paper aims to determine the undrained cyclic shear behavior of clayey soilunder a drastically changed loading rate. Reconstituted clayey samples were subjected to undrained cyclic triaxial compression/extension tests with loading rate from 1.0Hz to 0.0042Hz by stress control, and 0.01%/min by strain control. The cyclic loading was stopped when the double amplitude exceeded 5%. Then, the specimen was left for a while in an undrained condition, until the value of pore water pressure converged.Results revealed that as the loading rate decreases, the number of cycles that corresponds to DA=2% and 5% also decreased. Therefore, the degree of strain evolution varies depending on the loading rate and the undrained shear strength also varies depending on the cyclic loading rate. This is because when the cyclic loading rate was high; the pore water did not migrate sufficiently, leading to the non-uniform distribution of the excess pore water pressure inside the specimen. However, the final values of excess pore water pressure after the homogenization process was the same regardless of the loading rate. This means that if sufficient time is left after cyclic loading, the final mean effective stress value becomes equal regardless of the loading rate

Power generation performance of dielectric elastomer generator with laterally-constrained configuration

A new loading method with laterally-constrained configuration was proposed to study the energy conversion behavior of dielectric elastomer generator (DEG) based on experimental tests and theoretical calculation. The influence of lateral pre-stretch ratio and the loading rate on the energy transformation of DEG (VHB 4905) was investigated under both the quadrangular and triangular harvesting schemes, and the latter shows higher energy density and conversion efficiency than the former. The energy density increases with the lateral pre-stretch ratio at the range of 2 to 4, with the maximum value of 76 mJ g−1 for the quadrangular cycle and 186 mJ g−1 for the triangular cycle at the loading rate of 90 mm s−1 (strain rate of 2 s−1), respectively. The advantage of larger lateral pre-stretch ratio is mainly attributed to the increased capacitance density of the elastomer membrane at the maximum stretch, which enlarges the operational area confined by multiple failure limits on the voltage-charge work-conjugate plane. As the loading rate decreases, the energy density within each cycle decreases monotonically due to the increased charges leakage. Since the mechanical energy loss within a single cycle decreases at the lower loading rate, the conversion efficiency for the triangular cycle shows slight increase at the lower loading rate, with the maximum value of 15.4% for stretching rate of 50 mm s−1 (strain rate of 1.11 s−1).

Fracture properties of asphalt concrete under various displacement conditions and temperatures

Fracture mechanics has been widely applied to asphalt concrete (AC) materials to evaluate the cracking potential of AC pavements under traffic and thermal loadings. While AC materials behave as quasi-brittle at low temperature and high loading rate, its behavior becomes more viscous as temperature increases and/or loading rate decreases. Considerable fracture tests have been developed to capture the fracture properties of AC materials; however, fracture properties may be misinterpreted when using various fracture tests, especially in bending-mode. This would result in an erroneous characterization of AC cracking potential, which leads to a misestimate of pavement service life. The objective of this study is to investigate common fracture test methods for the AC materials, compare the fracture energies from various displacement measurements to capture true fracture property, and examine the effect of temperature on fracture energy and Flexibility Index (FI). Fracture energy from the semi-circular bending (SCB) geometry was compared to that from the disk-shaped compact tension (DCT) test. The effect of misinterpretation of test results on fracture energies was investigated. This study also suggests a proper method to capture fracture properties from the SCB test using the basic understanding of work and energy concepts in physics. The effects of test temperature on (1) fracture energy values, (2) FI, and (3) the overall ability to discriminate the cracking potential of AC mixtures are presented. Results show that while the crack characteristics can be captured more reasonably with a Load-Crack Mouth Opening Displacement (CMOD) curve, the fracture energy is better obtained using load-Load Line Displacement (LLD) curve. Moreover, performing fracture tests at a relatively higher temperature increases the ability to distinguish between various AC mixtures’ cracking potential.

Determination of fatigue life of the unidirectional GFRP/Al hybrid composite laminates

This paper investigates the effects of loading rate and fiber orientation on the fatigue behavior of the unidirectional glass-fiber reinforced-plastic/aluminum (GFRP/Al) hybrid laminated (GLARE-2) plates. Fatigue tests were performed at three kinds of stress ratios (R = 0.3, 0.1, and −0.1) on specimens with different fiber orientations, θ = 0°, 15°, 30°, 45°, 60°, 75°, and 90°, in the GFRP layers. All the fatigue results to be presented in this article were obtained in repeated tension-tension and tension-compression at stress ratios of 0.3, 0.1, and −0.1, and the results were compared with each other. It has been shown that the specimens have the highest fatigue life in the fiber orientation direction at R = 0.3 loading rate. Also, it has been shown that the fatigue life of the specimens decreases as the loading rate decreases.

Inter-isotope effects in optimal dual-isotope loading into a shallow optical trap

Examination of loading the isotopes 85Rb and 87Rb simultaneously into a shallow far-off-resonance trap (FORT) has revealed an unexpected decrease in maximum atom number loaded as compared to loading either isotope alone. The simultaneous loading of the FORT will be affected by additional homonuclear and heteronuclear light-assisted collisional losses. However, these losses are measured and found to be insufficient to explain the observed drop in the total number of atoms loaded into the FORT. We find that our observations are consistent with a decrease in loading rate caused by inter-isotope disruptions of the efficient laser cooling required to load atoms into the optical trap.

Development of a Novel Bioelectrochemical Membrane Reactor for Wastewater Treatment

A novel bioelectrochemical membrane reactor (BEMR), which takes advantage of a membrane bioreactor (MBR) and microbial fuel cells (MFC), is developed for wastewater treatment and energy recovery. In this system, stainless steel mesh with biofilm formed on it serves as both the cathode and the filtration material. Oxygen reduction reactions are effectively catalyzed by the microorganisms attached on the mesh. The effluent turbidity from the BEMR system was low during most of the operation period, and the chemical oxygen demand and NH(4)(+)-N removal efficiencies averaged 92.4% and 95.6%, respectively. With an increase in hydraulic retention time and a decrease in loading rate, the system performance was enhanced. In this BEMR process, a maximum power density of 4.35 W/m(3) and a current density of 18.32 A/m(3) were obtained at a hydraulic retention time of 150 min and external resister of 100 Ω. The Coulombic efficiency was 8.2%. Though the power density and current density of the BEMR system were not very high, compared with other high-output MFC systems, electricity recovery could be further enhanced through optimizing the operation conditions and BEMR configurations. Results clearly indicate that this innovative system holds great promise for efficient treatment of wastewater and energy recovery.

A method to characterize in vivo tendon force–strain relationship by combining ultrasonography, motion capture and loading rates

The ultrasonography contributes to investigate in vivo tendon force–strain relationship during isometric contraction. In previous studies, different methods are available to estimate the tendon strain, using different loading rates and models to fit the tendon force–strain relationship. This study was aimed to propose a standard method to characterize the in vivo tendon force–strain relationship. We investigated the influence on the force–strain relationship for medialis gastrocnemius (MG) of (1) one method which takes into account probe and joint movements to estimate the instantaneous tendon length, (2) models used to fit the force–strain relationship for uniaxial test (polynomial vs. Ogden), and (3) the loading rate on tendon strain. Subjects performed ramp-up contraction during isometric contractions at two different target speeds: 1.5s and minimal time with ultrasound probe fixed over the muscle–tendon junction of the MG muscle. The used method requires three markers on ultrasound probe and a marker on calcaneum to take into account all movements, and was compared to the strain estimated using ultrasound images only. The method using ultrasound image only overestimated the tendon strain from 40% of maximal force. The polynomial model showed similar fitting results than the Ogden model (R²=0.98). A loading rate effect was found on tendon strain, showing a higher strain when loading rate decreases. The characterization of tendon force–strain relationship needs to be standardized by taking into account all movements to estimate tendon strain and controlling the loading rate. The polynomial model appears to be appropriate to represent the tendon force–strain relationship.

Elevated Temperature Properties of Pinned Composite Lap Joints

Reinforcement in the through-thickness direction with pins improves the elevated temperature strength and damage tolerance of polymer composite joints. The failure modes and ultimate strength are experimentally determined for carbon/epoxy single-lap joints at temperatures between 20 and 250°C. Pinning improves the ultimate strength, elongation-to-failure limit, and work of fracture of the joints over the entire temperature range, by factors that depend on the orientation, volume content and diameter of the pins. The dominant strengthening mechanism at elevated temperature is crack bridging by the pins, which increases the ultimate joint strength by as much as 60%. However, rate-dependent mechanisms increasingly negate the benefit of pins as the temperature rises above approximately 125°C. This threshold temperature is 40°C less than the glass transition temperature for the laminate resin. For tests conducted at a constant rate of increase of load, rate dependence appears as a reduction of the failure load with increasing test temperature. A simple model derived by introducing rate-dependent sliding between the pins and the laminate into a previous model of the mechanics of pin bridging fits the data for strength reduction well, if the sliding rate is assumed to increase exponentially with temperature. The model predicts that the ultimate strength will decrease as the loading rate decreases, for loading that increases linearly with time. The fractional reduction of strength for a given temperature is approximately independent of the pin half-length and area fraction; and greater reduction should occur for larger pin diameter if the pin half-length and volume content are fixed.