Hard Packing Research Articles

Research and Development of the Treatment Effectiveness of a Novel Process for Vegetable Biogas Slurry Purification

Nowadays, an anaerobic filter is used in treating various wastewaters that is more effective for denitrification and organic removal. The Anaerobic Filter with Inoculum, Soft and Hard Packing Medium (AFISH) and Double-Filling Aerobic Baffle (DFAB) reactors were continuously operated for 120 days with a short Hydraulic Retention Time (HRT) in the range of 1 and 2 days at an Organic Loading Rate (OLR) of 0.58 and 1.08 gCOD/(l.d) by daily feeding the influent Chemical Oxygen Demand (COD) concentration between 1169 and 250 mg/l. After treating the sample wastewater in the new AFISH reactor, the effluent flowed into the DFAB reactor for further treatment to determine the treatment effectiveness of the novel AFISH and DFAB reactors at a short HRT of 1 to 2 days. The influent COD was reduced to 376 mg/l to 250 mg/l in a novel AFISH effluent and further dropped to 220 mg/l to 102 mg/l following DFAB reactor treatment. The COD removal in the AFISH reactor was around 67% when HRT was about 1 day, and a high COD value of 78% was removed during the HRT of 2 days, while in the DFAB reactor, the capability of treatment reached between 40% and 57% of the COD removed at the HRT of 1 and 2 days. The concentration of NH4-N in the effluent of the novel AFISH reactor was significantly lower than the effluent of the DFAB reactor, with NH4-N concentrations ranging from 157 mg/l to 330 mg/l. However, the treatment of vegetable bio-slurry from the Internal Circulation (IC) reactor by the novel AFISH and DFAB reactors satisfied the secondary wastewater discharge standard in the Integrated Wastewater Discharge Standard. Therefore, this novel process is one method beneficial for current and further research development that can be applied for industrial wastewater treatment processing and provides science information to those interested in research in the future.

Stable food grade wax/attapulgite superhydrophobic coatings for anti-adhesion of liquid foods

Adhesion of liquid foods on their packaging materials has caused significant food wastes and environment pollution, which has attracted great attention. Food grade superhydrophobic coatings are very promising to solve the issue but suffer from low mechanical stability and complex preparation methods. Herein, a food grade superhydrophobic coating for anti-adhesion of liquid foods was prepared by combining edible paraffin wax, polydimethylsiloxane-modified attapulgite natural nanorods and a food grade silicone adhesive. The concentration of polydimethylsiloxane-modified attapulgite, ultrasonication time and the volume ratio of the paraffin wax/attapulgite suspension to the silicone adhesive solution have great influences on wettability and morphology of the coatings. The coatings exhibit good static and dynamic superhydrophobicity due to their hierarchical micro-/nanostructure and low surface energy of the polydimethylsiloxane-modified attapulgite and paraffin wax. Moreover, the coatings exhibit good mechanical and chemical stability. The coatings are also highly repellent towards various liquid foods including the hot ones. Furthermore, the coatings are applicable onto various frequently used flexible and hard food packing materials including polypropylene, polyethylene terephthalate, aluminium alloy and paper, etc. Thus, the superhydrophobic coatings have great application potential in the food packing industry for anti-adhesion of liquid foods.

New Insights into Segmental Packing, Chain Dynamics and Thermomechanical Performance of Aliphatic Polyurea Composites: Comparison between Silica Oxides and Titanium (III) Oxides

AbstractPolyurea (PU) is intrinsically reinforced by its microphase‐separated morphology, giving its excellent mechanical properties. In this study, it is shown how a high‐index PU formulation applies easy diffusion of hard segments into the soft phase of the PU matrix and tune its chain mobility. Moreover, the interaction of micro (>100 nm), nano (<100 nm) fillers with the microdomains and their thermomechanical properties are unraveled. Herein, nanosilica oxide (NS) and micro titanium (III) oxide (Ti2O3) are incorporated at low loadings into a solvent‐free two‐component aliphatic PU via insitu polymerization. While NS achieves an interfacial interaction with urea groups and forms a tight hard segmental packing, the large‐sized Ti2O3 assembles the interconnected PU chain network, improving its crystallinity. Strong reinforcement by NS is noticed when tensile strength increased from 26 to 31 MPa and on the maximum thermal degradation temperature by 21 °C increment from the neat PU. In contrast, the soft segmental dynamics are triggered with the presence of Ti2O3 as indicated in the reduction in glass transition temperature and the 288% improvement in the storage modulus. This study provides an insightful perspective in designing robust PU composites, effective for myriad applications including strong and flexible films in circuit boards and photovoltaic (PV) cells.

Study on dynamic properties and micro-structure of exceeding lean RCC

In recent years, exceeding lean RCC has been widely used in the quality structure of hydraulic buildings due to its advantages of low cost and environmental friendliness. In order to study the dynamic characteristics of exceeding lean RCC under seismic action, cyclic loading test is carried out. According to the test results, the elasticity of the stress-strain relationship was determined by cyclic loading test under the condition that the maximum compressive stress did not exceed the linear range of the hard packing. On this basis, the linear range of cyclic load exceeding the limit of lean concrete is analyzed. In addition, the reaction products of each sample were tested, and it was found that ettringite with typical acicular structure was produced after adding cement. The micro-structure of exceeding lean RCC was studied by SEM and EDS.

A Method of Large-Scale Resource Utilization of Algae—Eutrophic Waste from Lake Chao, China: Preparation and Performance Optimization of Composite Packaging Materials

In order to realize the resource utilization of bloom algae from Lake Chao, this study presents the use of fresh algae to improve the mechanical and biological properties of low-density polyethylene (LDPE). In this study, the algae and LDPE were used as raw materials, maleic anhydride grafted polyethylene (PE-g-MAH), polyethylene wax (PE-wax) and white oil, and glycerin were used as the compatibilizer, lubricant, and plasticizer, respectively. The single factor experiments were conducted with these three individual factors, and the response surface methodology technique was used to optimize the process conditions. In the single factor experiments, the mechanical properties of the composites increased with additions of PE-g-MAH, PE-wax/white oil, and glycerin. Both flexural strength and flexural modulus were maximized to optimize the preparation conditions. The optimum preparation conditions were found as follows: algae powder of 15.00 wt%, LDPE of 85.00 wt%, PE-g-MAH of 4.00 wt%, lubricant of 2.67 wt%, and glycerin of 3.00 wt%. This resulted in 11.60 MPa of tensile strength, 9.95 MPa of flexural strength, and 241.00 MPa of flexural modulus. The mechanical properties of composites were greatly improved compared with the absence of additives. In addition, compared with LDPE resin, the degradability of the composite was improved, and the weight loss rate was 7.73% after 6 months. The results recommended that the composites of the algae from Lake Chao and LDPE resin could be a useful material in the packaging field. Generally, the prepared composite particles can be used to produce foam products, packaging bags, or hard packing boxes with special shapes. It is more environmentally friendly, and more able to meet the challenges of sustainable development.

Development of a Naturally Flavored Ready to Serve (RTS) Fruit Beverage

Fruit based beverages are one of the foremost categories of beverages that are consumed globally. Since fruit beverages are easily digestible, health conscious, highly refreshing, thirst quenching, appetizing and nutritionally far superior to most of the synthetic beverages available in the market, consumption of fruit based beverages have been increased dramatically. Natural extracts of tropical fruits such as Carica papaya (papaya), Passiflora edulis (passion fruit), and natural flavor extract of Camellia sinensis (leaves) and Cinnamomum verum (Cinnamon barks) were extracted and used as the main ingredients of this product while sugar, Citric acid, pectin were used as the supplementary ingredients. The best fruit pulp ratio and the best natural flavoring agent out of tea and cinnamon was determined through structured sensory evaluations by participating 30 semi trained panelists. Further experiments were also performed to find the optimum amount of pectin to reduce hard packing and to determine the shelf life of the developed beverage and to develop the natural pectin extraction method by using unutilized parts of the Passiflora edulis fruit. Proximate analysis studies and microbiological studies were also carried out. Collected data were statistically analyzed using Kruskal-Wallis non parametric analysis and sample 293 which is containing 15% total fruit pulp with papaya to passion fruit ratio 2:1 and cinnamon as the flavoring agents was the best product formulae. According to the proximate analysis data, fat, protein, carbohydrates, fiber and the ash content were 0.41%, 0.11%, 13.13%, 0.052%, 3.028% and 83.27% respectively. The total plate count was 12 cfu/ml and yeast and molds were 0 cfu/ml of the product and Physico-chemical studies reveals that, the product can be preserved for 30 days under 4±1 0C condition. The average pectin percentage of Passiflora edulis and Carica papaya were 6.9 % and 4.5 % respectively.

Development of a Naturally Flavored Ready to Serve (RTS) Fruit Beverage

Fruit based beverages are one of the foremost categories of beverages that are consumed globally. Since fruit beverages are easily digestible, health conscious, highly refreshing, thirst quenching, appetizing and nutritionally far superior to most of the synthetic beverages available in the market, consumption of fruit based beverages have been increased dramatically. Natural extracts of tropical fruits such as Carica papaya (papaya), Passiflora edulis (passion fruit), and natural flavor extract of Camellia sinensis (leaves) and Cinnamomum verum (Cinnamon barks) were extracted and used as the main ingredients of this product while sugar, Citric acid, pectin were used as the supplementary ingredients. The best fruit pulp ratio and the best natural flavoring agent out of tea and cinnamon was determined through structured sensory evaluations by participating 30 semi trained panelists. Further experiments were also performed to find the optimum amount of pectin to reduce hard packing and to determine the shelf life of the developed beverage and to develop the natural pectin extraction method by using unutilized parts of the Passiflora edulis fruit. Proximate analysis studies and microbiological studies were also carried out. Collected data were statistically analyzed using Kruskal-Wallis non parametric analysis and sample 293 which is containing 15% total fruit pulp with papaya to passion fruit ratio 2:1 and cinnamon as the flavoring agents was the best product formulae. According to the proximate analysis data, fat, protein, carbohydrates, fiber and the ash content were 0.41%, 0.11%, 13.13%, 0.052%, 3.028% and 83.27% respectively. The total plate count was 12 cfu/ml and yeast and molds were 0 cfu/ml of the product and Physico-chemical studies reveals that, the product can be preserved for 30 days under 4±1 0C condition. The average pectin percentage of Passiflora edulis and Carica papaya were 6.9 % and 4.5 % respectively.

Effects of Diisocyanate Structure and Disulfide Chain Extender on Hard Segmental Packing and Self-Healing Property of Polyurea Elastomers.

Four linear polyurea elastomers synthesized from two different diisocyanates, two different chain extenders and a common aliphatic amine-terminated polyether were used as models to investigate the effects of both diisocyanate structure and aromatic disulfide chain extender on hard segmental packing and self-healing ability. Both direct investigation on hard segments and indirect investigation on chain mobility and soft segmental dynamics were carried out to compare the levels of hard segmental packing, leading to agreed conclusions that correlated well with the self-healing abilities of the polyureas. Both diisocyanate structure and disulfide bonds had significant effects on hard segmental packing and self-healing property. Diisocyanate structure had more pronounced effect than disulfide bonds. Bulky alicyclic isophorone diisocyanate (IPDI) resulted in looser hard segmental packing than linear aliphatic hexamethylene diisocyanate (HDI), whereas a disulfide chain extender also promoted self-healing ability through loosening of hard segmental packing compared to its C-C counterpart. The polyurea synthesized from IPDI and the disulfide chain extender exhibited the best self-healing ability among the four polyureas because it had the highest chain mobility ascribed to the loosest hard segmental packing. Therefore, a combination of bulky alicyclic diisocyanate and disulfide chain extender is recommended for the design of self-healing polyurea elastomers.

Can a Branch and Bound algorithm solve all instances of SALBP-1 efficiently?

Following the publication by Sewell and Jacobson of a Branch and Bound algorithm which has solved all existing benchmarks for the simple assembly line balancing problem of type 1 (SALBP-1) in less than 1 second per problem, this paper investigates the possible existence of harder instances and how they can be designed. SALBP-1 is a generalization of the bin packing problem. We demonstrate how a hard bin packing case can be generated. We prove that, in the worst case, Branch and Bound algorithms with Lower Bounds computed in polynomial time are unable to solve even moderate sized examples of the problem in appropriate time limit. Branch and Bound is an excellent approach based on decomposition and enumeration. Intelligent techniques were elaborated to avoid a complete enumeration. Nevertheless, as demonstrated here, it is always possible to find cases where a Branch and Bound will necessitate a complete enumeration.

Split Packing: Algorithms for Packing Circles with Optimal Worst-Case Density

In the classic, \(\mathsf {NP}\)-hard circle packing problem, one asks whether a given set of circles can be packed into a given container. In this paper, we present new sufficient conditions for packing circles into square and triangular containers, using only the sum of the circles’ areas: for square containers, it is possible to pack any set of circles with a combined area of up to \(\approx \!\,53.90\%\) of the square’s area. And when the container is a right or obtuse triangle, any set of circles whose combined area does not exceed the triangle’s incircle can be packed. These area conditions are tight: for any larger areas, there are sets of circles which cannot be packed. Similar results have long been known for squares, but to the best of our knowledge, we give the first results of this type for circular objects. Our proofs are constructive: we describe a versatile, divide-and-conquer-based algorithm for packing circles into various container shapes with optimal worst-case density, which employs an elegant, recursive subdivision scheme. We call this algorithm Split Packing. It can be used as a constant-factor approximation algorithm when looking for the smallest container in which a given set of circles can be packed, due to its polynomial runtime. A visualization can be found at https://morr.cc/split-packing/.

Generalized packing radius theorems of Alexandrov spaces with curvature ≥ 1

In this paper, we give some generalized packing radius theorems of an [Formula: see text]-dimensional Alexandrov space [Formula: see text] with curvature [Formula: see text]. Let [Formula: see text] be any [Formula: see text]-separated subset in [Formula: see text] (i.e. the distance [Formula: see text] for any [Formula: see text]). Under the condition “[Formula: see text]” (after [K. Grove and F. Wilhelm, Hard and soft packing radius theorems, Ann. of Math. 142 (1995) 213–237]), we give the upper bound of [Formula: see text] (which depends only on [Formula: see text]), and classify the geometric structure of [Formula: see text] when [Formula: see text] attains the upper bound. As a corollary, we get an isometrical sphere theorem in Riemannian case.

Approximating polyhedra with sparse inequalities

In this paper, we study how well one can approximate arbitrary polytopes using sparse inequalities. Our motivation comes from the use of sparse cutting-planes in mixed-integer programing (MIP) solvers, since they help in solving the linear programs encountered during branch-&-bound more efficiently. However, how well can we approximate the integer hull by just using sparse cutting-planes? In order to understand this question better, given a polyope $$P$$P (e.g. the integer hull of a MIP), let $$P^k$$Pk be its best approximation using cuts with at most k non-zero coefficients. We consider $${\text {d}}(P, P^k) = \max _{x \in P^k} \left( \min _{y \in P} \Vert x - y\Vert \right) $$d(P,Pk)=maxx?Pkminy?P?x-y? as a measure of the quality of sparse cuts.In our first result, we present general upper bounds on $${\text {d}}(P, P^k)$$d(P,Pk) which depend on the number of vertices in the polytope. Our bounds imply that if $$P$$P has polynomially many vertices, using half sparsity already approximates it very well. Second, we present a lower bound on $${\text {d}}(P, P^k)$$d(P,Pk) for random polytopes that show that the upper bounds are quite tight. Third, we show that for a class of hard packing IPs, sparse cutting-planes do not approximate the integer hull well, that is $$d(P, P^k)$$d(P,Pk) is large for such instances unless k is very close to n. Finally, we show that using sparse cutting-planes in extended formulations is at least as good as using them in the original polyhedron, and give an example where the former is actually much better.

Geometric Models for Isotropic Random Porous Media: A Review

Models for random porous media are considered. The models are isotropic both from the local and the macroscopic point of view; that is, the pores have spherical shape or their surface shows piecewise spherical curvature, and there is no macroscopic gradient of any geometrical feature. Both closed-pore and open-pore systems are discussed. The Poisson grain model, the model of hard spheres packing, and the penetrable sphere model are used; variable size distribution of the pores is included. A parameter is introduced which controls the degree of open-porosity. Besides systems built up by a single solid phase, models for porous media with the internal surface coated by a second phase are treated. Volume fraction, surface area, and correlation functions are given explicitly where applicable; otherwise numerical methods for determination are described. Effective medium theory is applied to calculate physical properties for the models such as isotropic elastic moduli, thermal and electrical conductivity, and static dielectric constant. The methods presented are exemplified by applications: small-angle scattering of systems showing fractal-like behavior in limited ranges of linear dimension, optimization of nanoporous insulating materials, and improvement of properties of open-pore systems by atomic layer deposition of a second phase on the internal surface.

Nature inspired genetic algorithms for hard packing problems

This paper presents two novel genetic algorithms (GAs) for hard industrially relevant packing problems. The design of both algorithms is inspired by aspects of molecular genetics, in particular, the modular exon-intron structure of eukaryotic genes. Two representative packing problems are used to test the utility of the proposed approach: the bin packing problem (BPP) and the multiple knapsack problem (MKP). The algorithm for the BPP, the exon shuffling GA (ESGA), is a steady-state GA with a sophisticated crossover operator that makes maximum use of the principle of natural selection to evolve feasible solutions with no explicit verification of constraint violations. The second algorithm, the Exonic GA (ExGA), implements an RNA inspired adaptive repair function necessary for the highly constrained MKP. Three different variants of this algorithm are presented and compared, which evolve a partial ordering of items using a segmented encoding that is utilised in the repair of infeasible solutions. All algorithms are tested on a range of benchmark problems, and the results indicate a very high degree of accuracy and reliability compared to other approaches in the literature.

On near-wall effects in hard disk packing between two concentric cylinders

Monodisperse packing of disks in confined geometries is rarely addressed in the literature. We present some theoretical aspects of the microstructural properties of 2D static packing of disks between two concentric cylinders. In the core of the geometry, the packing is intact, while it is dilated in the vicinity of the walls as a result of the removal of overlapping disks. We have derived the formula for average packing density in concentric cylinders geometry with given ratio of the particle diameter to the gap between cylinders. It is verified and analyzed further by constructing ordered and disordered packs of monodisperse disks in computer. In this context, Voronoi tessellation is performed for the resulting packs to demonstrate the thickness of the static boundary layer where the packing is influenced by the presence of cylindrical walls.

Conformational variability exhibited by mellitic acid anions (MA−n) with organic amine cations: Structures with an abundance of NH ⋅s OC hydrogen bonds and a paucity of hydrogen bonds

Benzenehexacarboxylic acid (mellitic acid) is an ideal substrate for the study of radially arranged ionic interactions with organic bases. Earlier work has shown that the net charge in MA (−4, −3, or −2) influences its assembly, respectively, either as ribbons or sheets. In the former case the cations intersperse the ribbons forming a tight network. In the MA sheets from the latter, the cations are arranged in orthogonal stacks. In the MA-phenanthroline complex such stacks are arranged exactly parallel resulting in significant π–π interactions. The present work relates to the modification of the phenanthroline motif to flexible structures. The reported ability of 2,3-bis-(2′-pyridyl) pyrazine (P2), prepared from 2,2′-pyridyl by reaction with ethylenediamine (EDA) followed by dehydrogenation of the resulting 2,3-bis-(2′-pyridyl)-5,6-dihydropyrazine, to form helical structures made it an obvious choice for complexation studies with MA. These resulted not only in the formation of the desired 7 MAP2 complex but also, surprisingly, with the dihydroprecursor complex with EDA 3 (MAEDA), a compound that eluded direct preparation with MA and EDA. The crystal structure of MAEDA reports the first complex of MA where MA−5 ions are encountered. The 15 hydrogen bonds, three for each N, result in hard packing. The complex with P2 7 (MAP2) showed the common features of MA−2 sheets. Unlike phenanthroline, the nonplanar disposition of the pyridine rings made it possible for both pyridine protons to be available for salt formation, resulting in the arrangement of the cations in layers interposed between the sheets of MA−2 ions. The pyrazine ring does not participate in hydrogen bonding or stacking in the crystal.

Random covering of the circle: the configuration-space of the free deposition process

Consider a circle of circumference 1. Throw at random n points, sequentially, on this circle and append clockwise an arc (or rod) of length s to each such point. The resulting random set (the free gas of rods) is a collection of a random number of clusters with random sizes. It models a free deposition process on a 1D substrate. For such processes, we shall consider the occurrence times (number of rods) and probabilities, as n grows, of the following configurations: those avoiding rod overlap (the hard-rod gas), those for which the largest gap is smaller than rod length s (the packing gas), those (parking configurations) for which hard rod and packing constraints are both fulfilled and covering configurations. Special attention is paid to the statistical properties of each such (rare) configuration in the asymptotic density domain when ns = ρ, for some finite density ρ of points. Using results from spacings in the random division of the circle, explicit large deviation rate functions can be computed in each case from state equations. Lastly, a process consisting in selecting at random one of these specific equilibrium configurations (called the observable) can be modelled. When particularized to the parking model, this system produces parking configurations differently from Renyi's random sequential adsorption model.

Thermotropic Behavior of Lipophilic Derivatized [60]Fullerenes Studied by Deuterium NMR, X-ray Diffraction, and Microcalorimetry

The dynamics, structure, and thermotropic behavior of a new class of lipophilic [60]fullerene (C60) derivatives, so-called lipo-fullerenes, have been studied by differential scanning calorimetry (DSC), deuterium nuclear magnetic resonance (2H NMR), and X-ray scattering. The lipo-fullerene studied consists of six pairs of perdeuterated C18 alkyl chains as substituents of six covalently attached methylene groups in octahedral sites. The symmetry of this highly symmetrical hexamethanofullerene is Th. We find drastic changes of the molecular arrangement of the lipo-fullerenes induced by temperature. Heating the sample from 20 to 70 °C causes it to undergo two major structural transitions. At 55 °C we observe an exothermic transition from a low-temperature, hard sphere-like packing state of the molecules, with separation distances (6.1 nm) slightly above the maximum diameter of the molecules, to a condensed one. This latter state involves partial intercalation (interdigitation) of the alkyl chains belonging to adjacent molecules and is preceded by partial melting of the chains to accommodate sterically for the (exothermic) interdigitation. The latter allows denser packing with an average separation distance of 4.8 nm. At a temperature of 64 °C, an endothermic melting transition from the interdigitated to a viscous fluidlike state is observed, with an average separation distance of 2.8 nm. Cooling the sample from 70 °C causes a direct transition from the fluid into the low-temperature state with no interdigitation of the chains.

The crystal structure of the β″ phase in Al–Mg–Si alloys

The crystal structure of β″, one of the strengthening phases in the commercially important Al–Mg–Si alloys, is determined by use of high resolution electron microscopy (HREM) and electron diffraction (ED). A trial structure was established from exit wave phase reconstructed HREM images. A least-square refinement of the model coordinates was done using data from digitally recorded ED patterns. A recently developed computer program (MSLS) was applied, taking into account dynamic scattering. The atomic unit cell contains two units of Mg 5Si 6. It is C-centred monoclinic, space group C2/m, a=1.516±0.002 nm, b=0.405 nm, c=0.674±0.002 nm, β=105.3±0.5°. The atomic packing may be regarded as a hard ball packing using clusters, the clusters being (1) centred tetragons of Mg atoms and (2) so-called twin icosacaps where Mg atoms are centred above and below pentagonal rings of four Si atoms an one Mg atom. A growth related stacking fault in the structure is explained by a deficiency of Mg atoms. A model for the β″/Al interface is given.

Hard and Soft Packing Radius Theorems

Singular spaces are playing an increasingly important role in Riemannian geometry. In particular this is true of the so-called Alexandrov spaces; i.e., finite-(Hausdorff) dimensional, complete, inner metric spaces with a lower curvature bound in the local triangle comparison sense. Interest in Alexandrov spaces is largely explained by the fact that the natural process of taking Gromov-Hausdorff limits is closed in Alexandrov geometry but not in Riemannian geometry. This simple observation has become a powerful tool in Riemannian geometry (see, for example, [FY], [GP2], or [GPW] and [Pe]). In this paper, we use a new means to obtain results in Riemannian geometry by studying Alexandrov spaces. The operation of forming spherical suspensions of positively curved spaces, an operation which is also closed in Alexandrov geometry but not in Riemannian geometry, will be applied to prove a differentiable sphere theorem which is unlike all previous solutions to the following basic problem.