Local Buckling-Induced Forming Method to Produce Metal Bellows

A novel buckling-induced forming method is proposed to produce metal bellows.The tube billet is firstly treated by local heating and cooling,and the axial loading is applied on both ends of the tube,then the buckling occurs at the designated position and forms a convolution.In this paper,a forming apparatus is designed and developed to produce both discontinuous and continuous bellows of 304 stainless steel,and their characteristics are discussed respectively.Furthermore,the influences of process parameters and geometric parameters on the final convolution profile are deeply studied based on FEM analysis.The results suggest that the steel bellows fabricated by the presented buckling-induced forming method have a uniform shape and no obvious reduction of wall thickness.Meanwhile,the forming force required in the process is quite small.

Concrete durability under different circumstances based on multi-factor effects

Concrete durability has become a hot research field in civil engineering. Concrete structures suffer salt-erosion damage to different degrees in the semi-arid region of North China. The environmental condition is one of the important factors affecting the durability of concrete constructions. To realize fully the interaction between various environmental factors, this paper researched concrete durability in the salt environment under combined actions(immersing, freeze–thaw cycles, and wet–dry cycles). According to the laboratory test data, the concrete-durability degradation law under coupling-effect factors was investigated. The results show that concrete's compressive strength decreases with the increase of salt concentration and immersion time. No matter what the environmental conditions were, the compressive strength-loss ratio increased with the test time. The compressive strength-test results indicate that sodium sulfate has the strongest corrosive effect on concrete durability, followed by calcium chloride, with sodium chloride having the weakest corrosion. Compared with the other two environmental factors, the wet–dry cycle is the key factor affecting concrete durability. Therefore, in engineering practice, the influence of environment conditions on the strength and durability of concrete should be taken into full consideration, especially in the wet–dry environment with salt conditions.

An experimental study on the relationship between acoustic parameters and mechanical properties of frozen silty clay

To study the influence of temperature and water content on ultrasonic wave velocity and to establish the relationship between ultrasonic wave velocity and frozen silty clay strength, ultrasonic tests were conducted to frozen silty clay by using RSM-SY5（T） nonmetal supersonic test meter, and the tensile strength and compressive strength of silty clay were measured under various negative temperatures. Test and analysis results indicate that, ultrasonic wave velocity rapidly changes in the temperature range of-1 ℃ to -5 ℃. Ultrasonic wave velocity increased with an increase of water content until the water content reached the critical water content, while decreased with an increase of water content after the water content exceeded the critical water content. This study showed that there was strong positive correlation between the ul- trasonic wave velocity and the frozen soil strength. As ultrasonic wave velocity increased, either tensile strength or com- pressive strength increased. Based on the experimental data, the relationship between ultrasonic wave velocity and frozen silty clay strength was obtained through regression analysis. It was found that the ultrasonic test technique can be used to test frozen soils and lay the foundation for the determination of frozen soil strength.

Comparison of skeletal and soft tissue pericytes identifies CXCR4+ bone forming mural cells in human tissues

Human osteogenic progenitors are not precisely defined,being primarily studied as heterogeneous multipotent cell populations and termed mesenchymal stem cells(MSCs).Notably,select human pericytes can develop into bone-forming osteoblasts.Here,we sought to define the differentiation potential of CD146 f human pericytes from skeletal and soft tissue sources,with the underlying goal of defining cell surface markers that typify an osteoblastogenic pericyte.CD146+CD31~CD45_pericytes were derived by fluorescence-activated cell sorting from human periosteum,adipose,or dermal tissue.Periosteal CD146+CD31—CD45 cells retained canonical features of pericytes/MSC.Periosteal pericytes demonstrated a striking tendency to undergo osteoblastogenesis in vitro and skeletogenesis in vivo,while soft tissue pericytes did not readily.Transcriptome analysis revealed higher CXCR4 signaling among periosteal pericytes in comparison to their soft tissue counterparts,and CXCR4 chemical inhibition abrogated ectopic ossification by periosteal pericytes.Conversely,enrichment of CXCR4+pericytes or stromal cells identified an osteoblastic/non-adipocytic precursor cell.In sum,human skeletal and soft tissue pericytes differ in their basal abilities to form bone.Diversity exists in soft tissue pericytes,however,and CXCR4+pericytes represent an osteoblastogenic,non-adipocytic cell precursor.Indeed,enrichment for CXCR4-expressing stromal cells is a potential new tactic for skeletal tissue engineering.

Experimental study on moisture migration of remodeled clay under different overburden pressure and temperature gradients

Unidirectional freezing experiments under overburden pressure were carried out, in order to study the driving force of mois- ture migration of remodeled clay during freezing, through improving the indoor moisture migration test device. Overburden pressure and cooling temperature with the same circumstance were changed to determine the influence on water migration of a single factor. Results show that water content increases above the location of the final ice lenses and decreases below the loca- tion. When the overburden pressure increases, water intake gradually decreases and the time starting to absorb water is delayed. The location of the final ice lens is not sensitive to overburden pressure but influenced by the temperature boundary. The im- pact of overburden pressure and maximum temperature is not obvious. Freezing rate is not sensitive to overburden pressure but influenced by temperature, and it increases when the cold temperature decreases. Frost heave and water intake flow in- creases with increasing time and rises up to a peak value, and then decreases. During the freezing process, water intake flow increases when freezing rate decreases. Water intake flow decreases when the overburden pressure increases when the cold temperature decreases. Finally, we expanded the segregation theory, and proposed a model to describe the relationship between water intake flow and freezing rate.

Wave propagation characteristics in frozen saturated soil

Ultrasonic detection technology is of great significance in the detection and evaluation of physical and mechanical properties of frozen soil, but wave propagation characteristics in frozen soil are unclear. Based on the three-phase composition of frozen saturated soil and the mixture theory, considering Bishop's effective stress formula, the wave propagation equations are establish for frozen saturated soil. In wave propagation, an entropy inequality was introduced to describe the coupling of different phases. The analytic expressions of propagation velocity and attenuation law of waves in frozen soil are obtained, and wave propagation characteristics in frozen saturated soil are discussed. Results show that four types of waves(i.e., P1, P2, P3 and S) are found in frozen saturated soil and all four wave types are dissipative waves, in which the attenuation of P3 is the maximum. The velocity of four waves increases sharply at the excitation frequency range of 10~3–10~9 Hz,but the wave velocity at high-frequency and low-frequency is almost constant. When volume ice content increases, the wave propagation velocity of P1 and S decreases dramatically, and the velocity of P2 increases gradually, but P3 velocity increases first and then decreases to zero with increasing saturation. The attenuation coefficients of P1 and S waves begins to increase gradually when the volume ice content is about 0.4, P2 increases first and then decreases with an increase of volume ice content and P3 increases with the volume ice content and decreases rapidly from extreme to zero.

Experimental research on acoustic wave velocity of frozen soils during the uniaxial loading process

Ultrasonic P-wave tests of frozen silt and frozen sand were conducted during uniaxial loading by using an RSM^-SY5（T） nonmetal ultrasonic test meter to study the velocity characteristics of P-waves. The experimental results indicate that the P-wave velocity is affected by soil materials, temperature, and external loads, so the P-wave velocity is different in frozen silt and frozen sand, but all decrease with an increase of temperature and increase at first and then decrease with strain during the loading process. There is an exponential relationship between uniaxial compressive strength and P-wave ve- locity, and the correlation between them is very good. The characteristic parameters of acoustic waves can, to some extent, reflect the development of internal cracks in frozen soils during loading.

Specifically Binding of L-ficolin to N-glycans of HCV Envelope Glycoproteins E1 and E2 Leads to Complement Activation

L-ficolin, one of lectin families, is a recently identified complement factor that initiates lectin pathway of complement. Little is known about its role in viral hepatitis. In the present study, we found that L-ficolin in serum from 103 patients with hepatitis C virus （HCV）, were significantly higher than that in 150 healthy controls. We further found that L-ficolin expressions were significantly increased in vitro study by HCV JFH-1 infected human hepatocyte cell line Huh7.5.1. Investigation of the mechanisms of the L-ficolin action on HCV demonstrated that L-ficolin protein could recognize and bind to envelope glycoproteins E1 and E2 of HCV, activating the lectin complement pathway-mediated cytolytic activity in HCV-infected hepatocyte. This interaction between L-ficolin and HCV E1 and E2 glycoproteins was attributed to the N-glycans of E1 and E2. These findings provide new insights into the biological functions of L-ficolin in clinically important hepatic viral diseases.

Isothermal Oxidation Behavior of Dysprosium/S-Doped β-NiAl Alloys at 1200°C

A β--NiAI alloy with normal purity, a S-doped and a Dy and S co-doped （Y-NiAI alloys were prepared by arc-melting and their corresponding S contents were less than 20 ×10-6, 33 ×10-6 and 22 × 10-6, respectively. The isothermal oxidation behavior of the alloys at 1200 ℃ was investigated and the extent of S segregation at the scale-alloy interface was determined by scanning Auger microscopy. S-doping had no significant effect on the phase transformation rate from e- to β-Al2O3, while the addition of Dy retarded this process. For the S- doped alloy, scale rumpling occurred only after 2 h thermal exposure and numerous large voids were observed at the scale-alloy interface where S segregated. In contrast to this, the oxide scale formed on the Dy and S co-doped alloy still remained flat even after 50 h isothermal oxidation and only small voids existed at the interface where S segregation was not detected.