Constitutive Model and Deformation Characteristics of a Throat Insert Made of the C/C Composite

Axial braided C/C composite materials are widely applied in the throat insert of solid rocket motors. It is the key for the development and design of solid rocket motors to characterize accurately the macromechanical properties of the materials. The Jones-Nelson model is employed to characterize the constitutive relation of the axial braided C/C composite material in this paper. The Jones-Nelson model is expanded and modified to characterize the C/C composite under complex load conditions. The typical external load tests were carried out to verify the accuracy. On this basis, the deformation features of the axial braided C/C composite throat insert are investigated during the working process of motors, and the strain of the throat insert during the working process is obtained by FEM. The strain and temperature in the outer surface of the throat insert are measured in the ground test of motors and are compared with the numerical results by FEM to verify the accuracy of the model. The results show that the result calculated based on the modified Jones-Nelson model by FEM is in a good agreement with the test result. It shows that the modified Jones-Nelson model can better describe the constitutive relation of C/C composite materials, and it can be promoted to the engineering application of the throat insert of solid rocket motors.

Aplication of Liqu Quese for Light Weight Brick Transportation (Case Study at PT Priority One Indonesia Krikilan No. 28, Driyorejo District, Gresik Regency)

At the location of public queuing services, there are often many customers lining up to be served immediately. This problem also exists in the process of transporting light bricks at PT. Priority One Indonesia. It is not efficient because of the time they can spend doing more important things. In this case, a technology is needed to make it easier for customers to queue. In this study, a web-based or online queuing application called the LiQu application was designed. The output of the LiQu application system is to make the queuing process can be done online, and to conduct customer satisfaction research on the performance of the light brick transportation queue service at PT. Priority One Indonesia. Then perform 2 analysis tests, namely Usability analysis calculating the results of the questionnaire using the Likert Scale Inteval method and Reliability analysis with WAPT 3.1 software testing then calculations using the Nelson model.

Evaluation of Lead (Pb(II)) Removal Potential of Biochar in a Fixed-bed Continuous Flow Adsorption System

Background. Lead (Pb(II)) exposure from drinking water consumption is a serious concern due to its negative health effect on human physiology. A commercially available filter uses the adsorption potential of activated carbon for removing heavy metals like Pb(II). However, it has some constraints since it uses only surface area for the adsorption of these contaminants. Biochar produced via slow pyrolysis of biomass shows the presence of oxygen-containing functional groups on its surface that take part in the adsorption process, with higher removal potential compared to activated carbon. Objectives. The current study examined the adsorption kinetics and mechanisms of Pb(II) removing potential of biochar from water using a fixed-bed continuous flow adsorption system. Methods. The effect of initial Pb(II) concentration, mass of adsorbent (bed depth), and flow rate on adsorption potential were evaluated. The Adams-Bohart model, Thomas model, and Yoon-Nelson model were applied to the adsorption data. Results. The maximum removal efficiency of Pb(II) was 88.86 mg/g. The result illustrated that the Yoon-Nelson model is the best fit to analyze the adsorption phenomena of Pb(II) in a fixed-bed biochar column. Conclusions. The breakthrough data obtained from this study can be utilized to design a point of use filter that would be able to effectively remove Pb(II) from drinking water. Competing Interests. The authors declare no competing financial interests.

On the Self-Adjointness of H+A∗+A

Let $H:\text {dom}(H)\subseteq \mathfrak {F}\to \mathfrak {F}$ H : dom ( H ) ⊆ F → F be self-adjoint and let $A:\text {dom}(H)\to \mathfrak {F}$ A : dom ( H ) → F (playing the role of the annihilation operator) be H-bounded. Assuming some additional hypotheses on A (so that the creation operator A∗ is a singular perturbation of H), by a twofold application of a resolvent Kreı̆n-type formula, we build self-adjoint realizations $\widehat H$ H ̂ of the formal Hamiltonian H + A∗ + A with $\text {dom}(H)\cap \text {dom}(\widehat H)=\{0\}$ dom ( H ) ∩ dom ( H ̂ ) = { 0 } . We give an explicit characterization of $\text {dom}(\widehat H)$ dom ( H ̂ ) and provide a formula for the resolvent difference $(-\widehat H+z)^{-1}-(-H+z)^{-1}$ ( − H ̂ + z ) − 1 − ( − H + z ) − 1 . Moreover, we consider the problem of the description of $\widehat H$ H ̂ as a (norm resolvent) limit of sequences of the kind $H+A^{*}_{n}+A_{n}+E_{n}$ H + A n ∗ + A n + E n , where the An’s are regularized operators approximating A and the En’s are suitable renormalizing bounded operators. These results show the connection between the construction of singular perturbations of self-adjoint operators by Kreı̆n’s resolvent formula and nonperturbative theory of renormalizable models in Quantum Field Theory; in particular, as an explicit example, we consider the Nelson model.

Adsorption Kinetics and Equilibrium Isotherms Modeling of H2S on Hydrogel Biochar and Biochar Adsorbent from Rice Husk

Hydrogen sulphide is a poisonous gas that is commonly found in swamps and areas of high volcanic activities. Due to the dangers and hazards that it may impose such as neurological disorders and miscarriages, continuous innovative attempts to remove the gas are in place. A study was conducted to synthesize an adsorbent that is made from activated rice husk biochar and also hydrogel biochar. This study is complementary to that study where the adsorption processes using the two adsorbents are mathematically modelled. Three parameters were studied which were the adsorbent mass, the gas flow rate, and the gas temperature. It was found that for rice husk-based activated biochar, for all three parameters, the adsorption processes could be mathematically represented using Thomas Model and Yoon-Nelson Model. Meanwhile, for rice husk-based hydrogel biochar, the adsorption process could be mathematically represented using Thomas and Yoon-Nelson Model for the effect of mass of adsorbent, and Adam-Bohart for the effect of gas flow rate and gas temperature. Although the coefficient of determination (R2) suggested that Thomas and Yoon-Nelson Model are more appropriate to be used to model the latter two parameters, because the exit concentration reached the point when it was greater than half the inlet concentration well before 0-th second, the linearly regressed equation became mathematically inconsistent with the isotherm models. Kinetic studies were also done, and it was found that the adsorption processes using the activated biochar fit both pseudo-first and pseudo-second order equation. This means that the adsorption processes using the activated biochar are both physisorption and chemisorption. Meanwhile, the adsorption processes using the hydrogel biochar fit only the pseudo-second order equation, suggesting that the adsorption process is chemisorption.