Strain-shear coupling in bilayer MoS2

Layered materials such as graphite and transition metal dichalcogenides have extremely anisotropic mechanical properties owing to orders of magnitude difference between in-plane and out-of-plane interatomic interaction strengths. Although effects of mechanical perturbations on either intra- or inter-layer interactions have been extensively investigated, mutual correlations between them have rarely been addressed. Here we show that layered materials have an inevitable coupling between in-plane uniaxial strain and interlayer shear. Because of this, the uniaxial in-plane strain induces an anomalous splitting of the degenerate interlayer shear phonon modes such that the split shear mode along the tensile strain is not softened but hardened contrary to the case of intralayer phonon modes. We confirm the effect by measuring Raman shifts of shear modes of bilayer MoS2 under strain. Moreover, by analyzing the splitting, we obtain an unexplored off-diagonal elastic constant, demonstrating that Raman spectroscopy can determine almost all mechanical constants of layered materials.Comment: 36 pages, 10 figure

Emergent localized states at the interface of a twofold PT\mathcal{PT}-symmetric lattice

We consider the role of non-triviality resulting from a non-Hermitian Hamiltonian that conserves twofold PT-symmetry assembled by interconnections between a PT-symmetric lattice and its time reversal partner. Twofold PT-symmetry in the lattice produces additional surface exceptional points that play the role of new critical points, along with the bulk exceptional point. We show that there are two distinct regimes possessing symmetry-protected localized states, of which localization lengths are robust against external gain and loss. The states are demonstrated by numerical calculation of a quasi-1D ladder lattice and a 2D bilayered square lattice.Comment: 10 pages, 7 figure

Microstructure and thermal conductivities of suspension vacuum plasma sprayed YSZ coatings

To increase the efficiency of gas turbine, the turbine inlet temperature should increase. As the turbine inlet temperature increases, the heat load of thermal barrier coating increases. Suspension plasma spraying(SPS) was developed to enhance the performance of thermal barrier coating. Suspension allows nano-sized powders to be injected into the plasma flame, which has advantage of forming a variety of microstructures. However, there is a disadvantage of SPS that cannot be completely transmitted the enthalpy of plasma flame due to evaporation of solvent in the suspension, which causes decrement of coating formation rate. In this study, disadvantages of the suspension atmospheric plasma spraying(SAPS) can be solved by forming YSZ coatings through suspension vacuum plasma spraying(SVPS). The length of plasma flame in vacuum condition becomes longer, powders can stay longer inside the plasma flame. A variety of microstructured YSZ coatings were formed by SPVS at various spraying conditions. Microstructure of SVPS YSZ coatings were analyzed by SEM. Thermal conductivity of SVPS YSZ coatings were analyzed by laser flash method. Coating formation rate showe

Efficient High-dimensional Quantum Key Distribution with Hybrid Encoding

We propose a schematic setup of quantum key distribution (QKD) with an improved secret key rate based on high-dimensional quantum states. Two degrees-of-freedom of a single photon, orbital angular momentum modes, and multi-path modes, are used to encode secret key information. Its practical implementation consists of optical elements that are within the reach of current technologies such as a multiport interferometer. We show that the proposed feasible protocol has improved the secret key rate with much sophistication compared to the previous 2-dimensional protocol known as the detector-device-independent QKD.Comment: 10 pages, 6 figure

Clinicopathological Characteristics of Male Breast Cancer

PURPOSE: To investigate clinicopathological characteristics and outcomes of male breast cancer (MBC). PATIENTS AND METHODS: We retrospectively analyzed the data of 20 MBC patients in comparison with female ductal carcinoma treated at Yonsei University Severance Hospital from July 1985 to May 2007. Clinicopathological features, treatment patterns, and survival were investigated. RESULTS: MBC consists of 0.38% of all breast cancers. The median age was 56 years. The median symptom duration was 10 months. The median tumor size was 1.7 cm, 27.8% showed node metastasis, and 71.4% were estrogen receptor positive. All 20 cancers were arisen from ductal cells. No lobular carcinoma was found. The incidence of stages 0, I, II, and III in patients were 2, 10, 4, and 3, respectively. All patients underwent mastectomy. One with invasive cancer did not receive axillary node dissection and stage was not exactly evaluated. Adjuvant treatments were determined by pathologic parameters and stage. Clinicopathological parameters and survival rates of MBC were comparable to those of female ductal carcinoma. CONCLUSION: The onset age of MBC was 10 years older and symptom duration was longer than in female patients. No difference in outcomes between MBC and female ductal carcinoma suggests that the biology of MBC is not different from that of females. Therefore, education, an appropriate system for early detection, and adequate treatment are necessary for improving outcomes.ope

Analytical Modeling of Rheological Postbuckling Behavior of Wood-Based Composite Panels Under Cyclic Hygro-Loading

This study was conducted to develop analytical models to predict postbuckling behavior of woodbased composite panels under cyclic humidity conditions. Both the Rayleigh method and von Karman theory of nonlinear plate with imperfection were used to obtain a closed form solution to the hygrobuckling and postbuckling. In addition, mechano-sorptive creep effects were also taken into account for the derivation of analytical models. The closed-form solutions derived for both isotropic and orthotropic materials showed a good agreement with the experimental results in terms of the center deformation of hardboard, especially in the case of the edge movements. The unrecovery deformation was much greater at the first cycle and then decreased as the number of cyclic hygro-loading increased