[en] Nucleon spin structure has been an active, exciting and intriguing subject of interest for the last three decades. Recent precision spin-structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure in the valence quark (high- x$) region and improved our understanding of higher-twist effects, spin sum rules and quark-hadron duality. First, results of spin sum rules and polarizabilities in the low to intermediate Q² region are presented. Comparison with theoretical calculations, in particular with Chiral Perturbation Theory (ChPT) calculations, are discussed. Surprising disagreements of ChPT calculations with experimental results on the generalized spin polarizability, Δ_LT, were found. Then, precision measurements of the spin asymmetry, A₁, in the high- x$ region are presented. They provide crucial input for global fits to world data to extract polarized parton distribution functions. The up and down quark spin distributions

[en] More than 99% of the visible matter in the universe are the protons and neutrons. Their internal structure is mostly governed by the strong interaction. Understanding their internal structure in terms of fundamental degrees-of-freedom is one of the most important subjects in modern physics. Worldwide efforts in the last few decades have lead to numerous surprises and discoveries, but major challenges still remain. An overview of the progress will be presented with a focus on the recent studies of the proton and neutron's electromagnetic and spin structure. Future perspectives will be discussed.

[en] Spin-dependent observables have been a powerful tool to probe the internal structure of the nucleon and to understand the dynamics of the strong interaction. Experiments involving spin degrees of freedom have lead to numerous surprises, puzzles and discoveries. The so called 'spin crisis' in the 1980s revealed the limitation of naive quark-parton models and led to intensive worldwide efforts, both experimental and theoretical, to understand the nucleon spin structure. The nucleon spin structrue study has grown frommainly on the longitudinal spin in the last thirty years to recently rapidly increasing interests on the transverse spin.With high intensity and high polarization of both the electron beam and targets, JLab has the world's highest polarized luminosity and the best figure-of-merit for precision spin structure measurements. It has made a strong impact in this subfield of research. This proceeding will highlight JLab Hall A's study in the measurements of the moments of spin structure functions at low-to-intermediate Q2 and in the transverse spin structure.

[en] Highlights of JLab 6 GeV results on spin structure study and plan for 12 GeV program. Spin structure study is full of surprises and puzzles. A decade of experiments from JLab yield these exciting results: (1) valence spin structure; (2) precision measurements of g₂/d₂ - high-twist; (3) spin sum rules and polarizabilities; and (4) first neutron transversity. There is a bright future as the 12 GeV Upgrade will greatly enhance our capability: (1) Precision determination of the valence quark spin structure flavor separation; (2) Precision measurements of g₂/d₂; and (3) Precision extraction of transversity/tensor charge.

[en] Overview of Experimental Study of Nucleon Structure and QCD, with focus on the spin structure. Nucleon (spin) Structure provides valuable information on QCD dynamics. A decade of experiments from JLab yields these exciting results: (1) valence spin structure, duality; (2) spin sum rules and polarizabilities; (3) precision measurements of g₂ - high-twist; and (4) first neutron transverse spin results - Collins/Sivers/A_LT. There is a bright future as the 12 GeV Upgrade will greatly enhance our capability: (1) Precision determination of the valence quark spin structure flavor separation; and (2) Precision extraction of transversity/tensor charge/TMDs.

[en] Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinal polarized parton (quark and gluon) distributions in the nucleon. It has becoming clear that transverse spin and transverse momentum dependent distributions (TMDs) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction. The transverse spin structure and the TMDs are the subject of increasingly intense theoretical and experimental study recently. With a high luminosity electron beam facility, JLab has played a major role in the worldwide effort to study both the longitudinal and transverse spin structure. Highlights of recent results will be presented. With 12-GeV energy upgrade, JLab will provide the most precise measurements in the valence quark region to close a chapter in longitudinal spin study. JLab will also perform a multi-dimensional mapping of the transverse spin structure and TMDs in the valence quark region through Semi-Inclusive DIS (SIDIS) experiments, providing a 3-d partonic picture of the nucleon in momentum space and extracting the u and d quark tensor charges of the nucleon. The precision mapping of TMDs will also allow a detailed study of the quark orbital motion and its dynamics.

[en] Understanding the strong interaction (QCD) in the truly strong ('non-perturbative') region remains a major challenge in modern physics. Nucleon and nuclei provide natural laboratories to study the strong interaction. The quark-gluon structure of the nucleon and nuclei are important by themselves since they are the main (>99%) part of the visible world. With electroweak interaction well-understood, e-p and e-A are clean means to probe the nucleon and nuclear structure and to study the strong interaction (QCD). Inclusive Deep-Inelastic Scattering (DIS) experiments have provided us with the most extensive information on the unpolarized and longitudinally-polarized parton (quark and gluon) distributions (PDFs). It has becoming clear that transverse spin and transverse structure (both transverse spatial structure via generalized parton distributions (GPDs) and transverse momentum structure via transverse- momentum-dependent distributions (TMDs)) study are crucial for a more complete understanding of the nucleon structure and the dynamics of the strong interaction(QCD). The transverse spin, GPDs and TMDs have been the subjects of increasingly intense theoretical and experimental study recently. With 12 GeV energy upgrade, Jefferson Lab (JLab) will provide the most precise multi-dimensional map of the TMDs and GPDs in the valence quark region through Semi-Inclusive DIS (SIDIS) and Deep-Exclusive experiments, providing a 3-d partonic picture of the nucleon in momentum and spatial spaces. The precision information on TMDs and GPDs will provide access to the quark orbital angular momentum and its correlation with the quark and the nucleon spins. The planned future Electron-Ion Collider (EIC) will enable a precision study of the TMDs and GPDs of the sea quarks and gluons, in addition to completing the study in the valence region. The EIC will also open a new window to study the role of gluons in nuclei.

[en] Recent precision spin-structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure at low Q². Results on the neutron spin sum rules and polarizabilities in the low to intermediate Q² region are presented. The Burkhardt-Cuttingham Sum Rule was verified within experimental uncertainties. When comparing with theoretical calculations, results on spin polarizability show surprising disagreements with Chiral Perturbation Theory predictions. Preliminary results on first moments at very low Qs² are also presented.

[en] Nucleon spin structure has been an active, exciting and intriguing subject of interest for the last three decades. Recent precision spin-structure data from Jefferson Lab have significantly advanced our knowledge of nucleon structure at low Q². In particular, it has improved our understanding of spin sum rules and higher-twist effects. First, results of neutron spin sum rules and polarizabilities in the low to intermediate Q² region are presented. Comparison with theoretical calculations, in particular with Chiral Perturbation Theory (ChPT) calculations, are discussed. Surprising disagreements of ChPT calculations with experimental results on the generalized spin polarizability, delta_LTⁿ, were found. Results of precision measurements of the g₂ structure function to study higher-twist effects are presented. The data indicate a significant higher-twist (twist-3 or higher) effect. The second moment of the spin structure functions and the twist-3 matrix element d₂ results were extracted. The high Q² result was compared with a Lattice QCD calculation. Finally, other neutron spin structure results, such as the resonance data for quark-hadron duality study and a precision measurement of the neutron spin asymmetry in the valence quark (high-x) region are briefly discussed.

[en] Metallization of ceramic surface by molten salt reaction is a simple and inexpensive method for improving the brazing property of ceramics. In this paper, the microstructure of the coating on the metallized Si₃N₄ surface produced by molten salt reactions was investigated. The results show that titanium reacted with Si₃N₄ to form a multi-layer structure in the coating. Based on thermodynamics calculations and thermogravimetric analysis, the possible reaction between titanium and Si₃N₄ was discussed. Wetting experiment proved that the metallized Si₃N₄ could be completely wetted by AgCu eutectic alloy. The metallized Si₃N₄ was brazed to 45 steel with a maximum joint strength of 226 MPa